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 hydrogen evolution reaction (HER) due to its facile synthesis, outstanding chemical/thermal stability and suitable band structure. However, the unsatisfactory performance of pristine g-C3N4 severely restricts its its further widespread application. 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 (ΔGH*) of g-C3N4 to near zero. Inspired by the theoretical predictions, an advanced HER photocatalyst of sulfur-doped g-C3N4/V2C MXene (SCN/V2C) Schottky junction is fabricated successfully by vacuum ball milling and subsequent annealing treatment. Interface-charge transfer between SCN and V2C endows a strong electron interaction, which not only improves hydrophilicity and visible-light absorption, but also facilitates the separation and migration of photoexcited carriers. Density functional theory calculations and in situ characterization results corroborate that the carrier migration of SCN/V2C adheres to the typical Schottky heterojunction mechanism. Femtosecond transientabsorption (fs-TA) spectroscopy demonstrates the favorable carrier dynamic behavior of developed SCN/V2C photocatalysts. Thus, the SCN/V2C achieves a superior H2 production rate of 8003 μmol g-1 h-1. The Schottky heterojunction established in this research provides valuable insights into the further strategic design and construction of high-performance HER photocatalysts.