Active Site-Directed Tandem Catalysis on Single Platinum

Subscriber access provided by ECU Libraries

Environmental Processes

Active Site Directed Tandem Catalysis on Single Platinum Nanoparticles for Efficient and Stable Oxidation of Formaldehyde at Room Temperature Mengmeng Huang, Yingxuan Li, Mengwei Li, Jie Zhao, Yunqing Zhu, Chuanyi Wang, and Virender K. Sharma Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.9b01176 • Publication Date (Web): 05 Mar 2019 Downloaded from http://pubs.acs.org on March 8, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 30

Environmental Science & Technology

1

Active Site Directed Tandem Catalysis on Single Platinum Nanoparticles for

2

Efficient and Stable Oxidation of Formaldehyde at Room Temperature

3

4

5

6

Mengmeng Huang,† Yingxuan Li,†* Mengwei Li,† Jie Zhao,† Yunqing Zhu,† Chuanyi Wang,†

7

Virender K. Sharma‡*

8 9 10

11

†School

of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China

12 13

‡Program

for the Environment and Sustainability, Department of Occupational and

14

Environmental Health, School of Public Health, Texas A&M University, College Station, Texas

15

77843, USA

16 17 18 19

*To whom correspondence should be addressed.

20

Email: [email protected] (Y. Li) and [email protected] (V.K. Sharma)

21

1 Environment ACS Paragon Plus


22

ABSTRACT: The application of tandem catalysis is rarely investigated in degrading organic

23

pollutants in environment. Herein, a tandem catalyst on single platinum (Pt) nanoparticles (Pt0

24

NPs) is prepared for sequential degrading formaldehyde (HCHO) to carbon dioxide gas (CO2(g))

25

at room temperature. The synthesis approach includes coating of uniform Pt NPs on SrBi2Ta2O9

26

platelets using a photoreduction process, followed by calcination of the sample in atmosphere to

27

tune partial transformation of Pt0 atoms to Pt2+ ions in the tandem catalyst. The conversion of

28

HCHO to CO2(g) is monitored by in situ Fourier transform infrared spectroscopy, which shows

29

first conversion of HCHO to CO32- ions onto Pt0 active sites and subsequently the conversion of

30

CO32- ions to CO2(g) by neighboring Pt2+ species of the catalyst. The later process by Pt2+ species

31

do not allow CO32- poisoning of the catalyst. The enhanced activity of the prepared tandem

32

catalyst to oxidize HCHO is maintained continuously for 680 min. Comparatively, the catalyst

33

without Pt2+ shows the activity only for 40 min. Additionally, the tandem catalyst presented in

34

this paper has better performance than Pt/titanium dioxide (TiO2) catalyst to degrade HCHO.

35

Overall, the tandem catalyst may be applied to degrade organic pollutants efficiently.

36 37 38 39 40


Page 2 of 30

Page 3 of 30

42


INTRODUCTION

43

Formaldehyde (HCHO) is widely recognized as a harmful indoor volatile organic

44

compound because it is commonly released from various building materials, furnishings, and

45

consumer products, causing serious health problems such as eye irritation, respiratory tract

46

irritation, nasal tumors, and even cancer.1,2 To date, various strategies have been shown to

47

remove HCHO at room-temperature, which included physical adsorption, plasma technology,

48

and thermal catalytic oxidation.3−9 The application of oxidation processes using catalysts must

49

have practical aspects such as need of low energy consumption, high activity, and persistent

50

stability.10 Among the various catalysts, supported platinum (Pt) catalysts consist of Pt metallic

51

(Pt0) nanoparticles (NPs) has recently triggered extraordinary interest to oxidize HCHO because

52

of their effectiveness at room temperature that save energy and also generate environmental

53

friendly oxidized products (CO2(g) and H2O).11−15

54

The efficiency of the Pt0 NPs is largely limited because of the strict requirement of small

55

average size and narrow size distribution to adsorb substrate (i.e., HCHO). However,

56

synthesizing such Pt0 NPs by traditional methods is still a great challenge.16 Recently, the

57

positive effect of ferroelectric polarization on photochemical growth of metal NPs has attracted

58

interest.17−24 The spontaneous polarization in ferroelectric materials such as SrBi2Nb2O9 has a

59

significant impact on the nature of photoreduction process.25,26 The polarization bound charges

60

on the surface of the ferroelectric materials can provide uniform sites for the reduction and

61

nucleation of the metal NPs, which is beneficial for monodispersely loading metal NPs.

62

Furthermore, the preparatory methods of Pt0 NPs always yield both Pt0 and Pt oxides (or Pt2+

63

species).14,15 Pt2+ species on Pt0 NPs give negative effect to oxidize HCHO because Pt0 is

64

generally provides catalytic sites to activate O2 to perform oxidation process.27,28 In the present



65

paper, we have coated uniform Pt0 NPs on ferroelectric SrBi2Ta2O9 (SBT) platelets using a

66

photoreduction process, and a strategy of tandem catalysis was developed for the first time to

67

oxidize HCHO efficiently by selectively introducing Pt2+ species into Pt0 NPs.

68

In literature, the tandem catalysis mechanism has received sustained attention in chemical

69

synthesis, in which multiple reactions occur sequentially and selectively in one operation.29–31

70

Traditionally, the tandem catalyst is a complex system containing multiple components and the

71

different interfaces with the corresponding active sites can carry out sequentially coupling the

72

multiple reactions.29–31 However, effectively integrating active sites with different functions into

73

a single nanoparticle that work independently is critical. Additionally, fabricating a catalyst with

74

such properties is an enormous challenge. In the current paper, we used an approach of a

75

photoreduction process under ferroelectric polarization, which enabled us to synthesize tandem

76

catalyst (Pt/SBT) successfully that consisted integrating Pt0 and Pt2+ species to degrade HCHO

77

efficiently. The tandem catalytic mechanism was demonstrated by in situ Fourier transform

78

infrared spectroscopy studies, which could establish Pt0 and Pt2+ species acted as cooperative

79

active sites to carry out two distinct sequential steps of HCHO → CO32− and CO32− → CO2(g),

80

respectively. The study presented herein provides new insights into the fundamental

81

understanding of the microscopic mechanism of the oxidation of HCHO by Pt-based catalysts.

82 83

MATERIALS AND METHODS

84

Synthesis and characterization. Synthesis of SrBi2Ta2O9 (SBT) was carried out by a

85

molten salt method according to the previously reported procedure.32 The details are given in

86

Text S1 (Supplementary Information). Pt0 NPs were synthesized by using a photodeposition

87

method (Text S2, Supplementary Information). The nominal weight percentage ratios of Pt-to-

88

SBT in Pt/SBT samples were 0.5%, 1%, 2%, and 2.5%. The resultant catalysts are denoted as X4 Environment ACS Paragon Plus

Page 4 of 30

Page 5 of 30


89

Pt/SBT (X is the actual weight percentage ratios of Pt-to-SBT, which were 0.44%, 0.9%, 1.5%,

90

and 1.63%) and 1.5%-Pt/SBT-x (x represent the further calcination temperature of the 1.5%-

91

Pt/SBT sample, which were 300, 400, or 500 °C).

92

Characterization. The Pt content in the catalyst was determined by inductively coupled plasma-

93

atomic emission spectroscopy (ICP-6000 SERIES). X-ray diffraction (XRD) patterns of the

94

samples were measured using a MSAL-XD2 X-ray diffractometer equipped with Ni-filtered Cu

95

Kα radiation (λ = 0.1541 nm), and the data were recorded at a scan rate of 4 degrees min−1.

96

Morphology images of the samples were acquired utilizing scanning electron microscopy (SEM)

97

(JSM-6510 microscope, Japan). High-resolution transmission electron microscopy (HRTEM)

98

imaging and high-angle annular dark-field scanning transmission electron microscopy (HAADF-

99

STEM) measurements were performed on a FEI Tecnai F20 microscope at 200 kV. The

100

corresponding particle size distribution was carried out by taking the geometric mean of two

101

orthogonal measurements, based on TEM images. To construct the corresponding particle size

102

distribution histogram of Pt NPs, sizes of 100 particles were measured. Fractional frequency was

103

calculated by dividing the particle count within a size range by the total particle count of the

104

sample. The chemical states of surface elements on the catalysts were measured with X-ray

105

photoelectron spectroscopy (Kratos AXIS Supra, USA). The reference binding energy was the C

106

1s signal at 284.6 eV. In situ Fourier transform infrared (FT-IR) spectroscopy (VERTEX 70v,

107

Bruker) was used to detect the intermediates during the oxidation of HCHO. Background signals

108

were subtracted at the beginning of the in situ FT-IR tests. The BET surface area of SBT

109

powders was determined by nitrogen adsorption using a Micromeritics ASAP 2460 nitrogen

110

adsorption apparatus (USA). The sample was degassed at 150 °C prior to nitrogen adsorption

111

measurements.



112

Degradation of HCHO. An airtight reactor of 500 mL was used to evaluate the catalytic

113

performance of the as-prepared samples toward HCHO degradation. Fresh catalyst powders (0.3

114

g) were uniformly dispersed on a glass dish with a diameter of 45 mm. After the sample-

115

containing dish was fixed in the reactor, a mixture gas of O2 + H2O + 100 ppm HCHO was

116

injected into the reactor. HCHO oxidation was performed under constant stirring with a

117

polytetrafluoroethylene stirrer 20 mm in diameter (1000 rpm/min). During the reaction process,

118

the temperature inside the reactor was maintained at 25 °C. The concentrations of HCHO and

119

CO2 (ppm) were determined by an online Photoacoustic IR Multigas Monitor (INNOVA Air

120

Tech Instruments Model 1412). In the recycling experiments, the catalyst powders were heated

121

at 100 °C for 60 min to remove the adsorbed molecules prior to carrying out the subsequent

122

oxidation of HCHO.

123 124

RESULTS AND DISCUSSION

125

Oxidation activity of catalysts. Initially, oxidation of HCHO over Pt/SBT catalysts containing

126

different weight percentage ratios of Pt (0.44%, 0.9%, 1.5%, and 1.63%) was investigated at

127

room temperature by monitoring decay of HCHO and concomitant formation of CO2(g) (Figures

128

1a,b). The highest degradation of HCHO (or formation of CO2(g)) was ~20% (i.e., from 101.5

129

ppm to 78.1 ppm), which was for the 1.5%-Pt/SBT catalyst. Next, the increased catalytical

130

activity was sought by calcinating the 1.5%-Pt/SBT catalyst at 300, 400, and 500 °C,

131

respectively, for 3 h and corresponding prepared catalysts were designated as 1.5%-Pt/SBT-300,

132

1.5%-Pt/SBT-400, and 1.5%-Pt/SBT-500. As shown in Figure 1c, the HCHO concentration onto

133

1.5%-Pt/SBT-400 decreases faster than that onto 1.5%-Pt/SBT-300 and 1.5%-Pt/SBT-500. More

134

than 90 % of HCHO is degraded in 20 min. The simultaneous formation of CO2(g) increases to


Page 6 of 30

Page 7 of 30


135

116.1 ppm onto 1.5%-Pt/SBT-400 (Figure 1d), indicating that the HCHO is completely oxidized

136

to CO2(g) and H2O onto 1.5%-Pt/SBT-400 catalyst at room temperature.

137 138 139 140 141 142 143

Figure 1. Oxidation of HCHO (a, c) and formation of CO2(g) (b, d) using prepared catalysts at room temperature. (a) and (b) Un-calcinated prepared Pt/SBT catalyst of varying weight percent composition of Pt. (c) and (d) Calcinated Pt/SBT containing 1.5% Pt (i.e., 1.5%-Pt/SBT-x where x is temperature of calcination in °C).

144

of HCHO oxidation over 1.5%-Pt/SBT-400 and 1.5%-Pt/SBT (i.e., no calcination) catalysts

145

suggest that catalytic activity of 1.5%-Pt/SBT-400 is ~3.6 times higher than that of 1.5%-Pt/SBT

The role of calcination is further demonstrated in Figure S1. The kinetic linear simulation



146

without calcination. The results of the influence of catalysts in Figure 1 in oxidizing HCHO was

147

understood by subjecting the prepared catalysts to surface analysis.

148

Surface characterization. The XRD patterns of pure SBT, 1.5%-Pt/SBT, 1.5%-Pt/SBT-300,

149

1.5%-Pt/SBT-400, and 1.5%-Pt/SBT-500 are shown in Figure S2. The XRD patterns can be

150

attributed to the pure SBT (JCPDS No. 01-081-0557), which is consistent with a previous

151

study.32 No typical peaks of Pt can be detected for the samples deposited with Pt, suggesting an

152

amorphous state of the Pt NPs in catalysts. Next, phase structure and morphology of catalysts

153

were determined.

154

Figure S3 shows SEM, TEM, and HAADF-STEM images of SBT sample and prepared

155

catalysts. The SBT sample is composed of platelet particles with thicknesses in the range of 60-

156

140 nm (see SEM image of Figure S3a). Low resolution and high resolution TEM images of a

157

single SBT platelet are shown in Figure S4a, b. In case no Pt NPs onto SBT, the distinct (013)

158

lattice fringe with a measured d spacing of 0.46 nm is seen in HRTEM images (Figure S4b),

159

indicating the single crystal nature of the platelets. The corresponding particle size distribution of

160

the Pt0 NPs in 1.5%-Pt/SBT-400 shows that the average particle diameter is ~2 nm (Figure S3c).

161

The TEM images of 1.5%-Pt/SBT-400 (Figure S3b) and 1.5%-Pt/SBT (Figure S5a) suggest the

162

high dispersion of Pt0 NPs. An average particle diameter of the Pt NPs in 1.5%-Pt/SBT is also ~2

163

nm (Figure S5b), indicating that the calcination treatment did not affect the size of the Pt NPs.

164

The dispersion of Pt0 NPs on the SBT platelet was also confirmed by HAADF-STEM images.

165

Figure S3d shows the overall morphology of the 1.5%-Pt/SBT-400 platelet. The whiter

166

spots represent the Pt NPs, which are densely and monodispersely dispersed on the surface of the

167

SBT platelet. The closer observation in Figure S3e indicates that Pt NPs with small average size

168

and narrow size distributions are formed onto the SBT surface. Considering the small specific


Page 8 of 30

Page 9 of 30


169

surface areas of SBT (~2 m2/g), the formation of the uniform dispersion of Pt NPs with such

170

small sizes is possibly related to the ferroelectric property of SBT.32 The corresponding STEM-

171

energy-dispersive X-ray spectrometry (STEM-EDAX) mapping of a single 1.5%-Pt/SBT-400

172

platelet is shown in Figures S3f and S3g, which confirms the homogeneous distribution of Pt

173

over the entire surface of the SBT platelet. The mappings of Sr, Bi, Ta and O elements are

174

presented in Figure S6. Images and particle distributions of other calcinated catalysts (1.5%-

175

Pt/SBT-300 and 1.5%-Pt/SBT-500) were like image of 1.5%-Pt/SBT-400 (Figure S3 and Figure

176

S7). It is therefore concluded that the trend of the oxidation of HCHO by different calcinated

177

1.5%-Pt/SBT-x cannot be described by variation in the morphology of the catalysts. Next,

178

speciation of Pt in Pt/SBT with and without calcination was explored by X-ray photoelectron

179

spectroscopy (XPS) technique.

180 181

XPS measurements. After calcination in air, the proportions of Pt species (or different oxidation

182

states of Pt) in Pt/SBT catalysts may be changed33 and therefore, XPS studies were performed on

183

1.5%-Pt/SBT, 1.5%-Pt/SBT-300, 1.5%-Pt/SBT-400, and 1.5%-Pt/SBT-500 catalysts. The

184

obtained results are shown in Figure 2. As shown in Figure 2a, the Pt 4f core-level XPS spectrum

185

of the 1.5%-Pt/SBT sample can be deconvoluted into three peaks located at 78.0, 74.8, and 72.5

186

eV, which correspond to Pt4+ and Pt0 species in 1.5%-Pt/SBT samples.34−36 This result indicates

187

that originally presented adsorbed Pt4+ species in Pt-SBT samples are not reduced to Pt0 in the

188

photoreduction process.37 Figures 2b, c, and d demonstrate the Pt 4f core-level XPS spectra of

189

the samples calcined at 300, 400, and 500 °C, respectively. As shown in Figure 2b-d, there is a

190

decrease in the Pt0 peaks at approximately 74.2 and 72.1 eV, and a simultaneous emergence of



191

peaks at approximately 75.7 and 72.8 eV, corresponding to Pt2+ species.38,39 This result suggests

192

that Pt2+ species are transformed from Pt0 species during calcination of samples.

193

The variation of platinum species (or contents of Pt0, Pt2+, and Pt4+), obtained from XPS

194

spectra, with temperature in different samples is presented in Figure 2e. The content of Pt4+

195

almost remained unchanged with the heat treatment. However, levels of Pt2+ increase and

196

simultaneous decrease in Pt0 species are seen (Figure 2e). For example, content of Pt2+ gradually

197

increases from undetectable to 49% for the 1.5%-Pt/SBT-500 sample, accompanied by a

198

decrease of Pt0 (from 69% to 21%). Significantly, linear relationships between the contents of Pt0

199

and Pt2+ and temperature are observed (Figure 2e). The formed Pt2+ species is most likely the

200

platinum oxide (PtO), resulted in from the oxidation of Pt0 in calcination of the 1.5%-Pt/SBT

201

sample in air. The formation of Pt-O bond (or PtO) is confirmed by measuring XPS spectra of

202

1.5%-Pt/SBT and 1.5%-Pt/SBT-400 samples (Figure 2f). The shoulder peaks at 529.6 eV can be

203

ascribed to the Pt−O bond,40 which increases significantly after treatment at 400 °C (1.5%-

204

Pt/SBT-400 (calcination) versus 1.5%-Pt/SBT (no calcination)). This indicates the formation of

205

PtO species is from the calcination of the catalyst. The peaks at 532.9 eV and 531.6 eV for both

206

samples are attributed to the dissociated and chemisorbed oxygen species (O2- or O-), OH, or

207

lattice oxygen on the surface of the SBT substrate.41 The XPS results clearly demonstrate the

208

partial conversion of Pt0 to Pt2+ species in calcination. Furthermore, the conversion can be

209

controlled by temperature, giving a new tool to tune the composition of Pt0 and Pt2+ in the

210

Pt/SBT catalysts. Furthermore, the enhanced degradation of HCHO of calcinated 1.5%-Pt/SBT-x

211

compared to un-calcinated 1.5%-Pt/SBT sample (see Figure 1c) may be related to the formation

212

of PtO species in calcination. This is described in next section.


Page 10 of 30

Page 11 of 30


213

214 215 216

Figure 2. (a-d) Pt 4f XPS spectra for 1.5%-Pt/SBT, 1.5%-Pt/SBT-300, 1.5%-Pt/SBT-400, and 1.5%-Pt/SBT-500 samples. (e) The relative intensity changes of Pt0, Pt2+, and Pt4+. (f) O 1s XPS spectra of 1.5%-Pt/SBT and 1.5%-Pt/SBT-400 samples.



217

Tandem catalytic mechanism. The oxidation of HCHO over catalysts was investigated using

218

1.5%-Pt/SBT and 1.5%-Pt/SBT-400 samples. The former sample is un-calcinated catalyst and

219

the later sample corresponds to calcinated catalysts that gives the highest oxidation performance

220

(see Figure 1c). In initial study, oxidation of HCHO was monitored using FT-IR technique,

221

which can observe bands associated with HCHO and its oxidized products. Both catalysts were

222

first exposed to gas mixture of O2, HCHO, H2O, and Ar for 60 min and subsequently to only Ar

223

gas (or purging with Ar gas). Figures 3a and 3b give FT-IR spectra obtained in exposures to

224

1.5%-Pt/SBT-400 and 1.5%-Pt/SBT, respectively. Observed peaks in the spectra after initial 60

225

min exposure are similar for oxidation of HCHO onto both catalysts. However, visible difference

226

in bands is seen when Ar purging is carried out for next 60 min.

227

The band at 1720 cm−1 is assigned to physically adsorbed formic acid (HCOOH) (Figure

228

3).42 Bands at 1610, 1556, and 1450 cm−1 correspond to the vibration of formate species

229

(HCOO−).43-44 The characteristic band of the carbonyl group (C=O, at 1771 cm−1) in HCOO- also

230

appears after exposing catalysts to the gas mixture.45 The spiculate band at 1745 cm−1 belongs to

231

the carbonyl group (C=O) of HCHO,46 which suggests that HCHO molecules are oxidized to

232

HCOO− species over catalysts in the presence of O2 and H2O. The band at 1530 cm−1 can be

233

ascribed to the formation of carbonate species (CO32-),47 indicating that CO32- species are formed

234

and accumulated in the oxidation of HCHO over catalysts. Two bands located at 3850 and 3735

235

cm−1 are assigned to the characteristic vibrations of hydroxyl (OH) groups onto catalysts.48,49

236

When Ar was purged for next 60 min, the peak belonging to CO32- ion at 1530 cm−1

237

disappears in oxidation over 1.5%-Pt/SBT-400 (Figure 3a, red line). Simultaneously, two bands

238

of OH groups, located at 3850 and 3735 cm−1, also disappear after Ar purging (Figure 3a, red

239

line). Comparatively, all these peaks remain when 1.5%-Pt/SBT catalyst is used (Figure 3b, red


Page 12 of 30

Page 13 of 30


240

line). Results of Figure 3 conclude the role of Pt2+ species in oxidation of HCHO because 1.5%-

241

Pt/SBT catalyst is without the Pt2+ species (see Figure 2a and Figure 2e). Furthermore, OH

242

groups of 1.5%-Pt/SBT-400 have a role of the disappearance of CO32- ions.

243

244 245 246 247 248 249 250 251

Figure 3. FT-IR spectra observed during the oxidation of HCHO over catalysts: (a) calcinated sample (1.5%-Pt/SBT-400) and (b) un-calcinated sample (1.5%-Pt/SBT). Black lines are the FTIR spectra of the sample treated in a mixture gas of O2 + HCHO + H2O + Ar for 60 min. Red lines are the FT-IR spectra of the sample treated in a mixture gas of O2 + HCHO + H2O + Ar for 60 min followed by Ar purging for 60 min. Reaction conditions: HCHO (~100 ppm), O2 (20 vol%), H2O (34 vol%), and Ar as the balance.

252

different time intervals of the oxidation of HCHO over both catalysts (Figure 4). Figures 4a and

253

4b show in situ FT-IR spectra obtained at different time during oxidation of HCHO over 1.5%-

254

Pt/SBT-400 and 1.5%-Pt/SBT catalysts exposed to gas mixture of O2, HCHO, H2O, and Ar at

255

room temperature. Characteristics of different peaks correspond to HCOOH, HCOO-, HCHO,

256

CO32-, and OH groups are like bands seen in Figure 3. Attention was paid to evolution of CO32-

257

and OH groups on surfaces of the catalysts. Peak areas of FT-IR peaks at 1530 cm−1 (i.e., CO32-

258

and 3850−3610 cm−1 (i.e., OH groups) as a function time are depicted in Figures 4c and 4d. The

259

concentrations of CO32- and OH onto 1.5%-Pt/SBT-400 attained to a dynamic equilibrium of

The steps of the mechanism were further examined by monitoring of FT-IR peaks at



260

formation and consumption in 10 min of reaction (i.e., no further increase in concentrations of

261

both species with time). Comparatively, levels of CO32- and OH groups on the surface of 1.5%-

262

Pt/SBT increase with the reaction time. The CO32- ions on surfaces poison the activity of catalyst

263

by reducing the number of active sites, hence low oxidation of the HCHO over 1.5%-Pt/SBT is

264

observed (see Figure 1a). It seems that calcinated catalysts, 1.5%-Pt/SBT-400 has desorption

265

mechanism to avoid decrease in active sites to carry oxidation of HCHO (Figure 1c versus

266

Figure 1a). This favorable mechanism to perform oxidation is related to the formation of Pt2+

267

species in calcinated sample (or 1.5%-Pt/SBT-400).

268

269 270 271 272 273 274

Figure 4. In situ FT-IR spectra of (a) 1.5%-Pt/SBT-400 and (b) 1.5%-Pt/SBT in a mixture gas of O2 + HCHO + H2O + Ar at room temperature. The enlarged peaks belonging to OH and CO32are shown on the right sides of Figures 4a and b. (c, d) Areas of the dominant peak belonging to the CO32- (at 1530 cm−1) and a series of dense peaks belonging to OH (ranging from 3850 cm−1 to 3610 cm−1) versus time during reaction in an O2 + HCHO + H2O + Ar gas mixture. Reaction conditions: HCHO (~100 ppm), O2 (20 vol%), H2O (34 vol%), and Ar as the balance. 14 Environment ACS Paragon Plus

Page 14 of 30

Page 15 of 30


275 276

The role of O2 in the catalytic mechanism was explored by eliminating O2 from the gas

277

mixture. Results of collected in situ FT-IR spectra after exposing the gas mixture of H2O, HCHO,

278

and Ar to 1.5%-Pt/SBT-400 and 1.5%-Pt/SBT catalysts are shown in Figure S8. After 20 min

279

exposure, no peaks of OH, HCOO−, and CO32- are observed, implying O2 is a critical component

280

of gas mixture to oxidize HCHO by both catalysts.

281

Next, participation of water in the steps of mechanism was investigated by exposing gas

282

mixture of O2, HCHO, and Ar (i.e., no H2O) to 1.5%-Pt/SBT-400 catalyst and the degradation of

283

HCHO and the formation of CO2(g) (Figure 5). Without H2O, the degradation of HCHO is

284

slower than with H2O in gas mixture (Figure 5a). This suggests that water in gas mixture

285

facilitates the activity of catalyst better than no water involved in the oxidation of HCHO.

286

Formed CO32- ions in the oxidation of HCHO likely adsorb on the catalyst to poison the activity

287

of 1.5%-Pt/SBT-400. However, this poisoning of the catalyst is diminished by water via the

288

formation of OH groups at the catalyst surface, which ultimately converts CO32- ions to CO2(g).

289

Formation of CO2(g) was monitored during the degradation of HCHO. As shown in Figure 5b,

290

H2O was able to stoichiometrically convert HCHO to CO2(g). Comparatively, the oxidation of

291

HCHO without H2O results in smaller amount of CO2(g) than that of expected concentration

292

from the conversion of HCHO in oxidation over 1.5%-Pt/SBT-400 catalyst. This further implies

293

H2O is participating in oxidation by not allowing CO32- ion to interfere in the activity of the

294

prepared calcinated catalyst (i.e., 1.5%-Pt/SBT-400) by completing the oxidation process to

295

convert HCHO to CO2(g).



296

297 298 299 300 301

Figure 5. Degradation of HCHO and formation of CO2(g) with and without H2O using the 1.5%Pt/SBT-400 catalyst: (a) HCHO and (b) CO2(g) (Reaction conditions: HCHO (~100 ppm), O2 (20 vol%), H2O (34 vol%), temperature (25 °C), and Ar as the balance).

302

Results of Figures 3-5 demonstrate the operation of tandem catalytical mechanism in the

303

oxidation of HCHO to CO2(g) by prepared catalyst, 1.5%-Pt/SBT-400 in our study. The

304

mechanism is schematically presented in Figure 6. Initially, HCHO is adsorbed onto the surface

305

of 1.5%-Pt/SBT catalyst (or on Pt0 NPs), possible via hydrogen bonding.50 Molecules of O2 are

306

also simultaneously adsorb onto Pt0 NPs and decompose into active oxygen radicals (O-). The

307

activated oxygen species oxidize HCHO to formate (HCOO-) ions. The HCOO- ions are also

308

oxidized by activated oxygen species to yield CO32- ions. Both prepared un-calcinated catalyst

309

(1.5%-Pt/SBT) and calcinated catalyst (1.5%-Pt/SBT-400) have same steps of oxidizing HCHO

310

to CO32- through intermediate HCOO- ions (Figures 6a, b). The similarity of the steps was

311

explored by conducting catalytic oxidation of HCHO using both catalysts at different

312

temperature. The rate constants (k) of the degradation of HCHO at different temperature were

313

determined. The plots of lnk versus 1/T(K) give apparent activation energies (Figure S9), which


Page 16 of 30

Page 17 of 30


314

are 10.45 ± 0.81 kJ/mol and 11.09 ± 0.47 kJ/mol for degradation of HCHO by applying 1.5%-Pt-

315

SBT-400 and 1.5%-Pt-SBT, respectively. Similar values of apparent activation energy suggest

316

that the similar step may be involved in mechanism of the oxidation of HCHO in using both

317

catalysts. However, the active site of Pt0 to participate in oxidation of HCHO likely poisoned by

318

CO32- (or decrease in number of active sites) in using 1.5%-Pt-SBT to decrease the overall

319

oxidation rate. Significantly, the presence of Pt2+ (or PtO) species in 1.5%-Pt-SBT/400 can

320

convert poisoned adsorbed CO32- ions to CO2(g) (or desorption of CO32- ions) to diminish

321

poisoning of the catalyst. This conversion step may be presented by reactions (1) and (2). These

322

reactions are not possible in applying un-calcinated 1.5%-Pt-SBT catalyst to oxidize HCHO.

323 324

It has been reported that oxygen atoms on the PtO surface can abstract hydrogen from water to create OH groups:28

325

2PtO + H2O →Pt2+-OH + Pt2+-O-OH

(1)

326

2Pt2+-OH + Pt0-CO3 → 2PtO + Pt0 + CO2(g) + H2O

(2)

327

In presence of H2O, formation of Pt2+-OH and Pt2+-O-OH species onto 1.5%-Pt/SBT-400 occur

328

(reaction 1).51 The Pt2+-OH species may supply protons, either directly or indirectly.52,53 Protons

329

on surfaces are able to convert adsorbed CO32- ions to CO2(g) (reaction 2). The formed Pt2+-O-

330

OH species may also be involved in oxidation of HCHO by reacting with an intermediate,

331

HCOO- species to directly produce CO2(g).51 Overall, an active site directed tandem catalysis

332

mechanism of 1.5%-Pt/SBT-400 is operational. However, the 1.5%-Pt/SBT catalyst is not able to

333

carry out reactions (1) and (2) because of absence of Pt2+ species (see Figures 2a and 2e).

334

Therefore, CO32- ions onto 1.5%-Pt/SBT surfaces cannot be desorb (or no tandem catalytic

335

activity) and poisoning of the catalyst happens to decrease the activity to oxidize HCHO (see

336

Figure 1).



337

The role of Pt2+ species in tandem catalytic mechanism of 1.5%-Pt-SBT-400 is also

338

supported indirectly by the oxidation of HCHO by Pt/TiO2 catalyst under same conditions. The

339

Pt/TiO2 catalyst was prepared using a previous report (Text S3).54 The Pt/TiO2 catalyst is without

340

Pt2+ species while the tandem catalyst, 1.5%-Pt-SBT-400, contains Pt2+ species. When exposing

341

gas mixture of O2, HCHO, H2O, and Ar to Pt/TiO2 catalyst, the degradation of HCHO takes

342

place (Figure S10). However, the oxidation was incomplete in 20 min (101.2 ppm to 47.5 ppm).

343

Also, the activity of Pt/TiO2 catalyst appears to be almost stopped at ~10 min. Furthermore,

344

degraded HCHO does not correspond to equal amount of the formation of CO2(g) (Figure S10).

345

This suggests the deficiency in the Pt/TiO2 catalyst, which could be overcome in the

346

development of a tandem catalyst, 1.5%-Pt/SBT-400 in our study (see Figure 1c).

347

Significantly, 1.5%-Pt/SBT-400 had high catalytical activity than that the observed

348

activity using 1.5%-Pt/SBT-300 and 1.5%-Pt/SBT-500 catalysts (see Figure 1c). This may be

349

understood by considering the cooperative effect between Pt0 and Pt2+ species in the tandem

350

catalysis process during the oxidation of HCHO. The increase of Pt2+ due to increase in

351

temperature of calcination inevitably causes the decrease of Pt0 (see Figure 2e), which decreases

352

active sites for activating O2 in the first step of oxidation of HCHO to from CO32- ions. After

353

introducing the Pt2+ species into calcinated Pt/SBT at different temperatures, the

354

synergistic effect between Pt0 and Pt2+ occurs during the degradation of HCHO to CO2(g). It

355

appears that the optimum levels of both Pt0 and Pt2+ exist in 1.5%-Pt/SBT-400 to yield higher

356

catalytic activity than the activity generated by 1.5%-Pt/SBT-300 and 1.5%-Pt/SBT-500.


Page 18 of 30

Page 19 of 30


357 358 359 360

Figure 6. Plausible reaction pathway for oxidation of HCHO over (a) 1.5%-Pt/SBT catalyst, and (b) 1.5%-Pt/SBT-400 catalyst at room temperature.

361

Significance. The newly developed tandem catalyst in our study has demonstrated high

362

effectiveness to fully degrade HCHO to CO2(g) at room temperature. The 1.5%-Pt/SBT-400

363

catalyst exhibits favorable ability to oxidize HCHO completely for six cycling tests (Figure 7a).

364

No obvious decline in HCHO oxidation occurs after six cycling tests; indicating high stability of

365

the 1.5%-Pt/SBT-400 catalyst. The suitability of the 1.5%-Pt/SBT-400 catalyst was also tested in

366

continuous oxidation process. The continuous oxidation of HCHO over 1.5%-Pt/SBT-400

367

catalyst (0.3 g) was carried out in a fixed bed reactor system. Online Photoacoustic IR Multigas

368

Monitor was connected to a tail gas collector to determine the concentration of HCHO. The

369

standard HCHO feed gas contains ~100 ppm of HCHO, 20% O2, 34% H2O, and Ar (as the

370

balance). The concentration of HCHO in the feed gas was adjusted by changing the flow rate of

371

Ar using a rotameter. The total flow rate was approximately 40 mL min−1, corresponding to a gas

372

hourly space velocity (GHSV) of 12600 h−1. As shown in Figure 7b, ~5% activity loss was lost

373

in 200 min. The oxidation activity of 1.5%-Pt/SBT-400 was maintained to ~90% HCHO 19 Environment ACS Paragon Plus


374

conversion. This supports the reasonably high stability of the 1.5%-Pt/SBT-400 catalyst under

375

continuous oxidation of HCHO. Comparatively, 1.5%-Pt/SBT catalyst, which does not carry

376

tandem catalytical activity, oxidation of HCHO was completely inhibited in 40 min (Figure 7c).

377

This suggests that complete deactivation of 1.5%-Pt/SBT catalyst in a short period of time and

378

this catalyst is not appropriate to carry oxidation of HCHO. Overall, high effectiveness of the

379

tandem catalyst of our study may be applicable to oxidize other organic compounds.


Page 20 of 30

Page 21 of 30


380 381 382 383

Figure 7. Durability test of HCHO oxidation over 1.5%-Pt/SBT-400 and 1.5%-Pt/SBT catalysts: (a) cycling test for 1.5%-Pt/SBT-400, (b) continuous test for 1.5%-Pt/SBT-400, and (c) continuous test for 1.5%-Pt/SBT.



384

ASSOCIATED CONTENT

385

Supporting Information

386

Synthesis of SrBi2Ta2O9 (Text S1), loading of the Pt nanoparticles (Text S2), preparation of

387

Pt/TiO2 catalyst (Text S3), kinetic linear simulation for HCHO oxidation (Figure S1), XRD

388

patterns (Figure S2), SEM, TEM, and HAADF-STEM images (Figures S3-S7), in situ FT-IR

389

spectra in gas mixture of HCHO, H2O, and Ar (Figure S8), Plots of lnk versus 1/T(K) for the

390

oxidation of HCHO (Figure S9), and the HCHO oxidation performance over Pt/TiO2 catalyst

391

(Figure S10) (PDF)

392

AUTHOR INFORMATION

393

Corresponding Authors

394

*Emails: [email protected] and [email protected]

395 396

Notes

397

The authors declare no competing financial interest.

398

ACKNOWLEDGMENT

399

This work was supported by the National Natural Science Foundation of China (Grant Nos.

400

21643012 and U1403193). We thank anonymous reviewers for their comments, which improved

401

the paper greatly.

402 403 404 405


Page 22 of 30

Page 23 of 30


406

REFERENCES

407

(1) Zhang, L.; Routsong, R.; Strand, S. E. Greatly enhanced removal of volatile organic

408

carcinogens by a genetically modified houseplant, pothos Ivy (epipremnum aureum) expressing

409

the mammalian cytochrome P450 2e1 gene. Environ. Sci. Technol. 2019, 53 (1), 325–331.

410

(2) Zhu, M.; Muhammad, Y.; Hu, P.; Wang, B.; Wu, Y.; Sun, X.; Tong, Z.; Zhao, Z. Enhanced

411

interfacial contact of dopamine bridged melamine-graphene/TiO2 nano-capsules for efficient

412

photocatalytic degradation of gaseous formaldehyde. Appl. Catal. B 2018, 232, 182–193.

413

(3) Chen, X.; Gao, P.; Guo, L.; Wen, Y.; Fang, D.; Gong, B.; Zhang, Y.; Zhang, S. High-

414

efficient physical adsorption and detection of formaldehyde using Sc-and Ti-decorated

415

graphdiyne. Phys. Lett., A 2017, 381 (9), 879–885.

416

(4) Sun, X.; Lin, J.; Guan, H.; Li, L.; Sun, L.; Wang, Y.; Miao, S.; Su, Y.; Wang, X. Complete

417

oxidation of formaldehyde over TiO2 supported subnanometer Rh catalyst at ambient

418

temperature. Appl. Catal., B 2018, 226, 575–584.

419

(5) Xu, Z.; Yu, J.; Xiao, W. Microemulsion-assisted preparation of a mesoporous

420

ferrihydrite/SiO2 composite for the efficient removal of formaldehyde from air. Chem.-Eur. J.

421

2013, 19 (29), 9592–9598.

422

(6) Zhu, X.; Gao, X.; Qin, R.; Zeng, Y.; Qu, R.; Zheng, C.; Tu, X. Plasma-catalytic removal of

423

formaldehyde over Cu–Ce catalysts in a dielectric barrier discharge reactor. Appl. Catal., B 2015,

424

170, 293–300.

425

(7) Lin, M.; Yu, X.; Yang, X.; Li, K.; Ge, M.; Li, J. Highly active and stable interface derived

426

from Pt supported on Ni/Fe layered double oxides for HCHO oxidation. Catal. Sci. Technil.

427

2017, 7 (7), 1573–1580.



428

(8) Yu, L.; Peng, R.; Chen, L.; Fu, M.; Wu, J.; Ye, D. Ag supported on CeO2 with different

429

morphologies for the catalytic oxidation of HCHO. Chem. Eng. J. 2018, 334, 2480–2487.

430

(9) Xu, Q.; Lei, W.; Li, X.; Qi, X.; Yu, J.; Liu, G.; Wang, J.; Zhang, P. Efficient removal of

431

formaldehyde by nanosized gold on well-defined CeO2 nanorods at room temperature. Environ.

432

Sci. Technol. 2014, 48 (16), 9702–9708.

433

(10) Nie, L.; Meng, A.; Yu, J.; Jaroniec, M. Hierarchically macro-mesoporous Pt/γ-Al2O3

434

composite microspheres for efficient formaldehyde oxidation at room temperature. Sci. Rep.

435

2013, 3, 3215.

436

(11) Ma, L.; Wang, D.; Li, J.; Bai, B.; Fu, L.; Li, Y. Ag/CeO2 nanospheres: Efficient catalysts for

437

formaldehyde oxidation. Appl. Catal., B 2014, 148, 36–43.

438

(12) Xu, Z.; Yu, J.; Jaroniec, M. Efficient catalytic removal of formaldehyde at room

439

temperature using AlOOH nanoflakes with deposited Pt. Appl. Catal., B 2015, 163, 306–312.

440

(13) Chen, H.; Rui, Z.; Ji, H. Titania-supported Pt catalyst reduced with HCHO for HCHO

441

oxidation under mild conditions. Chin. J. Catal. 2015, 36 (2), 188–196.

442

(14) Lv, T.; Peng, C.; Zhu, H.; Xiao, W. Heterostructured Fe2O3@SnO2 core–shell nanospindles

443

for enhanced Room-temperature HCHO oxidation. Appl. Surf. Sci. 2018, 457, 83–92.

444

(15) Cui, W.; Xue, D.; Tan, N.; Zheng, B.; Jia, M.; Zhang, W. Pt supported on octahedral Fe3O4

445

microcrystals as a catalyst for removal of formaldehyde under ambient conditions. Chin. J. Catal.

446

2018, 39(9), 1534–1542.

447

(16) Wong, A.; Liu, Q.; Griffin, S.; Nicholls, A.; Regalbuto1, J. R. Synthesis of ultrasmall,

448

homogeneously alloyed, bimetallic nanoparticles on silica supports. Science. 2017, 358 (6369),

449

1427–1430.


Page 24 of 30

Page 25 of 30


450

(17) Kalinin, S. V.; Bonnell, D. A.; Alvarez, T.; Lei, X.; Hu, Z.; Ferris, J. H. Atomic polarization

451

and local reactivity on ferroelectric surfaces: A new route toward complex nanostructures. Nano.

452

Lett. 2002, 2 (6), 589–593.

453

(18) Li, L.; Gao, P.; Nelson, C. T.; Jokisaari, J.; Zhang, Y.; Kim, S. J.; Melville, K.; Adamo, C.;

454

Schlom, D. J.; Pan, X. Atomic scale structure changes induced by charged domain walls in

455

ferroelectric materials. Nano. Lett. 2013, 13 (11), 5218–5223.

456

(19) Dunn, S.; Jones, P. M.; Gallardo, D. E. Photochemical growth of silver nanoparticles on c-

457

and c+ domains on lead zirconate titanate thin films. J. Am. Chem. Soc. 2007, 129 (28), 8724.

458

(20) Polking, M. J.; Zheng, H.; Ramesh, R.; Alivisatos, A. P. Controlled synthesis and size-

459

dependent polarization domain structure of colloidal germanium telluride nanocrystals. J. Am.

460

Chem. Soc. 2011, 133 (7), 2044–2047.

461

(21) Liang, S. J.; Zhu, S. Y.; Zhu, J.; Chen, Y.; Zhang, Y. F.; Wu, L. The effect of group IIIA

462

metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6· H2O. Phys.

463

Chem. Chem. Phys. 2012, 14 (3), 1212–1222.

464

(22) Liang, S. J.; Shen, L. J.; Zhu, J.; Zhang, Y. F.; Wang, X. X.;

465

Morphology-controlled synthesis and efficient photocatalytic performances of a new promising

466

photocatalyst Sr0.25H1.5Ta2O6·H2O. Rsc Adv. 2011, 1 (3), 458-467.

467

(23) Liang, S. J.; Wang, X. W.; Chen, Y.; Zhu, J.; Zhang, Y. F.; Wang, X. X.; Li, Z. H.; Wu, L.

468

Sr0.4H1.2Nb2O6·H2O nanopolyhedra: An efficient photocatalyst. Nanoscale 2010, 2 (10), 2262–

469

2268.

470

(24) Liang, S. J.; Wu, L.; Bi, J. H.; Wang, W. J.; Gao, J. A.; Li, Z. H.; Fu, X. Z. A novel

471

solution-phase approach to nanocrystalline niobates: selective syntheses of Sr0.4H1.2Nb2O6·H2O


Li, Z. H.; Wu, L.; Fu, X. Z.


472

nanopolyhedrons and SrNb2O6 nanorods photocatalysts. Chem. Commun. 2010, 46 (9), 1446–

473

1448.

474

(25) Wu, W.; Liang, S.; Wang, X.; Bi, J.; Liu, P.; Wu, L. Synthesis, structures and photocatalytic

475

activities of microcrystalline ABi2Nb2O9 (A= Sr, Ba) powders. J. Solid State Chem., 2011, 184

476

(1), 81–88.

477

(26) Wu, W.; Liang, S.; Chen, Y.; Shen, L.; Zheng, H.; Wu, L. High efficient photocatalytic

478

reduction of 4-nitroaniline to p-phenylenediamine over microcrystalline SrBi2Nb2O9. Catal.

479

Commun. 2012, 17, 39–42.

480

(27) Ke, J.; Zhu, W.; Jiang, Y.; Rui, S. Strong local coordination structure effects on

481

subnanometer PtOx clusters over CeO2 nanowires probed by low-temperature CO Oxidation.

482

ACS Catal. 2015, 5 (9), 5164–5173.

483

(28) Li, Y. H.; Xing, J.; Chen, Z. J.; Li, Z.; Tian, F.; Zheng, L. R.; Wang, H. F.; Hu, P.; Zhao, H.

484

J.; Yang, H. G. Unidirectional suppression of hydrogen oxidation on oxidized platinum clusters.

485

Nat. Commun. 2013, 4, 2500.

486

(29) Wasilke, J. C.; Obrey, S. J.; Baker, R. T.; Bazan, G. C. Concurrent tandem catalysis. Chem.

487

Rev. 2005, 105 (3), 1001–1020.

488

(30) Yamada, Y.; Tsung, C. K.; Huang, W. Nanocrystal bilayer for tandem catalysis. Nat. Chem.

489

2011, 3 (5), 372−376.

490

(31) Li, X.; Guo, Z.; Xiao, C.; Goh, T. W.; Tesfagaber, D.; Huang, W. Tandem catalysis by

491

palladium nanoclusters encapsulated in metal–organic frameworks. ACS Catal. 2014, 4 (10),

492

3490−3497.

493

(32) Li, Y.; Zang, L.; Li, Y.; Liu, C.; Zhang, Y.; He, H. Photoinduced topotactic growth of

494

bismuth nanoparticles from bulk SrBi2Ta2O9. Chem. Mater. 2013, 25 (10), 2045–2050.


Page 26 of 30

Page 27 of 30


495

(33) An, N.; Yu, Q.; Liu, G.; Li, S.; Jia, M.; Zhang, W. Complete oxidation of formaldehyde at

496

ambient temperature over supported Pt/Fe2O3 catalysts prepared by colloid-deposition method. J.

497

Hazard. Mater. 2011, 186 (2), 1392–1397.

498

(34) Pretzer, L. A.; Carlson, P. J.; Boyd, J. E. The effect of Pt oxidation state and concentration

499

on the photocatalytic removal of aqueous ammonia with Pt-modified titania. J. Photochem.

500

Photobiol. A: Chem. 2008, 200 (2), 246–253.

501

(35) Zhang, S.; Shao, Y.; Yin, G.; Lin, Y. Carbon nanotubes decorated with Pt nanoparticles via

502

electrostatic self-assembly: A highly active oxygen reduction electrocatalys. J. Mater. Chem.

503

2010, 20 (14), 2826–2830.

504

(36) Joseph, T.; Kumar, K. V.; Ramaswamy, A. V.; Halligudi, S. B. Au–Pt nanoparticles in

505

amine functionalized MCM-41: Catalytic evaluation in hydrogenation reactions. Catal. Commun.

506

2007, 8 (3), 629–634.

507

(37) Dong, C.; Lian, C.; Hu, S.; Deng, Z.; Gong, J.; Li, M.; Liu, H.; Xing, M.; Zhang, J. Size-

508

dependent activity and selectivity of carbon dioxide photocatalytic reduction over platinum

509

nanoparticles. Nat. Commun. 2018, 9 (1), 1252.

510

(38) Bera, P.; Patil, K. C.; Jayaram, V.; Subbanna, G. N.; Hegde, M. S. Ionic dispersion of Pt and

511

Pd on CeO2 by combustion method: Effect of metal–ceria interaction on catalytic activities for

512

NO reduction and CO and hydrocarbon oxidation. J. Catal. 2000, 196 (2), 293–301.

513

(39) Zhou, Y.; Menendez, C. L.; Guinel, M. J.-F.; Needels, E. C.; Gonzalez-Gonzalez, I.;

514

Jackson, D. L.; Lawrence, N. J.; Cabrera, C. R.; Cheung, C. L. Influence of nanostructured ceria

515

support on platinum nanoparticles for methanol electrooxidation in alkaline media. RSC Adv.

516

2014, 4 (3), 1270−1275.



517

(40) Arrigo, R.; Hävecker, M.; Schuster, M. E.; Ranjan, C.; Stotz, E.; Knop-Gericke, A.; Schlögl,

518

R. In situ study of the gas-phase electrolysis of water on platinum by NAP–XPS. Angew. Chem.,

519

Int. Ed. 2013, 52 (44), 11660–11664.

520

(41) Wang, Y.; Lü, Y.; Zhan, W.; Xie, Z.; Kuang, Q.; Zheng, L. Synthesis of porous Cu2O/CuO

521

cages using Cu-based metal-organic frameworks as templates and their gas-sensing properties. J.

522

Mater. Chem. A 2015, 3 (24), 12796–12803.

523

(42) Samjeské, G.; Osawa, M. Current oscillations during formic acid oxidation on a Pt electrode:

524

Insight into the mechanism by time-resolved IR spectroscopy. Angew. Chem., Int. Edit. 2005, 44

525

(35), 5694–5698.

526

(43) Yan, Z.; X, Z.; Yu, J.; Jaroniec, M. Highly active mesoporous ferrihydrite supported Pt

527

catalyst for formaldehyde removal at room temperature. Environ. Sci. Technol. 2015, 49 (11),

528

6637–6644.

529

(44) Kecskés, T.; Raskó, J.; Kiss, J. FTIR and mass spectrometric studies on the interaction of

530

formaldehyde with TiO2 supported Pt and Au catalysts. Appl. Catal., A 2004, 273 (1), 55–62.

531

(45) Liu, F.; Shen, J.; Xu, D.; zhou, W.; Zhang, S.; Wan, L. Oxygen vacancies enhanced HCHO

532

oxidation on a novel NaInO2 supported Pt catalyst at room temperature. Chem. Eng. J. 2018, 334,

533

2283–2292.

534

(46) Kumar, D.; Varma, S.; Kamble, V. S.; Gupta, N. M. The selective adsorption/reaction of

535

methanol over nanosize uranium oxide crystallites dispersed in MCM-48: FT-IR and TPD

536

studies. J. Mol. Catal. A: Chem. 2004, 223 (1), 251–257.

537

(47) Gutiérrez-Arzaluz, M.; Torres-Rodríguez, M.; Mugica-Alvarez, V. Wet oxidation of

538

formaldehyde with heterogeneous catalytic materials. Int. J. Environ. Sci. Dev. 2016, 7 (3), 166.


Page 28 of 30

Page 29 of 30


539

(48) Rong, S.; Zhang, P.; Yang, Y., Zhu, L.; Wang, J.; Liu, F. MnO2 Framework for

540

Instantaneous Mineralization of Carcinogenic Airborne Formaldehyde at Room Temperature.

541

ACS Catal. 2017, 7 (2), 1057–1067.

542

(49) Zhu, X.; Yu, J.; Jiang, C.; Cheng, B. Catalytic decomposition and mechanism of

543

formaldehyde over Pt–Al2O3 molecular sieves at room temperature. Phys. Chem. Chem. Phys.

544

2017, 19 (10), 6957–6963.

545

(50) Xu, Z.; Yu, J.; Liu, G.; Cheng, B.; Zhou, B.; Li, X. Microemulsion-assisted synthesis of

546

hierarchical porous Ni(OH)2/SiO2 composites toward efficient removal of formaldehyde in air.

547

Dalton. Trans. 2013, 42 (28), 10190–10197.

548

(51) Zhang, C.; Liu, F.; Zhai, Y.; Yi, N.; Liu, Asakura, Y. K.; Flytzani-Stephanopoulos, M.; He,

549

H. Alkali-metal-promoted Pt/TiO2 opens a more efficient pathway to formaldehyde oxidation at

550

ambient temperatures. Angew. Chem., Int. Ed. 2012, 51 (38), 9628–9632.

551

(52) Onishi, T.; Abe, H.; Maruya, K.; Domen, K. Ir spectra of hydrogen adsorbed on ZrO2. J.

552

Chem. Soc. Chem. Commun. 1985, (9), 617–618.

553

(53) Kondo, J.; Domen, K.; Maruya, K.; Onishi, T. Infrared study of molecularly adsorbed H2 on

554

ZrO2. Chem. Phys. Lett. 1992, 188 (5), 443–445.

555

(54) Nie, L.; Yu, J.; Li, X.; Cheng, B.; Liu, G.; Jaroniec, M. Enhanced performance of NaOH-

556

modified Pt/TiO2 toward room temperature selective oxidation of formaldehyde. Environ. Sci.

557

Technol. 2013, 47, 2777−2783.

558 559 560 561



562

TOC

563 564


Page 30 of 30

Active Site-Directed Tandem Catalysis on Single Platinum

Recommend Documents