Electrocatalysts for PEM Fuel Cells

Ioroi, Tsutomu; Siroma, Zyun; Yamazaki, Shinichi; Yasuda, Kazuaki

doi:10.1002/aenm.201801284

Cited by 167 publications

(130 citation statements)

References 191 publications

(581 reference statements)

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“…The carbon supports also isolate Pt NPs to maintain high electrochemical surface area and provide certain hydrophobic properties to avoid flooding of the catalyst layer by liquid water produced. However, one of the major concerns in the performance degradation of fuel cells is related to the electrochemical corrosion of the carbon support materials . The thermodynamic potential of carbon oxidation to carbon dioxide is 0.207 V versus the reversible hydrogen electrode (RHE), and the potential of a PEMFC cathode is typically in the range of 0.6–1.2 V versus RHE.…”

Section: Introductionmentioning

confidence: 99%

“…To develop catalyst supports that are stable at high potentials, a myriad of noncarbonaceous catalyst supports, including metal oxides, perovskites, nitrides, carbides, and sulfides, have been explored and show superior corrosion resistance as catalyst supports . The main problems of oxide and other noncarbonaceous supports are the relatively low electronic conductivity and low specific surface areas for anchoring the PMG NPs …”

Section: Introductionmentioning

confidence: 99%

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Intrinsic Effect of Carbon Supports on the Activity and Stability of Precious Metal Based Catalysts for Electrocatalytic Alcohol Oxidation in Fuel Cells: A Review

Zhang

Xiang

et al. 2020

ChemSusChem

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Electrocatalyst supports, in particular carbonaceous materials, play critical roles in the electrocatalytic activity and stability of precious metal group (PMG)‐based catalysts such as Pt, Pd, and Au for the electrochemical alcohol oxidation reaction (AOR) of fuels such as methanol and ethanol in polymer electrolyte membrane fuel cells (PEMFCs). Carbonaceous supports such as high surface area carbon provide electronic contact throughout the catalyst layer, isolate PMG nanoparticles (NPs) to maintain high electrochemical surface area, and provide hydrophobic properties to avoid flooding of the catalyst layer by liquid water produced. Compared to high surface area carbon, PMG catalysts supported on 1D and 2D carbon materials such as graphene and carbon nanotubes show enhanced activity and durability due to the intrinsic effect of the underlying carbonaceous supports on the electronic states of PMG NPs. The modification of the electronic environment, in particular the d‐band centers of PMG NPs, weakens the adsorption of AOR intermediates, facilitates breaking of the C−C bonds, and thus enhances the electrocatalytic activity of PMG catalysts. The doping of heteroatoms further facilitates the electrocatalytic activity for the AOR through the structural, bifunctional, and electronic effects, in addition to the enhanced dispersion of PMG NPs in the carbon support. The prospects for the development of effective PMG‐based catalysts for high‐performance alcohol‐fuel‐based PEMFCs is discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intrinsic Effect of Carbon Supports on the Activity and Stability of Precious Metal Based Catalysts for Electrocatalytic Alcohol Oxidation in Fuel Cells: A Review

Zhang

Xiang

et al. 2020

ChemSusChem

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“…We used a PtRu catalyst in place of Pt catalysts, since the former has higher CO-tolerance than Pt alone. [1,2] The results are shown in Figure 4. When the CO gas is passed through 0.1 M H 2 SO 4 containing both Rh-TAA/KB and PtRu/C or Rh-TAA-adsorbed PtRu/C, H 2 was clearly generated.…”

mentioning

confidence: 96%

“…CO-tolerant anode catalysts are required to counteract the negative impact of CO on PEFCs. [1,2] CO electro-oxidation (Eq. (1)) can decrease the concentration of CO at the anode, and hence this reaction helps to improve COtolerant anode catalysts for PEFCs.…”

mentioning

confidence: 99%

“…However, on Pt electrodes, this reaction needs extremely high overpotentials [4] , which leads to loss of performance and efficiency of PEFCs. While alloying Pt with a second metal such as Ru or Sn decreases these overpotentials, [1,2,5] overpotentials remain high. High overpotentials could also be a significant problem for amperometric CO sensors in terms of interference.We focused on complex-based electrocatalysts to achieve CO oxidation at low overpotentials.…”

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confidence: 99%

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Electrochemical CO oxidation by a Rh tetraaza[14]annulene‐based catalyst

et al. 2020

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Electrochemical CO oxidation catalyzed by Rh complexes of tetraaza [14]annulene was examined. Rh complexes on carbon black exhibit much higher CO oxidation activity than Rh porphyrins or conventional Pt alloy catalysts. The onset potential for CO oxidation is lower than 0 V vs. a reversible hydrogen electrode. As a result, a combination of electrochemical CO oxidation by Rh tetraaza [14]annulene and proton reduction by Pt catalysts generates slight electricity. The combined overall reaction is a water-gas shift reaction (CO + H 2 O!CO 2 + H 2 ). The co-presence of Rh tetraaza [14]annulene catalyst and Pt catalyst promotes the water-gas shift reaction.For several decades, CO electro-oxidation (Eq. (1)) has attracted considerable interest from researchers engaged in both basic science and studies on various applications.This reaction has been applied to the development of polymer electrolyte fuel cells (PEFCs). In stationary PEFC systems, a reformate gas of hydrocarbon is used as a fuel, and hence CO is inevitably contained in the anode gas. CO severely poisons the surface of a Pt anode and significantly decreases the performance of PEFCs. CO-tolerant anode catalysts are required to counteract the negative impact of CO on PEFCs. [1,2] CO electro-oxidation (Eq. (1)) can decrease the concentration of CO at the anode, and hence this reaction helps to improve COtolerant anode catalysts for PEFCs. This reaction also plays an important role in the design of an amperometric CO sensor. [3] Noble metal electrodes, exemplified by a Pt electrode, catalyze electrochemical CO oxidation. However, on Pt electrodes, this reaction needs extremely high overpotentials [4] , which leads to loss of performance and efficiency of PEFCs. While alloying Pt with a second metal such as Ru or Sn decreases these overpotentials, [1,2,5] overpotentials remain high. High overpotentials could also be a significant problem for amperometric CO sensors in terms of interference.We focused on complex-based electrocatalysts to achieve CO oxidation at low overpotentials. Veen et al. found that a Rh porphyrin catalyzes the electro-oxidation of CO at low overpotentials. [6] We found that the catalytic activity of Rh porphyrin electrocatalysts significantly depends on the ligand structure. [7] The activity increased with the use of an appropriate ligand and substituents. [7a,b] We demonstrated that a PEFC that uses a Rh porphyrin catalyst as an anode delivers high power when neat CO is supplied as a fuel. [8] A mechanistic analysis demonstrated that CO is adsorbed on a Rh atom in Rh porphyrin. [9] Rh porphyrin can be adsorbed on the PtRu catalyst, and the composite material acts as a CO-tolerant anode catalyst. [10] However, even when a state-of-the-art Rh porphyrin catalyst is used, some overpotential is left. Improvement of the porphyrin ligand alone might not be enough to decrease the CO oxidation potential. We tried to change macrocycle ligands to develop a catalyst that can oxidize CO at low overpotentials. We paid special attention to a dibenzo...

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