Synergistic effect of surface modification and effective interfacial charge transfer over faceted g-C3N4/ZnSe heterojunction to enhance CO2 photoreduction activity

Abstract

Heterojunction and surface modification are promising methods to boost the photocatalytic CO2 conversion efficiency which help to optimize the redox ability of photocatalysts and enhance the separation efficiency of photogenerated charge carriers. Herein, a novel surface-modified and interfacial heterojunction of g-C3N4 (CN) over a faceted ZnSe (ZS) {CN/ZS} composite was developed to accelerate the transfer of photogenerated electrons (e−) and holes (h+) between the CN and ZS photocatalysts. This technology allows faster transfer of a larger quantity of excited reductive electrons to the surface of ZS with a lower CO2 adsorption energy. Based on photocatalytic CO2 reduction to CO and CH4, 3 mmol CN/ZS composite outperformed all as-prepared photocatalysts including pure CN and ZS, with yielding rates of 439 and 203 umolg−1, respectively, with 88 % CO2 selectivity. The improved photocatalytic activity and selectivity were attributed to enhanced visible-light absorption, improved CO2 activation and adsorption on the surface of the photocatalyst and facilitated charge transfer at the interface. This study offers a novel approach for precisely controlling the direction of photogenerated charge separation by constructing a heterostructure for CO2 photoreduction.