N-doped rutile TiO2 nanorod@g-C3N4 core/shell S-scheme heterojunctions for boosting CO2 photoreduction activity

Abstract

The design of heterojunction photocatalysts is regarded as a very effective method to solve the high recombination rate of photogenerated charge carriers for CO₂ photoreduction into hydrocarbons, and interface engineering is urgently required to achieve high efficiency. Herein, graphitic carbon nitride (g-C₃N₄, CN) was uniformly grown on the surface of nitrogen-doped rutile TiO₂ (NT) nanorods by in situ deposition, and a NT@CN core/shell step-scheme (S-scheme) heterojunction system composed of NT nanorods and g-C₃N₄ was synthesised. The as-synthesised heterojunction containing 55 wt% g-C₃N₄ delivered the highest CO₂ photoreduction activity (33.35 μmol g⁻¹ for CO) without additional cocatalysts or external sacrificial agents, which was 7.1 times higher than that of bare NT nanorods. This improved CO₂ reduction activity was attributable to the large surface area and impactful S-scheme heterostructure, which imparted the catalyst with sufficient visible-light harvesting ability, promoted the segregation and transformation of the photoinduced charge pairs, and enhanced the redox ability of the carriers. Concurrently, the NT@CN photocatalyst exhibited excellent reusability and stability. This work offers a new basis for designing and preparing rutile TiO₂-based S-scheme heterojunctions with enhanced CO₂ reduction performance.