Cerium dioxide restricted the growth of palladium nanoclusters for constructing Pd-O-Ce bridge bonds: Efficient oxygen reduction and formic acid oxidation reactions.

In direct formic acid fuel cells, the formic acid oxidation reaction (FAOR) takes place at the anode, and the oxygen reduction reaction (ORR) occurs at the cathode. Whereas the cathode of zinc-air batteries (ZABs) also involves the ORR, these three electrochemical reactions collectively constitute the core processes of related energy devices. The study of the catalytic performance of palladium (Pd)-based catalysts has become a research focus. This study explores the utilization of rare earth metal-organic frameworks to enhance the interface interactions between Pd and CeO. These frameworks facilitate the modulation of the electronic state of Pd, ensure site stability, and promote the generation of additional oxygen vacancies through bridge bonding between Pd-O-Ce. The Pd-CeO/C(1:2) catalyst in 0.5 M HSO exhibited high initial potential (0.86 V vs. reversible hydrogen electrodes (RHE)), half-wave potential (0.76 V vs. RHE), excellent ORR stability, and exceptional performance in ZAB cathodes with a power density reaching 195.4 mW·cm. Furthermore, in FAOR (0.5 M HSO + 0.5 M HCOOH) applications, this catalyst displays significantly higher activity (991.4 mA·mg) and stability than commercial Pd/C and Pt/C catalysts while maintaining excellent selectivity for formic acid decomposition. Theoretical calculations further prove that the formation of the Pd-O-Ce bridge bond is conducive to FAOR's direct reaction pathway and avoids CO toxicity. The Pd-CeO/C(1:2) catalyst is utilized in positive and negative electrodes within self-assembled H-type electrolytic cells, achieving open-circuit voltages superior to those offered by commercial catalysts, thus confirming its practical applicability.