CeO2 Modulates the Electronic States of a Palladium Onion-Like Carbon Interface into a Highly Active and Durable Electrocatalyst for Hydrogen Oxidation in Anion-Exchange-Membrane Fuel Cells

• Published in: ACS catalysis 2022-06, Vol.12 (12), p.7014-7029
• Main Authors: Ogada, Jimodo J., Ipadeola, Adewale K., Mwonga, Patrick V., Haruna, Aderemi B., Nichols, Forrest, Chen, Shaowei, Miller, Hamish A., Pagliaro, Maria V., Vizza, Francesco, Varcoe, John R., Meira, Debora Motta, Wamwangi, Daniel M., Ozoemena, Kenneth I.
• Format: Article
• Language: English
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.2c01863

This study reports the preparation, characterization, and electrocatalytic properties of palladium-based catalysts containing ceria (CeO2) on carbon black (CB) and onion-like carbon (OLC) supports. The electrocatalysts (Pd–CeO2/CB and Pd–CeO2/OLC) exhibit a large specific surface area, pore volume, and small particle size, as well as enhanced interfacial interaction and synergy among Pd, CeO2, and OLC in Pd–CeO2/OLC that are valuable for improved electrocatalysis. The presence of CeO2 in Pd–CeO2/OLC induces ca. 7% defects and modifies the electronic structure of the Pd/OLC interface, significantly improving the electrical conductivity due to enhanced charge redistribution, corroborated by density functional theory (DFT) calculations. Pd–CeO2/OLC displays the lowest adsorption energies (H*, OH*, and OOH*) among the series. For the hydrogen oxidation reaction (HOR), Pd–CeO2/OLC delivers significantly enhanced HOR (mass-specific) activities of 4.2 (8.1), 13.2 (29.6), and 15 (78.5) times more than Pd–CeO2/CB, Pd/OLC, and Pd/CB, respectively, with the best diffusion coefficient (D) and heterogeneous rate constant (k). Pd–CeO2/OLC also displays less degradation during accelerated durability testing. In an anion-exchange-membrane fuel cell (AEMFC) with H2 fuel, Pd–CeO2/OLC achieved the highest peak power density of 1.0 W cm–2 at 3.0 A cm–2 as compared to Pd–CeO2/CB (0.9 W cm–2 at 2.2 A cm–2), Pd/OLC (0.6 W cm–2 at 1.7 A cm–2), and Pd/CB (0.05 W cm–2 at 0.1 A cm–2). These results indicate that Pd–CeO2/OLC promises to serve as a high-performing and durable anode material for AEMFCs.