Single atom catalysts for use in the selective production of hydrogen peroxide via two-electron oxygen reduction reaction: Mechanism, activity, and structure optimization

Electrochemically synthesizing H2O2 via two-electron oxygen reduction reaction (2e- ORR) is a promising alternative to substitute the energy-intensive anthraquinone process. In the past years, single-atom catalysts (SACs) have been proposed and widely studied as efficient candidates for catalyzing 2e- ORR, which greatly advances in the H2O2 production. Although SACs with different metal centers and coordination structures have been fabricated, the obscure catalytic mechanism impedes their structure design. This critical review summarized the recent progress on 2e- ORR catalyzed by SACs with noble metals, transition metals, and bimetallic as active sites and elaborates on the significance of the binding intensity of *OOH intermediate and active sites in determining the reaction pathway. Additionally, crucial factors including coordination environment, substrate type, and O2 adsorption configuration that affect SACs performance was discussed. Finally, the structure-performance relationship was unraveled via thoroughly analyzing theoretical justification and experimental findings and future perspectives were envisaged. [Display omitted] •Sophisticated theoretical approaches for evaluating two-electron ORR are presented.•SACs with bimetallic active sites and the geometric effects are summarized.•Reaction thermodynamic and crucial factors of two-electron ORR was discussed.•Future perspectives of SACs for use in two-electron ORR was envisaged.