Boosting O2 Reduction and H2O Dehydrogenation Kinetics: Surface N-Hydroxymethylation of g-C3N4 Photocatalysts for the Efficient Production of H2O2

g-C3N4 photocatalysis is a safe and green approach for H2O2 production, but the activity of pristine g-C3N4 photocatalysts is unsatisfactory. At present, most of the modifications on g-C3N4 photocatalysts for H2O2 production have focused on thermodynamic processes, few have considered the kinetic aspects. Herein, the surface N-hydroxymethylation of g-C3N4 photocatalysts for the efficient kinetic production of H2O2 is reported. Through the reaction of formaldehyde with the amino moieties (-NH2) on the g-C3N4 surface, N-hydroxymethyls groups (-NH-CH2-OH) are introduced on typical g-C3N4 photocatalysts. Relative to the pristine g-C3N4 photocatalysts, the modified g-C3N4 photocatalysts have over 1280% higher activity for H2O2 production in pure water system, and impressive solar-to-chemical conversion efficiency. The experimental investigations and theoretical calculations reveal that the introduction of -NH-CH2-OH on the g-C3N4 photocatalysts does not change their morphology, light absorption intensity and edges, band positions, charge separation and transfer properties, but markedly improved the H2O dehydrogenation and O-2 adsorption properties of g-C3N4. As a result, the reduction kinetics of O-2 to H2O2 on the g-C3N4 photocatalysts with -NH-CH2-OH is more energetically favorable. This work provides a useful reference and inspiration to achieve the effective modification of g-C3N4 or other metal-free photocatalysts from the kinetic perspective.

Automated summary

The study focuses on surface modification of g-C3N4 photocatalysts for efficient production of H2O2. The modified photocatalysts show over 1280% higher activity compared to pristine ones in pure water system, with impressive solar-to-chemical conversion efficiency. The introduction of -NH-CH2-OH on the g-C3N4 photocatalysts improves the H2O dehydrogenation and O-2 adsorption properties, making the reduction kinetics of O-2 to H2O2 more energetically favorable.