Enhancing photocatalytic hydrogen evolution using a novel heterojunction

A research paper titled Interfacial linkage modulated amorphous molybdenum sulfide/bismuth halide perovskite heterojunction for enhanced visible-light-driven photocatalytic hydrogen evolution has been published in the Applied Catalysis B: Environment and Energy by researchers He Zhao, Rossella Greco, Rafal Sliz, Olli Pitkänen, Krisztian Kordas, and Satu Ojala.

This research article focuses on enhancing photocatalytic hydrogen evolution using a novel heterojunction. The study introduces a strategy to tailor the interface of hybrid tri(dimethylammonium) hexaiodobismuthate (DMA3BiI6) and amorphous molybdenum sulfide (a-MoSx) heterojunctions. The key innovation lies in creating an interfacial Mo–S–Bi linkage, which promotes efficient charge transfer. The resulting heterostructures demonstrate improved visible-light-driven photocatalytic hydrogen evolution, achieving a high hydrogen evolution rate and quantum efficiency. The authors conduct detailed physicochemical characterization and photoelectrochemical experiments to elucidate the charge transfer mechanisms and demonstrate long-term stability. Ultimately, the findings suggest a promising approach to improve the photocatalytic performance of bismuth halide perovskite-based systems for solar-to-fuel conversion.

The Timegate PicoRaman instrument using Timegated® Technology was utilized to analyze the structure of amorphous molybdenum sulfide (a-MoSx). This analysis revealed several vibration bands, with peaks at 380 and 403 cm-1 corresponding to the vibrational modes of a particular form of molybdenum sulfide (2H-MoS2). These modes were broadened in a-MoSx, indicating defects such as sulfur vacancies. Additional peaks related to the distorted lattice of a-MoSx were also identified. The shift of one peak to a lower value suggested a weakening of molybdenum-sulfur bonds due to sulfur vacancies, further supported by another broad peak, leading to the conclusion that a-MoSx consists of disordered 2H-MoS2 with sulfur vacancies. Based on the analysis of the Raman spectra, it was presumed that the a-MoSx consists of disordered 2 H–MoS2 with S vacancies. 

Read more from the open-access article here.

Abstract

Photocatalytic hydrogen evolution is a promising approach for direct solar-to-fuel conversion. Although significant research efforts have been put on the development of lead-free metal halide perovskites to reach excellent optoelectronic properties, their rational design for efficient heterojunction photocatalytic systems still poses challenges. Here, we report a new strategy to tailor the interface of hybrid tri(dimethylammonium) hexaiodobismuthate (DMA₃BiI₆) and amorphous molybdenum sulfide (a-MoS_x) heterojunctions. Specifically, a-MoS_x was prepared with abundant apical S^2– or bridging S₂^2– ligands to allow coupling with DMA₃BiI₆ via an interfacial Mo–S–Bi linkage. The as-obtained heterostructures were found to show an improved visible-light-driven photocatalytic hydrogen evolution in hydroiodic acid splitting under mild conditions reaching a superior hydrogen evolution rate of around 750 µmol g⁻¹ h⁻¹ and an apparent quantum efficiency (AQE) of 13.0 % at 420 nm. The high activity was kept after a long-term performance test for 3 days.

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