Currently, the most efficient Sb2Se3 solar cells have been achieved in superstrate configuration using a chemical bath deposition approach. With selenourea as an additive, the Sb2Se3 planar solar cells delivered a benchmark PCE of 10.57%. In 2021, Chen et al. developed a hydrothermal approach for superstrate Sb2Se3 solar cells, reaching a PCE of 7.9%. However, there has been relatively little attention on the hydrothermal synthesis of substrate-based Sb2Se3 solar cells and Sb2Se3 photocathodes for PEC water splitting, possibly because of challenges in nucleation on the substrate. Given the benchmark achievement in Sb2Se3 solar cells using a solution-processed strategy, developing a hydrothermal method for synthesizing substratebased Sb2Se3 photocathodes becomes imperative.