Acid–base resistant ligand-modified molybdenum–sulfur clusters with enhanced photocatalytic activity towards hydrogen evolution

Abstract

Studying the active sites associated with the hydrogen evolution reaction (HER) in molecular detail is challenging, but critical to the development of a high-performance catalyst for the generation of H₂, a carbon-free fuel derived from water. We report a well-defined molecule, Mo^IV₃S₇(MBTZ)₃Br (MoS-MBTZ, where MBTZ = 2-mercaptobenzothiazole), which has a triangular fragment of molybdenum disulfide (MoS₂). MoS-MBTZ displays excellent acid–base stability and survives for at least one month in solution at pH 1–14. Notably, the complex exhibits superior activity as a heterogeneous photocatalyst for the HER, producing H₂ at a rate of 101.81 mmol g⁻¹ h⁻¹, which is 16.3 and 188.5 times that of the organic ligand-free cluster (NEt₄)₂Mo^IV₃S₇Br₆ (MoS-Br) and commercial MoS₂ under visible light irradiation (λ ≥ 420 nm), respectively. Experimental results and theoretical calculations show that the edge and even the face sites of S atoms of the trimeric Mo–S units are activated significantly by coordination with MBTZ, as a result of the effect of MBTZ on the energy band structure and the facilitated separation and transfer of photogenerated carriers. This work provides a structurally precise model with which to explore the impact of an organic ligand on the photocatalytic HER activity and to reveal the structure–property relationships.