Bandgap Reduction and Enhanced Photoelectrochemical Water Electrolysis of Sulfur-doped CuBi2O4 Photocathode

As interest in hydrogen energy grows, eco-friendly methods of producing hydrogen are being explored. CuBi2O4 is one of the p-type semiconductor cathode materials that can be used for photoelectrochemical hydrogen production via environment-friendly water electrolysis. CuBi2O4 has a bandgap of 1.5 - 1.8 eV which allows it to photogenerate electrons and holes from the absorption of visible light. This study investigated the effect of sulfur doping on the bandgap and photoelectrochemical water reduction properties of CuBi2O4. Sulfur-doped CuBi2O4 thin films were electrochemically synthesized using a nitrate-based precursor solution with thiourea. This was followed by two-step annealing in an Ar atmosphere, which effectively prevented the oxidation of sulfur. Sulfur doping up to 0.1 at% led to the expansion of the lattice volume of the v. The bandgap was reduced from 1.9 eV to 1.5 eV with increasing doping concentration, which resulted in the enhancement of photoelectrochemical current density by similar to 240%. X-ray photoelectron spectroscopy showed that sulfur-doping reduced oxygen vacancies with increasing doping concentration, confirming that the enhanced photoelectrochemical properties resulted from the reduction in bandgap, not from any extrinsic factor such as oxygen vacancies. Further studies of sulfur-doped CuBi2O4 to improve surface coverage are expected to lead to a more promising photoelectrochemical cathode material.

Automated summary

As interest in hydrogen energy grows, eco-friendly methods of producing hydrogen are being explored. CuBi2O4, a p-type semiconductor cathode material, has been investigated for its potential in photoelectrochemical hydrogen production. This study focused on the effect of sulfur doping on the bandgap and photoelectrochemical water reduction properties of CuBi2O4. The results showed that sulfur doping led to an expansion of the lattice volume, reduction in bandgap, and enhancement of photoelectrochemical current density. Further studies are expected to improve the surface coverage of sulfur-doped CuBi2O4 and optimize its performance as a photoelectrochemical cathode material.