Edge functionalization of terminal amino group in carbon nitride by in-situ C–N coupling for photoreforming of biomass into H2

Abstract

Solar-driven water splitting is a promising approach for H2 generation, but in order to accelerate the reaction rate, high-cost sacrificial agents are usually required. Photoreforming of biomass serves as an alternative strategy for sustainable H2 generation. Carbon nitride has recently emerged as a promising photocatalyst for the photorefoming reaction, however its performance is largely hindered by its poor visible light absorption. Here, we report, for the first time, the fabrication of an edge functionalized carbon nitride with remarkable visible light absorption via an in-situ C–N coupling method. By using N-acetylethanolamine (NA) as an additive to react with the precursors including urea, dicyandiamide, and melamine, the ethyl alcohol groups are grafted to the heptazine rings by replacing the terminal amino groups. Experimental results and DFT calculations reveal that the introduction of ethyl alcohol group leads to the generation of a new discrete energy level in the bandgap, resulting in significant increase in visible light absorption. The ethyl alcohol group herein serves as an electron donor, which would modulate the electron distribution to form an internal electric field to improve the charge separation. Moreover, the presence of ethyl alcohol group could favor the absorption of the biomass entity. The tuned CN shows superior photoreforming performance compared to the pristine CN in the presence of proton reduction Pt cocatalysts. It allows for visible-light-driven conversion of several monosaccharides into H2 without the need for sacrificial agents.