Self-adjusting Cr−N4 sites with peripheral engineering: diversifying catalyst library for selective O2 reduction to H2O2 in acidic media

Electrochemical two-electron oxygen reduction reaction (2e − ORR) serves as an appealing approach for green hydrogen peroxide (H 2 O 2 ) production. However, the corresponding progress in efficient non-precious metal catalysts for acidic 2e − ORR has not kept pace, with the research model being almost confined to Co-based system. Here, guided by molecular dynamics simulations, the active nature and origin of pyrolyzed Cr−N 4 catalysts for ORR are unveiled, wherein the over-strong oxygen affinity of the Cr center is counterbalanced by a spontaneous axial O-coordination. By creating an oxidation-induced electron-deficient environment, the Cr−N 4 can be flexibly tailored for selective H 2 O 2 formation. A single-atom Cr−N 4 /C(O) catalyst is developed experimentally, which rivals and even slightly outperforms its Co-based counterpart in terms of selectivity (92% versus 71%) and productivity (202 versus 145 mmol g cat −1  h −1 ) for H 2 O 2 . More encouragingly, the Cr-based catalysts exhibit minimal reactivity towards H 2 O 2 -related side reactions, with the metal component being robust against leaching. This research marks the first identification of pyrolyzed Cr−N 4 catalysts as competent for acidic two-electron O 2 reduction to H 2 O 2 . The innovative models and insights offer profound guidance for the design of future-generation catalysts for electrochemical H 2 O 2 synthesis.