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《International Journal of Hydrogen Energy》2020,45(8):5430-5437
In this study, composite cation exchange membranes (CEM) were developed. With the experience from widely studied proton exchange membrane fuel cells (PEMFC), sulfonated polyether ether ketone (SPEEK) was prepared to be a more effective and cheaper ionomer alternative to the industry standard Nafion ®. SPEEK polymer membrane can reach sufficient ionic conductivities but have some mechanical and chemical stability problems (at a high degree of sulfonations (DS)). Therefore, in order to optimize the membrane, composite mixing with a well-known organic/inorganic clays called Cloisite® 15A, Cloisite ® 30B and MMT were used. Test cells for both single-cell and conductivity were designed and constructed. The ionic conductivity cell was different than the ones used in most studies, measuring conductivity in-plane with 4 probes using EIS. The membranes were characterized for their proton conductivity with electrochemical impedance spectroscopy (EIS), for DS with H NMR, water uptake, and fuel cell performance tests. First results showed that the acidic sulfonic groups of SPEEK interacted with organic/inorganic clays and as a result of partial barrier the ionic conductivity was decreased but power densities were increased. SPEEK-Cloisite® 30B composite membrane has given 40 mW/cm2 power density value which is higher than pure SPEEK membrane (35 mW/cm2). The proton conductivities of the final composite membranes were close to bare SPEEK membranes which are 0,065 and 0,075 S/cm for SPEEK-Cloisite ® 30B and pristine SPEEK, respectively. 相似文献
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《International Journal of Hydrogen Energy》2020,45(60):35006-35012
Fuel cells are promising alternative energy converters in terms of preventing pollution, efficiency, and noise. Direct borohydride fuel cells (DBFCs) which are defined as a sub-class of polymer electrolyte membrane fuel cells (PEMFCs) and direct liquid fuel cells (DLFC) have increased attention recently since they offer a solution for hydrogen storage problem. However, the commercialization of DBFC is hindered by the need of high platinum loadings. Therefore, reducing the platinum content is crucial to develop cost-effective DBFC without compromising performance. This research focuses on the effects of operational parameters on the DBFC performance with low level Pt/C catalyst loading (anode: 0.32 mg/cm2, cathode: 0.36 mg/cm2). The gas diffusion electrode was prepared by spray-coating technique. The peak power density of 19.95 mW/cm2 was obtained at 80 °C when 1 mL/min was used as a flow rate of fuel. 相似文献
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We studied the borohydride oxidation reaction (BOR) by voltammetry in 0.1 M NaOH/10−3 M BH4− on carbon-supported Pt, Ag and alloyed PtAg nanoparticles (here-after denoted as Pt/C, Ag/C and Pt–Ag/C). In order to compare the different electrocatalysts, we measured the BOR kinetic parameters and the number of electrons exchanged per BH4− anion (faradaic efficiency). The BOR kinetics is much faster for Pt/C than for Ag/C (iPt=0.15, iAg=3.1×10−4 A cm−2 at E=−0.65 V vs. NHE at 25 °C), but both materials present similar Tafel slope values. The n value involved in the BOR depends on the thickness of the active layer of electrocatalysts. For a “thick layer” (approximately 3 m), n is nearly 8 on Pt/C and 4 on Ag/C, whereas n decreases for thinner Pt/C active layers (n2 for thickness <1 m). These results are in favour of the sequential BH4− hydrolysis (yielding H2) followed by hydrogen oxidation reaction (HOR), or direct sequential BOR on Pt/C, whereas Ag/C promotes direct but incomplete BOR (Ag has no activity regarding hydrogen evolution reaction, HER). The n value close to 8 for the thick Pt/C layer displays the sufficient residence time of the molecules formed (H2 by heterogeneous hydrolysis or BOR intermediates) within the active layer, which favours the complete HOR and/or BOR. Two PtAg/C nanoparticles alloys have been tested (noted APVES-4C and APVES-E1). They show different behavior; the borohydride oxidation reaction kinetics is faster on APVES-E1 than on APVES-4C (b=0.15, and b=0.31 V dec−1, A cm−2, respectively, at 25 °C), but the n values are higher on APVES-4C than APVES-E1 (nearly 8 vs. 3, respectively, at 25 °C). These discrepancies probably originate from the heterogeneity of such bimetallic materials, as observed from physicochemical characterizations. 相似文献
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The carbon-supported Pt-modified Au nanoparticles were prepared by two different chemical reduction processes, the simultaneous chemical reduction of Pt and Au on carbon process (A-AuPt/C) and the successive reduction of Au then Pt (B-AuPt/C) on carbon process. These two catalysts were investigated as the anode catalysts for a direct borohydride fuel cell (DBFC) and Au nanoparticles on carbon (Au/C) were also prepared for comparison. The DBFC with B-AuPt/C as the anode catalyst shows the best anode and fuel cell performance. The maximum power density with the B-AuPt/C catalyst is 112 mW cm−2 at 40 °C, compared to 97 mW cm−2 for A-AuPt/C and 65 mW cm−2 for Au/C. In addition, the DBFC with the B-AuPt/C catalyst shows the best fuel utilization with a maximum apparent number of electrons (Napp) equal to 6.4 in 1 M NaBH4 and 7.2 in 0.5 M NaBH4 as compared to the value of Napp of 8 for complete utilization of borohydride. 相似文献
5.
Chun-Chen Yang Yingjeng James Li Shwu-Jer Chiu Kuo-Tong Lee Wen-Chen Chien Ching-An Huang 《Journal of power sources》2008
A new poly(vinyl alcohol)/hydroxyapatite (PVA/HAP) composite polymer membrane was synthesized using a solution casting method. Alkaline direct borohydride fuel cells (DBFCs), consisting of an air cathode based on MnO2/C inks on Ni-foam, anodes based on PtRu black and Au catalysts on Ni-foam, and the PVA/HAP composite polymer membrane, were assembled and investigated for the first time. It was demonstrated that the alkaline direct borohydride fuel cell comprised of this low-cost PVA/HAP composite polymer membrane showed good electrochemical performance. As a result, the maximum power density of the alkaline DBFC based on the PtRu anode (45 mW cm−2) proved higher than that of the DBFC based on the Au anode (33 mW cm−2) in a 4 M KOH + 1 M KBH4 solution at ambient conditions. This novel PVA/HAP composite polymer electrolyte membrane with high ionic conductivity at the order of 10−2 S cm−1 has great potential for alkaline DBFC applications. 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(1):452-463
Searching for non-precious metal anode catalysts with high catalytic activity and capable of inhibiting hydrolysis side reactions is very important for direct borohydride fuel cell (DBFC). In this work, the as-cast AB5 alloy powders are firstly mixed with CNTs in a ratio of 1:9. Then the mixture of AB5 alloy and CNTs is ball milled in different milling time. Finally, the CNTs/AB5 composite alloys are obtained. Not only the catalytic properties of the CNTs/AB5 composite alloys used as anode catalysts in DBFC, but also the electrochemical properties of the alloys have been investigated in detail. The research results indicate that, as the ball milling time is extended, the electrochemical properties and catalytic properties on ΒΗ4− of the CNTs/AB5 composite alloys become better first and then worsen. The CNTs/AB5 alloy milled 2 h exhibits the best electrochemical properties and catalytic properties. Furthermore, we predict that the electrochemical properties of the composite alloy are positively correlated with the catalytic properties as anode catalyst for DBFC. 相似文献
7.
Gholamreza RostamikiaAlfonso J. Mendoza Michael A. HicknerMichael J. Janik 《Journal of power sources》2011,196(22):9228-9237
Borohydride oxidation electrokinetics over the Au(1 1 1) surface are simulated using first-principles determined elementary rate constants and a microkinetic model. A method to approximate the potential dependent elementary step activation barriers based on density functional theory calculations is developed and applied to the minimum energy path for borohydride oxidation. Activation barriers of the equivalent non-electrochemical reactions are calculated and made potential dependent using the Butler-Volmer equation. The kinetic controlled region of the borohydride oxidation reaction linear sweep voltammogram over the Au(1 1 1) surface is simulated. The simulation results suggest that B-H bond containing species are stable surface intermediates at potentials where an oxidation current is observed. The predicted rate is most sensitive to the symmetry factor and the BH2OH dissociation barrier. Surface-enhanced Raman spectroscopy confirms the presence of BH3 as a stable intermediate. 相似文献
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Rare earth metal oxides(REMO) as cathode electrocatalysts in direct borohydride fuel cell(DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V. 相似文献