Improving Silicon Photocathode Performance for Water Reduction through Dual Interface Engineering and Integrating ReS₂ Photocatalyst

Photoelectrochemical (PEC) water splitting for H₂ production is a possible alternative for fossil energy in the future. However, there exists three problems in PEC water splitting with the silicon (Si) photocathode: poor light absorption of the untreated Si substrate, bad stability in strong acid solution, and poor photocatalytic activity of Si. Here, a strategy of dual interface engineering and photocatalyst deposition is proposed to improve the PEC performance, which consists of fabricating black Si (b-Si) by reactive ion etching, depositing of TiO₂ on the b-Si by atomic layer deposition, and growing ReS₂ on top of the TiO₂ by chemical vapor deposition. Owing to the suitable band alignment of b-Si, TiO₂, and ReS₂, the ReS₂/TiO₂/b-Si shows obviously enhanced PEC performance compared to b-Si, TiO₂/b-Si, and ReS₂/b-Si photocathodes. Results of electrochemical impedance spectroscopy and Mott–Schottky plot analysis demonstrate that the TiO₂ layer plays an important role and the charge-transfer kinetics of the system is clearly improved. Transient photocurrent measurements indicate that the ReS₂/TiO₂/b-Si photocathode has the most remarkable photocurrent response. In addition, the ReS₂/TiO₂/b-Si photocathode also shows excellent stability after being operated for 25 h.