Viologen Doping Induced Charge Storage of Carbon Nitride for Enhanced Photocatalytic Hydrogen Production

Abstract

The rapid recombination of photogenerated charges is the primary bottleneck hindering the photocatalytic hydrogen generation with graphitic carbon nitride (g-C3N4). Herein, by introducing methyl viologen (MV) into the carbon nitride framework, CN-MV-x with enhanced photoinduced charge carriers separation is fabricated. The surface chemistry and photoelectrochemical properties of the CN-MV-x samples are greatly enhanced. Due to the increased charge separation with the electron extraction by doped MV, the highest hydrogen evolution rate of 1.65 mmol/g/h is achieved by the CN-MV-x photocatalyst doped with 10 mmol MV (CN-MV-10). More impressively, the CN-MV-10 also shows an extraordinary electron storage ability, which powers the time-delayed hydrogen production in the dark after light illumination. Further analysis indicates that this time-delayed hydrogen evolution ability ascribed to the electron accumulation in the conduction band of carbon nitride. This study provides a new route to improve the photoinduced charge separation by introducing redox species.