Atomistic Site Control of Pd in Crystalline MnO₂ Nanofiber for Enhanced Electrocatalysis

Oxides supported precious metals have wide applications in (electro-)catalysis. Although single atom dispersion is known as the most efficient metal utilization strategy, the dependence of the catalytic activity on different sites consisted of various anchoring sites for single atoms is largely unknown. Here, the electrocatalytic activities of crystalline α-MnO₂ with atomistic Pd locating at different sites including substitutional, tunnel, and surface-bound sites are first predicted, and then experimentally validated by applying different synthetic methods including hydrothermal reaction and impregnation-calcination. The quantum chemistry calculations together with experimental characterization suggest that substitutional Pd/MnO₂ possesses higher activity than the other samples due to the favorable geometric and electronic structures. Substitutional Pd can work synergistically with vicinal Mn sites toward cleavage of O-O bonds. This work provides a comprehensive understanding on the impact of atomistic anchoring site and advances the reliable control over the electrocatalytic performance of oxide-supported single atoms.