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

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-C 3 N 4 nanotubes (ACNNT) through a facile in situ self-assembly strategy for realizing high visible-light photocatalytic CO 2 conversion. Benefiting from uniform distribution of Ag NPs and spatially directed separation and migration of 1D tubular g-C 3 N 4 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 CO 2 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-C 3 N 4 under visible light, which effectively inhibit the photoinduced charge carrier recombination, thus contributing to more efficient CO 2 photoreduction. This work reveals a key insight on the construction of carbon nitride-based Schottky heterojunction in the field of photocatalytic CO 2 reduction. • A Schottky junction photocatalyst composed of Ag and nitrogen vacancy-g-C 3 N 4 nanotube is synthesized. • The optimized Schottky barrier accelerates charge kinetics, suppress backward transfer of electrons. • ACNNT exhibits a CO evolution rate of 88.2 μmol g -1 h -1 under visible light irradiation. • Ag active centers with accumulated electrons diminish the energy barrier for CO 2 activation.