Selective oxygen electroreduction to hydrogen peroxide in acidic media:The superiority of single-atom catalysts

Two-electron oxygen reduction reaction(2e-ORR)provides an environmentally friendly direction for the on-site production of hydrogen peroxide(H_(2)O_(2)).Central to this technology is the exploitation of efficient,economical,and safe 2e-ORR electrocatalysts.This overview starts with the fundamental chemistry of ORR to highlight the decisive role of adsorbing intermediates on the reaction pathway and activity,followed by a comprehensive survey of the tuning strategies to favor 2e-ORR on traditional precious metals.The latest achievements in designing efficient and selective precious-metal-based single-atom catalysts(SACs)and metal-nitrogen-carbon(M-Nx/C)catalysts,from the aspects of material synthesis,theoretical calculations,and mass transport promotion,are systematically summarized.Brief introductions on the evaluation metrics for 2e-ORR catalysts and the primary reactor designs for cathodic H_(2)O_(2)synthesis are also included.We conclude this review with an outlook on the challenges and direction of efforts to advance electrocatalytic 2e-ORR into realistic H_(2)O_(2)production.