Balancing Activity and Selectivity in Two‐Electron Oxygen Reduction through First Coordination Shell Engineering in Cobalt Single Atom Catalysts
Kai Sun, Ruihu Lu, Yuge Liu, J. K. G. Webb, Muhammad Hanif, Yufei Zhao, Ziyun Wang, Geoffrey I. N. Waterhouse
Abstract
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.