Article Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Innovative Dual-Compartment Flow Reactor Coupled with a Gas Diffusion Electrode for in Situ Generation of H2O2 Peipei Ding,† Lele Cui,† Dan Li,‡ and Wenheng Jing*,† †
State Key Laboratory of Materials-Oriented Chemical Engineering, National Engineering Research Center for Special Separation Membrane, College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, P.R. China ‡ Jiangsu Jiayi Thermal Power Co., Ltd, Changzhou 213200, P.R. China
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S Supporting Information *
ABSTRACT: A novel electrochemical membrane reactor integrated with a gas diffusion cathode (GDE) is proposed to improve oxygen utilization and energy efficiency for hydrogen peroxide (H2O2) electrogeneration. The limit of the oxygen reduction reaction was broken in the presence of the gas diffusion layer via the beneficial use of the GDE. The pore structure and surface property of the GDE were carefully adjusted to obtain low-resistance gas transport channels. The effects of oxygen flow rate on electrogeneration of H2O2 were assessed, and the role of GDE in the improved system was elucidated in comparison to the traditional system. At a polytetrafluoroethylene content of 25% for the catalytic layer of the GDE, the maximum oxygen utilization efficiency was enhanced to 7.4% and the accumulated concentration of H2O2 reached 1230.0 mg/L, with a current efficiency up to 88.1%; energy consumption was reduced to 11.6 kWh/kg.
1. INTRODUCTION Electro-Fenton (EF) is an advanced oxidation process and is considered a promising and highly efficient technology to degrade refractory pollutants such as phenols, pesticides, dyes, landfill waste, and pharmaceuticals.1−3 In the EF process, H2O2 is continuously produced at the cathode through an oxygen reduction reaction (ORR) which can provide the hydroxyl radical (·OH) to nonselectively oxidize most organic compounds to CO2, water, and inorganic ions.4,5 For an efficient EF process, it is therefore of critical importance to continuously and effectively generate H2O2. It is well-established that the generation of H2O2 is highly dependent on the property of the cathode,6 which provides the transport pathway of oxygen and reaction chamber. Traditional immersion electrodes such as graphite,7,8 graphite felt,9,10 carbon sponge,11 activated carbon fiber,12,13 and carbon nanotubes14,15 can improve the utilization efficiency of oxygen by sparging pure oxygen or air into the solution. However, the efficiency of H2O2 production is still limited by the solubilization and the diffusion of oxygen.16−18 Use of a gas diffusion electrode (GDE) is an excellent way to enhance the utilization efficiency of oxygen, wherein oxygen or air is pumped in the pore structure of the GDE instead of dissolving into the solution. Generally, a GDE consists mainly of a gas diffusion layer for accessible oxygen transport and a catalytic layer for providing the active sites to carry out the ORR.19 Thus, the pore structure and surface properties of the GDE directly influence the ORR efficiency, and many successful © XXXX American Chemical Society
modifications of structural properties of the GDE have been made to enhance the ORR activity.20,21 Among these, the modification of GDE with polytetrafluoroethylene (PTFE) has attracted great attention because of its improved porosity and surface hydrophobicity and the resulting decrease in the oxygen transport resistance. However, the origin of the beneficial effect of the influence of PTFE on the microstructure of GDE and the electrode activity are still unclear. In this context it is necessary to explore further the synergistic effects between the PTFE and GDE supports. In addition to the cathode, the structure of the reactor also affects the storage and transport of H2O2. In the traditional single-chamber EF reactor,22−24 the generation of H2O2 can be diminished when it transports to the anode, leading to a decrease of oxygen utilization efficiency. To avoid this phenomenon, a double-chamber reactor with a separator was developed to prevent the penetration of H2O2.25 To date, various types of membranes have been employed in the EF reactor, such as glass frits, diaphragms, and cationic membranes.19,26 However, in the presence of a separator, the total energy consumption in the EF reactor improved greatly. In our recent work, we successfully demonstrated the use of a double-compartment flow reactor with a ceramic membrane as Received: Revised: Accepted: Published: A
January 20, 2019 March 30, 2019 April 3, 2019 April 3, 2019 DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research
Figure 1. Schematic diagram of the double-compartment reactor.
added dropwise to the carbon black solution. Subsequently, the prepared mixture was deposited uniformly on the plate of nickel foam as the catalytic layer. Similarly, the gas diffusion layer was fabricated on the other side of the nickel foam plate. Lastly, the obtained GDE was pressed into a mold at a pressure of 18 MPa and calcined for 1 h at 350 °C. 2.3. Electrolytic Cell. The H2O2 electrogeneration experiment was performed in a homemade double-compartment flow reactor, and the schematic diagram of the reactor is shown in Figure 1. In the double-compartment reactor the anolyte and catholyte were in separated electrolytic tanks and flowed with independent peristaltic pumps. Plexiglas sheets were used for fixing the electrode and the membrane, and copper plates placed between the plexiglass were current collectors. The GDE worked as the cathode, and the graphite felt worked as anode. A gas chamber was added on the outside of cathode with a volume of 2.28 cm3; the catalytic layer was in direct contact with the electrolyte, while the reactant O2 gas was passed through the gas diffusion layer from the gas chamber into the catalytic layer. The oxygen reduction reaction occurred at the gas−solid−liquid three-phase interfaces in the catalytic layer.21,27,28 In addition, the α-Al2O3 ceramic membrane was employed to separate the anolyte and catholyte and the electrolyte was circulated with a peristaltic pump. The oxygen reduction reaction experiment was carried out in 0.05 M Na2SO4 electrolyte solution. During the reaction process, O2 (99.9%) was continuously flowed into the gas chamber from an oxygen cylinder, modulating the flow rate using a rotor flow-meter. The H2O2 concentration of the cathode tank was analyzed at 20 min intervals. 2.4. Analytic Methods. The porous structure of the gas diffusion layer with different contents of PTFE were characterized with a mercury porosimeter (Poremaster GT60, Quantachrome). The surface morphology of GDE was analyzed using scanning electron microscopy (SEM). Linear sweep voltammetry (LSV) curves were investigated to evaluate the ORR activity in a three-electrode cell, where the GDE was employed as working electrode, a platinum plate (1 cm × 1 cm × 0.1 cm) as counter electrode, and a silver/silver chloride (Ag/AgCl) as reference electrode, using an electrochemical workstation (Gamry Instruments Reference 3000, United
separator for the generation of H2O2 with low energy consumption. Building on these successful studies, we studied the design of a GDE with a double-compartment flow reactor containing a ceramic membrane to enhance H2O2 production. The pore structure and surface property of the GDE were adjusted by the use of PTFE, and the influence of loading PTFE in the gas diffusion layer and catalytic layer were investigated, respectively. Moreover, the relationship between the performance of the reactor and structural parameters such as the utilization efficiency of oxygen, current efficiency, ORR activity, and stability were carefully investigated. This improved EF reactor would be highly promising and important for applications in the treatment of environmental pollutants.
2. EXPERIMENTAL SECTION 2.1. Materials. The cathode was prepared using carbon black (Vulcan XC 72R) and PTFE (60%, Shanghai Aladdin Biological Technology Co., Ltd.), while foam nickel (Kunshan TengErHui Electronic Technology Co., Ltd.) was used as the GDE substrate. Graphite felt (Shanghai Hongjun Industry Co., Ltd.) was used as the anode. All chemicals used in this study were of analytical grade. Na2SO4 and potassium titanium(IV) oxalate (K2 TiO(C2O 4) 2 ) were purchased from Xilong Chemical Industry Incorporated Co., Ltd. and Shanghai Aladdin Biological Technology Co., Ltd., respectively. The αAl2O3 ceramic membrane with an average pore size of 100 nm was prepared in the laboratory. Deionized water was used for preparation of solutions, and all the experimental operations were conducted at room temperature. 2.2. Preparation of GDE. The as-fabricated GDE consisted of a conductive catalytic layer (CL), a layer of nickel foam as the current collector, and a gas diffusion layer (GDL). Among these, a hydrophobic carbon black layer with a PTFE modification was prepared as the GDL, which would present high oxygen diffusivity and hinder the transport of water. It is noteworthy that the CL was prepared by the same method. Different from the GDL, the CL provided the threephase reaction activated sites and the reaction channel. Carbon black (0.15 g) was dispersed in the ethanol solution by ultrasound, and 60 wt % of a PTFE suspension then was B
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research States) with a scan rate of 20 mV/s. Before testing, O2 was bubbled for 20 min to saturate the electrolyte solution, and the bubbling was continued throughout the experiment. The concentration of H2O2 during the electrogeneration process was monitored by an ultraviolet−visible (UV−vis) spectrophotometer (UV759, Shanghai Instrument Analysis Instrument Co., Ltd.) at λmax = 400 nm using the potassium titanium(IV) oxalate method.29,30 The current efficiency (%) of H2O2 electrogeneration is defined as follows:23,31 CE (%) =
nFC H2O2V It
× 100%
(1)
where CH2O2 is the concentration of H2O2 (mol/L), F the Faraday constant (F = 96486 C/mol), n the number of electrons transferred during the oxygen reduction process, V the catholyte volume (L), I the applied current (A), and t the electrolysis time (s). The oxygen utilization efficiency (OE) was introduced to describe the percentage of sparged oxygen used for H2O2 generation and calculated using the following formula:32,33 OE =
n H2O2RT PVA
× 100%
Figure 2. SEM images of the gas diffusion layer surface of the GDEs with (a) 50% PTFE, (b) 65% PTFE, (c) 75% PTFE, and (d) 80% PTFE.
with the PTFE modification, which was beneficial for oxygen transport. Figure 3 shows the pore structure of the samples with different PTFE contents. As shown in Figure 3, an intense peak
(2)
where nH2O2 is the molar amount of the generated H2O2 (M), R the universal gas constant (R = 8.314 J mol−1 K−1), T the gas temperature (K), P the oxygen partial pressure in the air feed stream (Pa), and VA the total aeration volume (m3). Energy consumption (EC; kWh/kg) of the electrogenerated H 2 O 2 can be calculated according to the following formula:25,34 EC (kWh/kg) =
1000UIt C H2O2V
(3)
where U is the average cell voltage (V). The Kozeny−Carman (K−C) equation was employed to calculate gas permeability in the gas diffusion layer, which is a semiempirical formula:35,36 K=
φn + 1 C = 180/λmean 2 C(1 − φ)n
Figure 3. Pore size distribution in the gas diffusion layer.
(4)
where ϕ is the porosity and λmean is the mean pore diameter; the value of the exponential n is 2, and constant C is the Kozeny−Carman constant.
of the pore volume distribution was observed at a pore size of ∼45 nm, which decreased with the increase of PTFE, especially at a PTFE content of 80%, where a secondary peak occurred at a pore size of ∼4 μm. This was mainly attributed to the aggregation of CB particles, which were bound together by the appeared PTFE as adhesive during the roll-pressing process, and the larger pore size formed owing to the assembling of the aggregating CB particles, making the average pore size enlarged with an increase of the PTFE content (Table 1). Moreover, in the presence of PTFE, the PTFE fibers could contract during the sintering process, forming a loose structure. Therefore, the
3. RESULTS AND DISCUSSION 3.1. Characterization of GDE. During the oxygen reduction process, the gas diffusion layer of the GDE mainly provided the transport pathway for the oxygen, which was highly dependent on the surface property and structure.20 Figure 2 shows the surface morphology of the GDE with various PTFE contents. It can be seen from the figure that the gas diffusion layer of the GDE presents a loose framework and the interconnected porous microstructure. The PTFE fiber occurs between the carbon black particles, and this phenomenon becomes more obvious with the increase in the PTFE content. It is noteworthy that the aggregation of PTFE fiber occurred when the PTFE content reached 80%. In addition, the surface hydrophobicity of the GDE was detected. As PTFE is a typical hydrophobic material, the contact angle of the diffusion layers increased with the PTFE content, indicating the diffusion layers became more hydrophobic
Table 1. Porous Structural Characteristics of Different PTFE Contents
average pore diameter (μM) porosity (%) K−C equation permeability (×10−3 D) C
50% PTFE
65% PTFE
75% PTFE
80% PTFE
0.044 44.53 1.501
0.071 71.05 1.626
0.079 79.53 1.887
0.074 74.33 1.422
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Industrial & Engineering Chemistry Research porosity of the diffusion layer was enhanced with the increase of PTFE content. However, when the PTFE content was 80%, the porosity decreased resulting from the aggregation of the fibers, which was consistent with the results of the SEM analysis. To further evaluate the gas permeability of the gas diffusion layer, the K−C equation was employed. As expected, the 75 wt % PTFE exhibited the highest gas permeability of 1.887 × 10−3 darcy (μm2) because of its high porosity, indicating that the accessibility and transport of oxygen may be enhanced. In view of this, 75 wt % PTFE was chosen as the optimal amount for gas diffusion layer preparation. 3.2. Comparison of the Two Types of Membrane Reactors. In the presence of the gas diffusion layer, oxygen can be directly transported to the solid−liquid interface and participates in the reaction, breaking the limit of the dissolved oxygen,19,21 whereby the oxygen utilization efficiency could be promoted and the generation rate of H2O2 could be accelerated. To verify this, the E-Fenton experiment was carried out using a traditional dual-compartment membrane reactor (MR) and a dual-compartment reactor integrating a GDE (GDE-MR), whose schematic diagrams are presented in Figure 4. In both reactors, an α-Al2O3 ceramic membrane with
Figure 5. Comparison of two reactors on the yield of H2O2 and the oxygen utilization efficiency (OE). Conditions: using CB/PTFE = 65% as catalytic layer, 75% PTFE as gas diffusion layer, CNa2SO4= 0.05 M, I = 110 mA, FO2= 20 mL/min, Fsolution= 1000 μL/min.
the traditional MR showed 220.3 mg/L and 0.7%, indicating that the GDE-MR with a modified gas diffusion layer enhanced the reaction process. In addition to the microstructure of the GDE, the oxygen flow rate also deeply influenced the reaction efficiency in the EF reaction process. Figure 6 shows the produced amount of H2O2 and the current efficiency of the reactor with different oxygen flow rate. It can be seen that no H2O2 was produced during the reaction process when nitrogen was introduced; therefore, the current efficiency was zero. However, the production rate of H2O2 can be greatly enhanced when there is ambient oxygen and/or extra oxygen adding in the gas chamber (Figure 6a). The results clearly show an increase in the rate of H2O2 generation with increased oxygen flow rate owing to enhanced oxygen mass transfer. However, the increase in the rate of H2O2 generation was not obvious when the oxygen flow rate was higher than 10 mL/min. A similar phenomenon was also observed in the current efficiency. Therefore, considering the economic benefits and the reaction efficiency, the optimized oxygen flow rate was fixed at 10 mL/min. 3.3. Electrocatalytic Activity of CL. The pore properties of the catalytic layer were also investigated, and the results are shown in Figure 7. The different catalytic layers (CB/PTFE = 50%, 65%, 75%, and 80%) were marked as 20% PTFE, 25% PTFE, 35% PTFE, and 50% PTFE, respectively. It can be seen from these that all the catalytic layers presented a clear hysteresis loop within the relative pressure range of ∼0.1−1, indicating a mesoporous structure.37 The corresponding pore size distribution curve (Figure 7b) showed that the catalytic layer presented an average pore size of ∼3.5 nm apart from the samples with 50% PTFE, which exhibited a broader pore size distribution between 4 and 7 nm. The specific surface area of the samples was 115.1, 113.8, 84.9, and 42.3 m2/g, respectively. The contracting of the PTFE is the likely reason for the enhancement of the porosity and surface area during the sintering process. The catalytic layer provided the catalytic activity site for the ORR. As the gas−liquid−solid three-phase reactivity takes place on the surface of the catalytic layer,27 its surface area and hydrophilicity are directly related to the ORR activity. To evaluate the ORR activity, the LSV with different PTFE content in the catalytic layer was investigated (Figure 8a). In this study, the catalytic layer with 25% PTFE presented a
Figure 4. Schematic diagrams of the double-compartment reactor: (a) oxygen is injected into the catholyte and (b) oxygen flows into the gas chamber.
a thickness of 1.8 mm was employed to avoid the decomposition of H2O2, whose conductivity of 5.593 × 10−3 S/cm is comparable to the 5.188 × 10−3 S/cm (Table S1) of the Nafion-117 membrane. However, different from the traditional MR, oxygen enters into the gas diffusion layer from the gas chamber and diffuses to the catalyst layer in the GDE-MR. Figure 5 shows the yields of H2O2 and oxygen utilization efficiency in the two reactors. As excepted, the GDE-MR exhibited a higher production of H2O2 of 1159.9 mg/L and higher oxygen utilization efficiency of 3.5%, while D
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Industrial & Engineering Chemistry Research
Figure 6. Effect of oxygen flow rate on (a) the yields of H2O2 and (b) current efficiency. Conditions: CNa2SO4 = 0.05 M, I = 110 mA, and Fsolution= 1000 μL/min.
Figure 7. N2 adsorption−desorption isotherm and pore size distributions of catalyst layers with different PTFE contents.
Figure 8. LSV curves of different PTFE contents in catalyst layer (conditions: scanning rate 20 mV/s, 0.05 M Na2SO4, oxygen saturation). Inset of panel b: the corresponding K−L plots at different potentials.
for the catalytic layer with 25% PTFE at the selected potential range, implying that the ORR process on the cathodes is dominated by a two-electron pathway, similar to the n obtained by the other three catalytic layers (Figure S1). This is mainly because the content of PTFE does not affect the reactivity of the catalytic layer but has a greater influence on the reaction site. This was consistent with the results of the Figure 8a. In the next series of experiments, the performance of the GDE-MR with different PTFE content was evaluated. As
higher response current compared with other catalytic layers, indicating it delivered the highest reaction activity of oxygen reduction as a result of its appropriate carbon black active site. Furthermore, LSV curves at different rotation rates were recorded. As shown in Figure 8b, the corresponding K−L plots for the GDE show good linearity with the slopes almost constant at the potential range of −0.5- −0.4 V (vs Ag/AgCl). The electron transfer number (n) per oxygen molecule in the ORR was calculated according to the K−L eqs (eqs 2 and 3 in the Supporting Information). The n is calculated to be 2.1−2.3 E
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Industrial & Engineering Chemistry Research
Figure 9. Effect of various PTFE contents in the CL: (a) the yields of H2O2 and (b) current efficiency. Conditions: CNa2SO4 = 0.05 M, I = 110 mA, FO2 = 10 mL/min. and Fsolution= 1000 μL/min.
excepted, the 25% PTFE presented the highest H2O2generating concentrations of 1230.0 mg/L and the highest current efficiency of 88.1% after 240 min (Figure 9). Although the catalytic layer with less PTFE content delivered a relatively higher surface area and more active sites, the catalytic layer with less PTFE exhibited more hydrophilicity and increased oxygen transport resistance in the hysteresis of the oxygen reduction reaction.38,39 To summarize, the catalytic layer with 25% PTFE delivered an excellent catalytic performance under the two effects. 3.4. Stability of the GDE Cathode System. For practical applications, the stability of the cathode is essential. In view of this, the continuous operation of the cathodes was investigated, and the results are displayed in Figure 10. After running 15
Figure 11. Contact angles between the electrolyte and the cathode on the surface of catalytic layer with different PTFE contents with and without a 110 mA applied current. Figure 10. Stability test of GDE in 15 continuous runs for H2O2 generation (conditions: CNa2SO4 = 0.05 M, I = 110 mA, FO2 = 10 mL/ min, and Fsolution = 1000 μL/min).
which can be explained by the electro-wetting theory.40 Especially, the wettability of catalytic layer with 20% PTFE changed from hydrophobic to hydrophilic under an external electric field, whose contact angle decreased to 75°. The electrolyte could permeate into the electrode and increase the transport resistance of the oxygen, resulting in inhibition of the oxygen reduction reaction. 3.5. Oxygen Utilization Efficiency and Energy Consumption. As the OE and EC were important indices for evaluation of the H2O2 production process, the OE and EC of the designed reactor were calculated and compared with the reported literature (Table 2). It can be seen that the immersed electrodes such as graphite or graphite felt mostly presented a relatively low accumulated concentration of H2O2 and oxygen
times, no significant reduction of H2O2 was observed when the content of PTFE was more than 25% in the catalytic layer. When the PTFE content was 20%, the yield of H2O2 dramatically decreased from 743.4 to 254.8 mg/L after 15 runs. To clarify this, the surface wettability of the catalytic layer was measured using the 0.05 M Na2SO4 solution, and the results are shown in Figure 11. As a result, the contact angle of the samples gradually decreased from 127° to 105° with the decrease of the PTFE contents. When an external current of 110 mA was applied, the contact angle remarkably decreased, F
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research Table 2. Comparison of the Performance Data with Literature Values cathode material graphite graphite felt graphite felt GDE GDE GDE GDE GDE
H2O2 generation (mg/L)
experimental conditions cathode area = 10.5 cm2, V = 500 mL, pH 3, 0.1 M Na2SO4, E = −0.65 V vs SCE, O2 flow rate = 0.33 L/min cathode area = 10 cm2, V = 130 mL, pH 6.4, 0.05 M Na2SO4, E = −0.65 V vs SCE, O2 flow rate = 0.4 L/min cathode area = 9.4 cm2, V = 200 mL, pH 2, 0.05 M Na2SO4, I = 50 mA, O2 flow rate = 0.20 L/min V = 100 mL, pH 3.0, I = 33 mA/cm2, 0.05 M Na2SO4, air flow rate = 200 mL/min cathode area = 4 cm2, V = 200 mL, pH 3, I = 20 mA/cm2, 0.05 M Na2SO4, air flow rate = 2 L/min cathode area = 14 cm2, V = 200 mL, pH 7, 0.05 M Na2SO4, I = 35.7 mA/cm2, air flow rate = 0.50 L/min cathode area = 16 cm2, V = 80 mL, pH 7, U = 6 V, 0.08 M Na2SO4, air flow rate = 100 mL/min (21% O2) cathode area = 3.8 cm2, V = 250 mL, pH 3, I = 110 mA, 0.05 M Na2SO4, air flow rate = 10 mL/min
■
utilization efficiency. In contrast, the EF reactor with a GDE exhibited a higher OE (0.13%−4.02%). In the present work, OE in H2O2 generation was even more enhanced to 7.4% (cathode area = 3.8 cm2, V = 200 mL, I = 110 mA, 0.05 M Na2SO4, Fsolution = 1000 μL/min, and FO2= 10 mL/min), and the energy consumption was 11.6 kWh/kg after 240 min. In conclusion, the improved double-compartment ceramic membrane flow reactor coupled with a GDE delivered a satisfactory performance for oxygen utilization efficiency as well as increased H2O2 production and reduced energy consumption.
CE (%)
0.04
63−73
0.01
87
260.7
0.20
75.7
595
0.9
47
589
0.13
93
566
1.93
51−88
420
1754.92
4.02
85.7
1230.0
7.4
88.1
EC (kWh/kg)
references 7 10
4.8
25
20.84
28 31
15.9
40 41
11.6
present work
AUTHOR INFORMATION
Corresponding Author
*Tel.: +86-25-83589136. Fax: +86-25-83172292. E-mail:
[email protected]. ORCID
Wenheng Jing: 0000-0002-1919-9932 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This research work was supported by the National Natural Science Foundation of China (21676139), the Higher Education Natural Science Foundation of Jiangsu Province (15KJA530001), the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), Research Fund of State Key Laboratory of Materials-Oriented Chemical Engineering (ZK201604), the Key Scientific Research and Development Projects of Jiangsu Province (BE201800901), and Natural Science Foundation of Jiangsu Province (BK20160297).
4. CONCLUSIONS In summary, a double-compartment ceramic membrane flow reactor with a GDE was developed for the EF reaction and delivered a superior performance. The H2O2 production, oxygen utilization efficiency, energy consumption, and current efficiency parameters were greatly improved using the system in comparison to reported literature. The pore structure and surface hydrophilia of the catalytic layer and gas diffusion layer with PTFE modification were systematically investigated. In the presence of the gas diffusion layer, the oxygen utilization efficiency was remarkably enhanced and reduced the energy consumption. In addition, the catalyst layer with 25% PTFE presented the highest H2O2 production and oxygen utilization efficiency, which were higher than reported results. The development of promising EF devices is anticipated by the use of this novel technology for various gas utilization efficiency applications.
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OE (%)
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REFERENCES
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.9b00358. Analytical methods, resistance and conductivity of different membranes (Table S1), LSV curves of different PTFE contents in catalyst layer (Figure S1), and performance comparison of three different cathodes (Figure S2) (PDF) G
DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
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DOI: 10.1021/acs.iecr.9b00358 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
