Efficient photothermal conversion and Z-scheme charge transfer in narrow-gap semiconductor heterojunction for photothermal-assisted photocatalysis

The design of semiconductors with excellent charge separation and photothermal conversion efficiency is crucial for solar-driven photocatalytic hydrogen production. Herein, a narrow-bandgap semiconductor junction by growing Bi2S3nanosheets on ReS2nanoflowers is designed for efficient photothermal-assisted photocatalytic hydrogen generation. The Bi2S3/ReS2hybrids featuring a distinctive 3D flower-like morphology and 2D/2D heterointerfaces are prepared via a handy method. The synergistic excitations of the narrow bandgaps endow these hybrids with a broad light absorption spectrum, ranging from the ultraviolet to the near-infrared region. Additionally, the Bi2S3/ReS2hybrids demonstrate superior photothermal conversion in both solution and solid states, originating from the efficient light absorption and nonradiative relaxation of lattice thermal vibrations. The well-matched band alignment of the two narrow-bandgap semiconductors confers upon the hybrids a built-in electric field and a Z-scheme charge-transfer pathway, significantly enhancing charge separation and suppressing the charge recombination. Under simulated solar light irradiation, the ReS2/Bi2S3hybrids exhibit a substantially enhanced photocatalytic hydrogen generation rate, which is 38.5 times and 7.36 times that of ReS2and Bi2S3, respectively. Temperature-dependent photocatalytic experiments reveal that the hybrids’ excellent photothermal conversion contributes to about a 23 % improvement on photocatalysis compared to that tested at low temperature. This improvement is attributed to the local temperature rise, which further enhances charge transfer efficiency and the hydrogen reduction reaction. This study offers an inspiration for the design of photocatalysts based on narrow-bandgap semiconductors for photothermal-assisted photocatalysis.