Flexible Pt-Promoted Graphene Aerogel Monolith: A Versatile Catalyst

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Materials and Interfaces

Flexible Pt-Promoted Graphene Aerogel Monolith: A Versatile Catalyst for Room-Temperature Removal of Carbon Monoxide, Formaldehyde and Ethylene Xinnan Jiang, Weiyi Yao, Jitong Wang, Licheng Ling, and Wenming Qiao Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b03800 • Publication Date (Web): 05 Oct 2018 Downloaded from http://pubs.acs.org on October 15, 2018

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Flexible Pt-Promoted Graphene Aerogel Monolith: A Versatile Catalyst for RoomTemperature Removal of Carbon Monoxide, Formaldehyde and Ethylene Xinnan Jianga, Weiyi Yaoa, Jitong Wang*ab, Licheng Lingab, Wenming Qiao*ab a

State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China

b

Key Laboratory of Specially Functional Polymeric Materials and Related Technology of the

Ministry of Education (East China University of Science and Technology), Shanghai, China Corresponding Author:

Jitong Wang, E-mail: [email protected] Wenming Qiao, E-mail: [email protected]

Abstract: Three-dimensional flexible Pt-promoted graphene aerogel monolith is developed through a one-step solvothermal process as a versatile catalyst for removal of CO, HCHO and C2H4 at room-temperature. In this synthesis, ethylene glycol was employed as both reducing agent and the solvent which could accelerate the in-situ reduction of GO and metal ions during the solvothermal process, leading to the assembly and crosslinking of GO to form a 3D network. Therefore, the obtained Pt-promoted graphene aerogel monolith exhibits an interconnected, honeycomb-like 3D porous framework with highly dispersed Pt (0) species, making it ideal for catalytic oxidation. Such monolith shows a high performance for the catalytic oxidation of CO, HCHO and C2H4, with 100% conversion at room temperature, with an excellent stability longer than 72 h. These results demonstrate that the flexible Pt-promoted graphene aerogel monolith gives significance on catalytic oxidation, which could be applied in eliminating indoor air pollution.

Keywords: Platinum; Graphene oxide aerogel monolith; Catalytic oxidation; Carbon monoxide; Formaldehyde; Ethylene


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1. INTRODUCTION Indoor air pollution (IAP) is a leading risk factor for global disease burden since people spend the greater part of their daily lives indoors. Together with fine particles, gases (such as nitrogen dioxide, carbon monoxide, sulphur dioxide and ozone), and volatile organic compounds (VOC), the easiest access of indoor air pollutants was supposed to be second-hand smoke. As one kind of gas without any colour and odour, carbon monoxide (CO) is derived from incomplete combustion of organic material from space heaters, defective central heating furnaces and environmental tobacco smoke1, being the main reason of air pollution in the world. Formaldehyde (HCHO) is one of the most problematic volatile organic compounds emitted from indoor decorating materials including plywood, particleboard, and fiberboard2 that could cause health problems such as nasal tumours and skin irritation after a long-term exposure3. In addition, ethylene (C2H4) is one kind of plant hormone produced by fruit, vegetable, environmental tobacco smoke and wood or propane fuel use, causing physicochemical changes of climacteric plants4 that accelerate the quality loss or even metamorphism of fruits and vegetables 5, 6. Therefore, elimination of the indoor pollutant gases is necessary for good indoor air quality. The elimination methods of indoor pollutant gases mainly include adsorption and catalytic oxidation. In adsorption process, adsorbents such as activated carbon, zeolite and active alumina, have popular applications in air pollution treatment7-9. However, because of either the ion-quadrupole interaction10 or Van der Waals force, most of these adsorbents may reversibly trap these pollutant gases, leading to a very low adsorption selectivity, especially for the pollutant gases with very trace concentration. Catalytic oxidation, in which solid catalysts constituted by porous support with high specific surface area and active phase (noble metals or some transition-metal oxides provide active phases) are usually employed, has already been well investigated as an effective and facile technology for complete removal of CO11, HCHO12 and C2H413. Catalytic oxidation exhibits a series of critical potential advantages for the removal of indoor pollutant gases, including stability, high performance, high selectivity and nontoxicity. Generally, both transition metal oxides and supported noble metals could be employed as catalysts for oxidation of pollutant gases. Among the various transition metal oxide catalysts, hopcalite catalyst (consists of copper and manganese oxides) has been wildly used as an efficient catalyst for the removal of CO, HCHO and C2H414-16. The excellent activity of MnO2CuO mixed oxides originate from the high adsorption capacity of gaseous reactant molecules



and Cu2+Mn3+/Cu+Mn4+ redox process17. However, hopcalite catalyst could only show its catalytic ability at a relative high temperature, while displays no activity at ambient temperature18-20. Other transition-metal oxides, for example, some of the cobalt oxide catalysts (CoOx, usually as Co3O4 or CoO), could be used for CO removal at -77 oC21 and C2H4 oxidization at 0 oC22. However, they show no activity for HCHO oxidation at room temperature. In order to achieve the simultaneous removal of CO, HCHO and C2H4, supported noble metal catalyst had to be took into consideration. Noble metals, such as Pt, Pd and Au, are usually considered as highly active catalysts for catalytic oxidization of CO, HCHO and volatile organic compounds (VOC) in low temperature. Up to our knowledge, Pt-based catalysts are believed to be the most efficient catalysts for catalytic oxidation due to their abundant active sites and long lifespan. Many reported Pt-based catalysts show exceptional activity for CO oxidation at room temperature, and some of them could be used for HCHO removal at a very low temperature23-25. However, to our best knowledge, Pt-based catalysts with excellent room temperature catalytic performance for the simultaneous removal of CO, HCHO and C2H4 have never been reported. Besides, the support of the noble metal is usually metal oxide or carbon materials, most of which are always prepared into powder or irregular shapes with poor mechanical properties, limiting the application of these catalysts in heterogeneous reaction. In the present study, we presented a flexible 3D Pt nanoparticle-promoted graphene aerogel (Pt-GA) catalyst with excellent mechanical properties including low density, high strength and excellent flexibility, which could achieve complete elimination of CO, HCHO and C2H4 at room temperature (20 oC). The preparation strategy of the catalyst is the widely applied polyolmediated solvothermal method, in which ethylene glycol (EG) is used as both solvent and reducing agent for Pt nanoparticle formation26. The in-situ chemical and hydrothermal reduction of between graphene oxide sheets and metal ions could be efficiently promoted by EG which possess both a high boiling point and a high viscosity. In addition, the linking between graphene and nanoparticles could be more efficient with the help of the oxygencontaining functional groups provided by GO27, leading to the uniform distribution of Pt nanoparticles. Through the self-assembly reduction of graphene oxide (GO), 3D composite architecture could be obtained, meantime, metallic Pt nanoparticles decorated onto the GO sheets with high dispersion28. The large surface area and the open macropore structure of graphene aerogel monolith enable the accessibility of nanoparticles and provided pathways for inner and outer diffusion of reaction gases29. Due to the unique structure and chemical properties, Pt-GA demonstrates an outstanding and universal catalytic activity for the indoor pollutant gases, exhibiting a 100% conversion for CO, HCHO and C2H4 at 25 °C and excellent


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catalytic stability and life span, much higher than common commercial Pt/carbon catalyst (PtC). This polyol-mediated solvothermal method is a promising approach for synthesis of carbonbased catalysts, and also could be promising in the development of wide-ranged composite carbon materials for advanced applications.

2. EXPERIMENTAL SECTION 2.1. Preparation of Catalyst. Graphite oxide (GO) was prepared by the Hummers method and dispersed in ethylene glycol to obtain a pristine graphene suspension with a final concentration of 2 mg/mL. In a typical process, 500 μL of platinum chloride (0.1 mol/L) aqueous solution was added to 50 mL of the graphene suspension. After stirred for 3 h, the mixture was transferred into a Telfon-lined autoclave and hydrothermally treated at 180 oC for 24 h. The obtained aerogel monolith was washed with de-ion water to replace the ethylene glycol with water and then freezing dried.

2.2. Characterization of Catalyst.

The morphological images of the samples were observed under scanning electron microscopy (SEM, JEOL 7100F) and transmission electron microscopy (TEM, JEOL 2100F). Thermo-gravimetric analysis (TGA) results was obtained by a TA Instruments Q600 thermogravimetric analyser, ramping temperature to 800 oC at a rate of 5 oC/min, in an air flow of 100 mL/min. The weight of Pt loaded on GA was calculated according to ash content after calcination.

Porosity

structure

was

analysed

through

low-temperature

nitrogen

adsorption/desorption isotherms (at 77 K) which was obtained by an ASAP 2020 instrument (Micromeritics). Before the process, the samples were under degassing treatment in vacuum at 120 °C for 12 h. The specific surface area was calculated according to the Brunauer-EmmettTeller (BET) equation, and pore size distribution was derived from the density function thoery (DFT) method. The X-ray diffraction (XRD) patterns were achieved on a Rigaku D/max 2550 diffractometer at 40 kV and 20 mA using Cu Kα radiation (0.15406 nm). The size of Pt nanoparticles was calculated according to the Scherrer equation, in which the most intense reflection at 2θ=36.6o was used. Temperature-programmed desorption of oxygen (O2-TPD) was measured on an Automated Chemisorption Analyser (chemBET pulsar TPR/TPD, Quantachrome). In a typical measurement, the catalysts were pre-treated under purified air at 150 oC for 0.5 h in order to remove the adsorbed impurities. And then the oxygen was introduced to the surfaces of the catalysts for 30 min before O2-TPD measurement. Finally, samples were heat-treated to 800 oC with a heating rate of 10 °C/min under helium flow (100



mL/min), and the product was detected by TCD detector. For CO-TPD, the temperature of systems was ramped from room temperature to 800 oC with a heating rate of 10 oC/min under the flow of 10% CO/He with a flow rate of 50 ml/min. The X-ray photoelectron spectroscopy (XPS) test was operated under an Al Kα radiation (1486.6 eV), and the X-ray source carried out at 10 mA and 15 kV, on an Axis Ultra DLD. The working pressure was no more than 2×10−8 Torr. The XPS spectra were obtained at 0.1 eV step size. The binding energies data were previously treated, using C1s (284.6 eV) as a typical standard binding energies value.

2.3. Catalytic Tests. The catalytic oxidation performance evaluation of CO, HCHO and C2H4 was carried out in a continuous-flow fixed bed quartz reactor at room temperature with a length of 18 cm and an inner diameter of 0.9 cm. In a typical catalytic performance test, the sample of 200 mg was put in the middle of the reactor and sandwiched by quartz wool. For the test of CO and C2H4, the feeding gas was standard one with a precise concentration of 100 ppm, balance gas is purified air (21% O2/79%N2), and the flow rate was 50 ml/min. The concentrations of outlet CO and C2H4 were collected and analysed by a Shimazu gas chromatograph equipped with a methane convertor and flame ionization detector (FID) detector. The final conversion was obtained according to initial concentration and the outlet concentration as follows: 𝛸(%) = (

𝑐in −𝑐out 𝑐in

) × 100 (1)

X in the equation represents the conversion of CO and C2H4, cin is the initial CO (or C2H4) concentration before reaction, and cout means the CO (or C2H4) concentration in the after fix bed. For the test of HCHO oxidation, the initial concentration of HCHO was detected by UV-Vis spectroscopy, and the concentration of converted CO2 was measured by a gas chromatography equipped with a methane convertor and a FID detector. In this process, HCHO is turned into CO2 by catalyst, and then CO2 is converted into CH4 through methane convertor, which is finally detected by FID detector. For this test, since no other compounds containing carbon element could be detected except CO2 in the outlet stream, the concentration of CO2 could be regarded as the concentration of reacted HCHO. The conversion of HCHO could be measured as follows: HCHO conversion (%) =

[CO2 ]out vol.% [HCHO]invol.%

× 100 (2)

where, [CO2]out represents the CO2 concentration after reaction (vol.%), and [HCHO]in


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represents the initial HCHO concentration in the feeding stream (vol.%). Catalytic stability of Pt-GA was carried out at 20 oC, and other conditions were consistent with those of catalytic ability test mentioned above. .

3. RESULTS and DISCUSSIONS 3.1. Characterization of Pt-GA. The fabrication of the flexible Pt-promoted graphene aerogel monolith is illustrated in Figure 1. EG plays a role of both the solvent and reducing agent because of its high boiling point and high viscosity. It could be proved that EG could promotes the reduction of graphene oxide (GO) and Pt ions and then with the help of metal ion, facilitates the formation of 3D network by accelerating the self-assemble process. Moreover, the oxygen-containing functional groups of graphene oxide could be beneficial to the effective connection between graphene and nanoparticles, leading to the uniform distribution of Pt nanoparticles. During the polyol process, graphene oxide was highly dispersed into EG under ultrasonic treatment. Then a homogeneous suspension of GO with a concentration of 2 mg/mL could be obtained, which could is chemically stable in next few months. Then H2PtCl6 solution was added to the GO dispersion to form a stable suspension. Subsequently, the suspension was under the solvothermal treatment in which graphene oxide sheets were reduced and self-assembled by the interaction of the functional groups on graphene sheets to form a 3D graphene network with finely dispersed Pt nanoparticles. Finally, 3D Pt-promoted graphene aerogel monolith was obtained after replacing the solvent with de-ion water and freeze-drying. Thermo-gravimetric analysis (TGA) result is shown in Figure 2, which reveals the content of Pt in the synthesised graphene aerogel monolith is 1.1 %, being consistent with the designed value. In EG solvent, the 3D graphene aerogel structure is difficult to be formed without the participation of Pt species, indicating that Pt species play a significant role in the construction of 3D graphene sheets network. According to this result, Pt species are supposed to have the ability to improve the interconnection between graphene sheets which finally assemble into a network. A series of Pt-promoted graphene aerogel monoliths could be synthesized by adjusting Pt content from 1% to 5%, with no obvious differences being observed from macroscopic and microscopic morphologies (Figure S1, Figure S2 and Table S1). This indicates that the effect of Pt nanoparticles in the formation of network is so efficient that even a small amount of Pt nanoparticles is enough. Apparently, samples with higher content of Pt may show better catalytic activities, however those with lower Pt content cost less and are favourable in practical applications. Herein, we chose the graphene



aerogel monolith containing 1.1% Pt as the target sample (Pt-GA) to investigate its structure, morphology as well as catalytic oxidation performances.

Figure 1. (a) Preparation illustration of Pt-GA; (b) Optical photographs of Pt-GA. The obtained Pt-GA gives a low density of 20 mg/cm3 and a weight of 100 mg with a compress modulus of 0.6 MPa. As shown in Figure 1b, Pt-GA could support an iron disc of 400 g, and immediately return to the initial shape after the iron disc was removed. The synthesised Pt-GA exhibits some outstanding mechanical properties, including low density, high strength and excellent flexibility. Compared to the traditional Pt/C catalysts with irregular shapes, the Pt-promoted graphene aerogel monolith exhibits a unique flexible structure, which would be beneficial to its potential applications as a versatile heterogeneous catalyst.

Figure 2 Thermo-gravimetric analysis result of Pt-GA.


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Figure 3. SEM images (a), TEM image (b) and HRTEM image (c) of Pt-GA.

The SEM and TEM images were conducted to obtain a direct observation of the surface structure, morphology and the distribution of supported Pt particles. Figure 3a shows an interconnected, honeycomb-like three-dimensional porous architecture with interconnected framework of graphene sheets in Pt-GA, which provides adequate transport pathways for both reactant gases and products, and may be responsible for the good flexibility. No diffraction of crystal particles is observed in the SEM image, which indicates the high dispersion of Pt nanoparticles on the support. Besides, the black points on TEM image in Figure 3b responding to the Pt particles are decorated on the graphene sheets in high dispersion. Figure 3c shows the Pt nanoparticles with an average particle size about 5 nm. This highly dispersed in-plane coating structure could improve the Pt particles’ specific surfaces area and accessibility of the reactant molecules, which both promote the catalytic performance of the catalysts. Figure 4 shows the N2 adsorption-desorption isotherms and the corresponding DFT pore size distributions of Pt-GA, and the detailed porosity parameters are summarized in Table 1. Pt-GA shows a hysteresis loop and a typical IV adsorption isotherm in which capillary condensation could be found in a wide pressure range about 0.4-1.0, indicating the present of mesopore structure in this material 30. The specific surface areas (SBET) and total pore volumes (Vtotal) are 230.5 m2/g and 0.33 cm3/g, respectively. Remarkably, Pt-GA provides abundant mesopores with the pore diameter centered at 3.38 nm, while the common commercial sample Pt-C exhibits a wide pore size distribution from 1.8 nm to 10 nm 31-33. Although the existence of micropores could bring more surface area and enhance the adsorption of gases, facilitating the catalytic reaction, it also hinders the molecular internal diffusion of reactant and product gases. For the Pt-GA catalyst, the moderate content of mesopores distributed between 3 to 5 nm could



effectively decrease the internal diffusion resistance of reactant and product gases. Moreover, it could provide more easy accessible active sites for reactant gases, resulting in an accelerated heterogeneous reaction on Pt nanoparticle surfaces.

Figure 4. (a) Nitrogen adsorption-desorption isotherms and (b) pore size distribution of PtGA. Table 1. Pore structural parameters of Pt-GA Sample Pt-GA a

b

SBETa

Vtb

Dpc

(m2/g)

(cm3/g)

(nm)

230.5

0.33

3.38 c

BET specific surface area; total pore volume (P/P0 = 0.985); average pore diameter by DFT.

XRD patterns of GA and Pt-GA are displayed in Figure 5. The relatively intensive peaks at 2θ of 24o could be found in both patterns, indicating that the graphene oxide sheets are efficiently reduced34. Some weak and broad diffraction peaks located at 39.7o, 46.2o and 67.4o could be detected in the XRD patterns of Pt-GA, responding to the (111), (200), and (220) planes of pure metallic Pt (JCPDS card No. 65-2868)35, suggesting the existence of metallic Pt species in Pt-GA. However, no clearly sharp diffraction peaks of Pt species could be observed in Pt-GA, indicating that these Pt nanoparticles on GA are highly dispersed on the graphene


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sheets with a rather small size. The average particle size of Pt is about 4.2 nm, calculated according to the Scherrer equation, which is in consistent with the result of TEM observation in Figure 3c. These nano-sized Pt particles provide active sites for catalytic oxidation, and are beneficial for the catalytic performance of CO, HCHO and C2H4 removal.

Figure 5. XRD patterns of GA and Pt-GA.

Figure 6. Pt 4f7/2 and Pt 4f5/2 curves of Pt-GA.

XPS analysis measurements were performed to investigate the chemical value of Pt phases of Pt-GA sample, and the results are provided in Figure 6. XPS spectra of the Pt 4f are consisted of Pt 4f7/2 (71.4 eV) and Pt 4f5/2 (74.7 eV), which could be fitted with an energy separation of 3.3 eV with a theoretical ratio of 4:3, which belong to Pt (0). No peaks around 72.4 eV and 75.7 eV, which is related to the existence of Pt (Ⅱ) oxidation states, could be found in the XPS spectra of Pt-GA36. These results indicate that Pt species on the graphene aerogel monolith surface are mainly Pt metal, which fit the XRD results. The nanosized metallic Pt (0) species



provide the catalytic active sites for the oxidation of CO, HCHO and C2H4, which is responsible for the high catalytic performance of Pt-GA. For the traditional Pt-promoted catalysts, an additional pre-treatment for the reduction of Pt ions before catalytic test is necessary, including calcination37 or NaBH4 38 treatment. It is generally believed that these processes could also lead to the aggregation of nanoparticles on the catalyst surface because of the high temperature and the reforming of Pt crystals, which may decrease the performance in catalytic oxidation. However, in our work, the Pt species in Pt-GA are reduced by the reducing effect of ethylene glycol during the reduction of graphene sheets. Thus highly dispersed nanoparticles of Pt(0) could be obtained. This process is crucial to obtain the highly active Pt catalyst for the oxidation of CO, HCHO and C2H4.

Figure 7. O2-TPD profiles of Pt-GA and Pt-C.

The O2-TPD experiments were employed to investigate the surface oxygen adsorption behaviour of the catalysts and the results are shown in Figure 7. The adsorbed oxygen is generally changed in the following sequence: O2(ad)→O2-(ad) →O-(ad)→O2-(lattice). The physically adsorbed oxygen could be easily adsorbed onto and desorbed from the catalysts under 150 oC, displaying no peaks in the O2-TPD patterns. For the lattice O2- species, the binding energy is so strong that desorption is very difficult until the temperature over 700 oC. Therefore, the broad O2 desorption peak between 200 oC and 550 oC is ascribed to O2-(ad) and O-(ad) species, which plays an essential role for catalytic oxidation of CO, HCHO and C2H439.40. By further investigation of the O2-TPD profiles, it could be clearly observed that Pt-GA possesses a larger peak area than Pt-C, and the peak of Pt-GA shifts to higher temperature position as well. These results demonstrate that the synthesized Pt-GA catalyst could significantly promotes the O2 adsorption during the reaction, indicating a better performance


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for catalytic oxidation reaction.

Figure 8. CO-TPD profiles of Pt-GA and Pt-C.

During the catalytic reaction, the adsorption and desorption behavior of CO, HCHO and C2H4 molecules on the catalyst surfaces is also a key factor. In order to further investigate the adsorption and desorption behavior of reactant molecules on the catalyst surface, CO-TPD test was carried out. A mixed gas consisting of 5% CO and 95% He was used to reveal the activation ability of oxidation on catalyst surfaces. The result of CO-TPD is shown in Figure 8, and it is quite similar with the result in the previous O2-TPD result. A relative larger desorption peak of Pt-GA could be observed, indicating a larger number of active sites on Pt-GA. The Pt nanoparticles on graphene surface could provide abundant active sites which could not only activate the surface oxygen, but also improve the activation of the target gas molecules which leads to a high catalytic activity for CO, HCHO and C2H4.

3.2. Catalytic test The catalytic oxidation conversion profiles for CO, HCHO and C2H4 over Pt-GA and Pt-C catalysts are shown in Figure 9. The synthesized Pt-GA shows a high catalytic activity for CO, HCHO and C2H4, with a complete conversion at room temperature. In contrast, the commercial Pt-C catalyst could only achieve complete conversion of CO, HCHO and C2H4 at the temperature of 60 oC, 70 oC and 80 oC, respectively. It should be noted that the content of Pt in Pt-C is 5%, which is much more than that of Pt-GA. The unique 3D structure of graphene sheets and highly dispersed Pt nanoparticles of Pt-GA should be responsible for the supreme catalytic activity.



Figure 9. Conversion profiles for (a) CO, (b) HCHO and (c) C2H4 oxidation over Pt-GA and Pt-C.

Carbon-based catalysts are usually confronted with a main problem of oxidative combustion during operated at high temperature, which limits their applications. All the tests of Pt-GA could be carried out at a temperature that much lower than that of Pt-C, indicating that Pt-GA has a much safer operation temperature. Besides, an additional catalytic stability test for CO,


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HCHO and C2H4 was carried out to determine the catalytic ability of Pt-GA in practical applications.

Figure 10. Catalytic stabilities of Pt-GA for CO, HCHO and C2H4 oxidation.

The catalytic stabilities of GA-Pt for CO, HCHO and C2H4 oxidation are shown in Figure 10. Such result shows the time when catalytic activity of Pt-GA catalyst for CO, HCHO and C2H4 oxidation begins to decrease is 200 h, 140 h and 120 h, respectively. This result demonstrates that the Pt-GA catalyst is very stable in the oxidation process of CO, HCHO and C 2H4 with a concentration of 100 ppm for a long period of 100 h.

4. CONCLUSIONS In summary, 3D flexible Pt-promoted graphene aerogel monolith was prepared by a one-step solvothermal method and applied as a versatile catalyst for room-temperature removal of CO, HCHO and C2H4. With the introducing of Pt ions and ethylene glycol, the graphene sheets could be cross-linked into a 3D network which could offer short diffusion path of molecules and easier accessible active sites for catalytic oxidation. During the solvothermal process, Pt ions together with the graphene oxide sheets are efficiently reduced by ethylene glycol. Moreover, the agglomeration of Pt nanoparticles could be significantly inhibited by the graphene sheets, which greatly decreases the size of Pt nanoparticles. The Pt-promoted graphene aerogel monolith exhibits an excellent flexible and mechanical property with a low density of 20 mg/cm3 and a compress modulus of 0.6 MPa. For the catalytic reaction of CO, HCHO and C2H4, such monolith shows a high activity and all the target gas molecules could be completely oxidized at room temperature, which is superior to the commercial Pt-C catalyst. In addition, the monolith provides an excellent stability with a 100% conversion for longer than 72 h. Based on the unique structures, the flexible Pt-promoted graphene aerogel monolith displays the excellent catalytic performances for CO, HCHO and C2H4 oxidation at ambient temperature.



ASSOCIATED CONTENT Supporting Information SEM images of GA-Pt-1%, GA-Pt-5%, nitrogen adsorption-desorption isotherms and pore structural parameters of Pt-GA-1%, Pt-GA-5% and Pt-C.

ACKNOWLEDGMENTS This work is partly supported by the National Natural Science Foundation of China (No. U1710252 and No. 21506061), the Young Elite Scientists Sponsorship Program by CAST (2017QNRC001), the Fundamental Research Funds for the Central Universities (222201817001) and the Shanghai Rising Star Program (17QB1401700). REFERENCENS (1) Njagi, E. C.; Chen, C. H.; Genuino, H.; Galindo, H.; Huang, H.; Suib, S. L. Total Oxidation of CO at Ambient Temperature Using Copper Manganese Oxide Catalysts Prepared by A Redox Method. Appl. Catal., B 2010, 99, 103-110. (2) Yu, C.; Crump, D. A Review of the Emission of VOCs from Polymeric Materials Used in Buildings. Build. Environ. 1998, 33, 357-374. (3) Collins, J. J.; Ness, R.; Tyl, R. W.; Krivanek, N.; Esmena, N. A.; Hall, T. A. A Review of Adverse Pregnancy Outcomes and Formaldehyde Exposure in Human and Animal Studies. Regul. Toxicol. Pharm. 2001, 34, 17-34. (4) Martinez-Romero, D.; Bailen, G.; Serrano, M.; Guillen, F.; Valverde, J.M.; Zapata, P.; Castillo, S.; Valero, D. Tools to Maintain Postharvest Fruit and Vegetable Quality Through the Inhibition of Ethylene Action: A Review Crit. Rev. Food Sci. Nutr. 2007, 47, 543-560. (5) Zhang, J. H.; Cheng, D.; Wang, B. B.; Khan, I.; Ni, Y. B. Ethylene Control Technologies in Extending Postharvest Shelf Life of Climacteric Fruit. J. Agr. Food Chem. 2017, 65, 73087319. (6) Moghadam, H. Z.; Kheirkhah, B.; Kariminik, A. Ethylene Removal by Bio-Filters in Order to Increase Storage Life of Bananas. Int. J. Life Sci. 2015, 9, 62-65. (7) Baur, G. B.; Beswick, O.; Spring, J.; Yuranov, I.; Kiwi-Minsker, L. Activated Carbon Fibers for Efficient VOC Removal from Diluted Streams: The Role of Surface Functionalities. Adsorption 2015, 21, 255-264. (8) Zhou, Y.; Zhou, L.; Zhang, X. H.; Chen, Y. L. Preparation of Zeolitic Imidazolate Framework-8/Graphene Oxide Composites with Enhanced VOCs Adsorption Capacity.


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