Trace Sulfur‐Incorporation of Palladium Nanosheets to Boost the Oxygen Reduction Reaction

With a S: Pd feeding ratio of 1: 100, Pd nanosheets (denoted as S 0.01 ‐Pd NSs) with wrinkled nanosheet morphology and polycrystalline structure that are almost indistinguishable with pristine Pd NSs are synthesized via a facile one‐pot solvothermal process. Notably, the trace amount of S‐incorporation (0.83 atom%) distinctively altered the surface electronic structure of the Pd NSs and boosted the performance of the S 0.01 ‐Pd NSs as oxygen reduction reaction (ORR) electrocatalyst. The S 0.01 ‐Pd NSs exhibited a half‐wave potential of 0.940 V, 12 mV more positive than that of the Pd NSs, and improved durability. Theoretical calculations with density functional theory indicated that the d ‐band center of the Pd(111) surface would shift increasingly negative with the amount of S incorporated. Furthermore, the adsorption, activation and hydrogenation of O 2 , would change drastically when the S‐incorporation increased from 3S to 4S on Pd(111) surface. The free energy changes in sequential ORR steps on the 3S‐Pd(111) surface are optimized, leading to a lower estimated overpotential compared to pristine Pd(111); while on 4S‐Pd(111) surface, ORR process is suppressed. Such a trend is consistent with the outstanding catalytical performance of the S 0.01 ‐Pd NSs, demonstrating that the trace‐amount incorporation is the optimized strategy for doping S in Pd‐based catalysts.