Balancing Activity and Selectivity in Two‐Electron Oxygen Reduction through First Coordination Shell Engineering in Cobalt Single Atom Catalysts

Abstract The electrochemical two‐electron oxygen reduction reaction (2e − ORR) offers a potentially cost‐effective and eco‐friendly route for the production of hydrogen peroxide (H 2 O 2 ). However, the competing 4e − ORR that converts oxygen to water limits the selectivity towards hydrogen peroxide. Accordingly, achieving highly selective H 2 O 2 production under low voltage conditions remains challenging. Herein, guided by first‐principles density functional theory (DFT) calculations, we show that modulation the first coordination sphere in Co single atom catalysts (Co−N−C catalysts with Co‐N x O 4‐x sites), specifically the replacement of Co−N bonds with Co−O bonds, can weaken the *OOH adsorption strength to boost the selectivity towards H 2 O 2 (albeit with a slight decrease in ORR activity). Further, by synthesizing a series of N‐doped carbon‐supported catalysts with Co‐N x O 4‐x active sites, we were able to validate the DFT findings and explore the trade‐off between catalytic activity and selectivity for 2e − ORR. A catalyst with trans ‐Co‐N 2 O 2 sites exhibited excellent catalytic activity and H 2 O 2 selectivity, affording a H 2 O 2 production rate of 12.86 and an half‐cell energy‐efficiency of 0.07 during a 100‐hours H 2 O 2 production test in a flow‐cell.