Discharging antibonding orbital electrons of 1T-MoS2 by S-rich treatment for promoting photocatalytic H2 evolution

Abstract

Compared with thermodynamically stable hexagonal MoS₂ with semiconducting 2H phases (2H-MoS₂), metastable trigonal and metallic 1T-MoS₂ as a photocatalytic H₂-evolution cocatalyst exhibits higher electronic conductivity and more available active S atoms. However, the S–H_ads bond of 1T-MoS₂ is still relatively weak, which is not beneficial to H adsorption for the interfacial H₂-production reaction. To greatly enhance the H-adsorption ability of S sites in 1T-MoS₂, in this paper, a H-adsorption regulation strategy by discharging antibonding orbital electrons is proposed to construct an S-enriched 1T-MoS₂ cocatalyst (denoted as 1T-MoS_2+x). Herein, the 1T-MoS_2+x cocatalyst was first synthesized by a hydrazine hydrate-assisted one-step hydrothermal route and was then modified on a TiO₂ surface via an ultrasound-assisted method to prepare a 1T-MoS_2+x/TiO₂ photocatalyst. Photocatalytic performance tests showed that the 1T-MoS_2+x/TiO₂ (5%) sample displayed optimal H₂-evolution activity, which was 162.4, 15.3, and 5.1 times higher than that of TiO₂, 2H-MoS₂/TiO₂ (5%), and 1T-MoS₂/TiO₂ (5%), respectively. A series of DFT calculations and characterization uncover that the enrichment of S in 1T-MoS_2+x can induce electron redistribution to produce electron-deficient S^(2−δ)−, leading to decreased antibonding-orbital occupancy, which increases the stability of S–H_ads bonds and enhances the H-adsorption ability of S sites for rapid H₂ production. This study proposes a fresh idea to increase the active-site efficiency of MoS₂-based cocatalysts by the reasonable regulation of antibonding orbital occupation.