Enhancing stability and PEC performance of TiO2 for Bias-Free seawater splitting with an FeS layer and In-Situ FeOOH Regeneration

Abstract

Photoelectrochemical (PEC) seawater splitting is a promising technology for renewable energy production. However, the photoanodes and photocathodes of PEC system faces challenges such as poor stability and low performance. In this study, a regenerable and highly stable TiO₂/FeS/FeOOH photoanode was designed for PEC seawater splitting. The integration of p-type FeS formed a p-n heterojunction, improving the photogenerated carrier transfer. The FeOOH layer, formed by the electrochemical oxidation of FeS, serves as a dense co-catalyst protective layer, protecting the photoanode from seawater corrosion. Notably, the FeS material can continuously supply FeOOH through a simple in-situ electrochemical oxidation process, compensating for FeOOH consumption and making the photoanodes regenerable, thereby significantly extending their stability. The optimal TiO₂/FeS/FeOOH achieved a photocurrent density of 2.08 mA/cm² at 1.23 V_RHE and an STH efficiency of 1.353 % in a bias-free tandem PEC seawater splitting cell. Assisted by the regenerable of FeOOH, the photoanode maintained 94.2 % of its performance after a 200-hour reaction. This study provides valuable insights for the development of PEC cells based on TiO₂ materials for bias-free seawater splitting.