Boosting O₂ Reduction and H₂O Dehydrogenation Kinetics: Surface <i>N</i>‐Hydroxymethylation of <i>g</i>‐C₃N₄ Photocatalysts for the Efficient Production of H₂O₂

Abstract

Abstract g ‐C 3 N 4 photocatalysis is a safe and green approach for H 2 O 2 production, but the activity of pristine g ‐C 3 N 4 photocatalysts is unsatisfactory. At present, most of the modifications on g ‐C 3 N 4 photocatalysts for H 2 O 2 production have focused on thermodynamic processes, few have considered the kinetic aspects. Herein, the surface N ‐hydroxymethylation of g ‐C 3 N 4 photocatalysts for the efficient kinetic production of H 2 O 2 is reported. Through the reaction of formaldehyde with the amino moieties (–NH 2 ) on the g ‐C 3 N 4 surface, N ‐hydroxymethyls groups (‐NH‐CH 2 ‐OH) are introduced on typical g ‐C 3 N 4 photocatalysts. Relative to the pristine g ‐C 3 N 4 photocatalysts, the modified g ‐C 3 N 4 photocatalysts have over 1280% higher activity for H 2 O 2 production in pure water system, and impressive solar‐to‐chemical conversion efficiency. The experimental investigations and theoretical calculations reveal that the introduction of ‐NH‐CH 2 ‐OH on the g ‐C 3 N 4 photocatalysts does not change their morphology, light absorption intensity and edges, band positions, charge separation and transfer properties, but markedly improved the H 2 O dehydrogenation and O 2 adsorption properties of g ‐C 3 N 4 . As a result, the reduction kinetics of O 2 to H 2 O 2 on the g ‐C 3 N 4 photocatalysts with ‐NH‐CH 2 ‐OH is more energetically favorable. This work provides a useful reference and inspiration to achieve the effective modification of g ‐C 3 N 4 or other metal‐free photocatalysts from the kinetic perspective.