Sulfur-doped g-C3N4/V2C MXene Schottky junctions for superior photocatalytic H2 evolution†

Abstract

Graphitic carbon nitride (g-C₃N₄) is considered to be a promising photocatalyst for the hydrogen evolution reaction (HER). However, the photocatalytic HER performance of pristine g-C₃N₄ is unsatisfactory. In this work, theoretical predictions reveal that integrating sulfur dopants and coupling vanadium carbide (V₂C) MXene can significantly optimize the hydrogen adsorbed Gibbs free energy (ΔG_H*) of g-C₃N₄ to near zero. Inspired by the theoretical predictions, a sulfur-doped g-C₃N₄/V₂C MXene (SCN/V₂C) Schottky junction photocatalyst is fabricated by vacuum ball milling and subsequent annealing treatment. The strong SCN–V₂C interface-electron interaction not only improves hydrophilicity and light absorption, but also facilitates the separation and migration of photoexcited carriers. Density functional theory calculations and the in situ characterization results corroborate that the carrier migration of SCN/V₂C adheres to the typical Schottky heterojunction mechanism. Femtosecond transient absorption (fs-TA) spectroscopy demonstrates the favorable carrier dynamic behavior of SCN/V₂C. Thus, SCN/V₂C achieves a superior H₂ production rate of 8003 μmol g⁻¹ h⁻¹. This research provides valuable insights into the further strategic design and construction of high-performance Schottky heterojunction catalysts.