Borate modified α-Fe₂O₃ achieves efficient photocatalytic water splitting for hydrogen production

H₂, as an efficient and clean energy source, possesses advantages such as high calorific value (285.8 kJ/mol), cleanliness, and wide availability, making it one of the most promising alternatives to fossil fuels. Under the global push for low-carbon energy policies, photoelectrocatalytic water splitting using photoelectrochemical cells has emerged as a promising and environmentally sustainable method for hydrogen production. A critical step in this process is the preparation of cost-effective and stable semiconductor catalysts. As a photoanode, α-Fe₂O₃ has high theoretical photoelectric conversion efficiency and stability, but it also has drawbacks such as poor conductivity, short hole diffusion length and excitons. In order to improve its photoelectric performance, an ultrathin amorphous borate cocatalyst (BC) layer was deposited on the surface of the α-Fe₂O₃ nanorod array using a dip-coating and annealing method, resulting in the BC/α-Fe₂O₃ photoanode catalyst for photoelectrocatalytic water splitting to produce hydrogen. Subsequently, the composition, morphology, surface state, spectral absorption characteristics, and molecular valence forms of the photoanode catalyst were analyzed. The impact of different preparation and loading conditions of the BC on the photoelectric performance was tested and compared, and the role of BC in the photoelectrocatalytic water splitting process was investigated. The research results indicated that the loading of the BC significantly reduced the trap density and oxygen evolution overpotential on the surface of the α-Fe₂O₃ nanorod array, thereby improving charge separation efficiency and enhancing the photoelectrocatalytic activity of the photoanode. Under conditions of 100 mW/cm² light intensity, 0.1 mol/L KOH solution, and an applied bias of 1.23 V (relative to the reversible hydrogen electrode), the BC/α-Fe₂O₃ photoanode achieves a photocurrent density of 1.50 mW/cm², with a monochromatic light conversion efficiency of 26% (λ=360 nm).