Interfacial engineering enabling solution-processed Cu:NiOx/Sb2Se3/TiO2/Pt photocathodes for highly efficient photoelectrochemical water-splitting†

Sb₂Se₃ is a promising photocathode with good stability and large theoretical photocurrent density but suffers from severe recombination of electron–hole pairs at the interface, which greatly limits its application in photoelectrochemistry. To tackle this issue, heterostructured photoelectrodes with efficient cocatalysts should be rationally designed and fabricated, which are usually made by expensive and complicated atomic layer deposition methods (ALD). Herein, a facile chemical bath deposition (CBD) method is proposed to construct heterostructured photocathodes composed of TiO₂ and Sb₂Se₃, as well as to deposit a cocatalyst of Pt nanoparticles (NPs) on the photoelectrode. The TiO₂ layer could protect Sb₂Se₃ and also capture the photogenerated electrons produced by Sb₂Se₃, and then improve charge separation. Pt is utilized as a co-catalyst to enhance the carrier injection efficiency and hence accelerate the surface hydrogen evolution reaction. Under simulated sunlight conditions, Sb₂Se₃-5/TiO₂-3/Pt-6 with the optimized configuration exhibited a flat band potential of 0.52 V_RHE, which is positively shifted by 0.09 V with respect to that of bare Sb₂Se₃. Notably, photocurrent densities of −1.0 mA cm⁻² at −0.2 V_RHE and 0.56 mA cm⁻² at 0 V_RHE were achieved. This represented 12.5 and 7 times improvement in photocurrent densities compared to bare Sb₂Se₃ NPs. Our study provides a facile and effective method for the interface engineering of Sb₂Se₃, resulting in a significant enhancement of its photoelectrochemical activity for serving as a high-performance photocathode for solar water splitting.