Suppression of Hydrogen Peroxide Formation on Pt Using WO3 as Anode Co-Catalysts

Polymer electrolyte fuel cells (PEFCs) are emerging as promising candidates for next-generation energy systems, particularly for hydrogen vehicles and clean energy applications, due to their advanced high-power density production and efficiency. However, the commercialization of PEFCs is hindered by issues related to fuel cell durability, primarily caused by the chemical degradation of proton exchange membranes (PEMs) due to reactive oxygen-related radical attacks, notably generated through the production of hydrogen peroxide (H 2 O 2 ). Anode catalysts, such as carbon-supported platinum nanoparticles (Pt/C), play a vital role in facilitating the hydrogen oxidation reaction (HOR), which is accompanied by the undesired formation of H 2 O 2 due to oxygen gas (O 2 ) crossover from the cathode. As for the Pt surface, the structure is sensitive to H 2 O 2 production. Hence, minimizing H 2 O 2 generation while maintaining HOR activity by developing anode catalysts is necessary to suppress degradation. Tungsten oxide (WO 3 ) has emerged as an interesting active material due to its stability in acidic solutions and its ability to increase the rate of hydrogen oxidation by facilitating hydrogen spill-over from the Pt surface to WO 3 to generate hydrogen tungsten bronze (H x WO 3 ). [1, 2] This process enhances the availability of hydrogen on the Pt surface by effectively transferring hydrogen atoms from Pt to WO 3 . With more active sites available on the Pt surface, there is a higher likelihood of hydrogen oxidation, reducing the formation of H 2 O 2 as an intermediate product. This study aims to develop an anode catalyst by incorporating WO 3 nanoparticles into the Pt/C to suppress H 2 O 2 production during HOR, particularly in the presence of oxygen. The rotating ring-disk electrode (RRDE) technique was utilized to evaluate catalyst performance and detect H 2 O 2 generation during HOR. HOR activity and H 2 O 2 production rate measurements were conducted in H 2 -sat. and H 2 /air-sat. 0.1 M HClO 4 electrolyte at different temperatures (25, 40, and 60 ℃). The electrochemical measurements demonstrated that both Pt/C and WO 3 -Pt/C catalysts exhibited enhanced H 2 O 2 formation rates with increasing temperature. This observation underscores the significance of temperature as a modulator of catalytic performance and suggests the existence of temperature-dependent kinetic mechanisms governing H 2 O 2 generation during HOR. Moreover, the comparative analysis between Pt/C and WO 3 -Pt/C catalysts reveals distinct temperature-dependent behaviors. While both catalysts exhibit temperature-enhanced H 2 O 2 formation, the WO 3 -Pt/C catalyst demonstrated significantly reduced H 2 O 2 production at 0 V vs reversible hydrogen electrode (RHE) approximately 40% at 60 ℃ as compared with Pt/C, and it exhibited high HOR mass activity and surface activity across a broad temperature range. This suppression is attributed to the synergistic effect between platinum and tungsten oxide species, which facilitates improved HOR kinetics and H 2 O 2 selectivity. This study was supported in part by funds for the “R&D of novel anode catalyst” project in the “Collaborative industry-academia-government R&D project for solving common challenges toward dramatically expanded use of fuel cells” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. The authors thank Prof. Hiroyuki Uchida (The University of Yamanashi) for his kind advice. References: [1] A.C.C. Tseung, K.Y. Chen, Catal. Today 38 , 1997, 439. [2] J. Shim, C.R. Lee, H.K. Lee, J.S. Lee, E.J. Cairns, J. Power Sources 102 , 2001, 172.