Metal-free tellurene cocatalyst with tunable bandgap for enhanced photocatalytic hydrogen production

The discovery of metal-free elemental cocatalysts has spurred dramatic advances in the field of photocatalysis. Bandgap engineering has always been used as an effective approach to make these cocatalysts form favorable band alignment with photocatalysts. Here, we develop metal-free tellurene (Te) with largely tunable bandgap as a highly efficient cocatalyst and investigate its thickness-dependent catalytic activity. Our experimental and theoretical studies reveal that the increased reduction potential of conduction band together with the decreased thickness, abundant active sites, and high charge mobility of Te, as well as the strong electronic coupling effects between Te and metal sulfides enable the enhanced photocatalytic hydrogen evolution rate and high quantum efficiency of 11.4% under the light illumination with the wavelength of 420 nm. This work enriches our understanding of the structure–activity correlations for Te and opens a path for solar energy harvesting from artificial photosynthesis by robust and cost-effective photocatalysts.