Highly Selective Oxygen Reduction to Hydrogen Peroxide on aCarbon-Supported Single-Atom Pd Electrocatalyst br

Selective electrochemical two-electron oxygen reduction is a promisingroute for renewable and on-site H2O2generation as an alternative to theanthraquinone process. Herein, we report a high-performance nitrogen-coordinatedsingle-atom Pd electrocatalyst, which is derived from Pd-doped zeolitic imidazolateframeworks (ZIFs) through one-step thermolysis. High-angle annular dark-fieldscanning transmission electron microscopy (HAADF-STEM) combined with X-rayabsorption spectroscopy verifies atomically dispersed Pd atoms on nitrogen-dopedcarbon (Pd-NC). The single-atom Pd-NC catalyst exhibits excellent electrocatalyticperformance for two-electron oxygen reduction to H2O2, which shows similar to 95%selectivity toward H2O2and an unprecedented onset potential of similar to 0.8 V versusrevisable hydrogen electrode (RHE) in 0.1 M KOH. Density functional theory (DFT)calculations demonstrate that the Pd-N4catalytic sites thermodynamically prefer*-Obond breaking to O-O bond breaking, corresponding to a high selectivity for H2O2production. This work provides a deep insight into the understanding of the catalytic process and design of high-performance 2e-ORR catalyst