Accelerating photogenerated charge kinetics via the g-C3N4 Schottky junction for enhanced visible-light-driven CO2 reduction

Abstract

In the construction of metal-semiconductor heterojunction, rationally tuning the Schottky barrier has a significant influence on its catalytic activity. Herein, we have successfully constructed plasmonic Ag NPs on nitrogen-vacancy modified g-C3N4 nanotubes (ACNNT) through a facile in situ self-assembly strategy for realizing high visible-light photocatalytic CO2 conversion. Benefiting from uniform distribution of Ag NPs and spatially directed separation and migration of 1D tubular g-C3N4 architecture, the plasmonic metal utilization efficiency can be significantly enhanced. The ACNNT catalyst exhibits a superior CO evolution rate of 88.2 μmol g−1 h−1 under visible light irradiation, more than 10.9 times higher than BCN. DFT calculations combined with experimental studies demonstrate that the introduced nitrogen vacancy can alter the Schottky barrier at the interface and simultaneously diminish the energy barrier for CO2 activation. Therefore, the optimized Schottky barrier height not only accelerate charge kinetics via the driving force from the Schottky junction, but also prevent the photoelectrons trapped by Ag from flowing back to g-C3N4 under visible light, which effectively inhibit the photoinduced charge carrier recombination, thus contributing to more efficient CO2 photoreduction. This work reveals a key insight on the construction of carbon nitride-based Schottky heterojunction in the field of photocatalytic CO2 reduction.