Alleviating Charge Recombination Caused by Unfavorable interaction of P and Sn in Hematite for Photoelectrochemical Water Oxidation

Hematite (Fe2O3) is a promising photoanode for photoelectrochemical (PEC) water splitting, yet its performance is hindered by low electrical conductivity and charge recombination. Phosphorus (P) doping into hematite has been highlighted for its potential to enhance conductivity and minimize recombination by preventing electron trapping through P5+ states. Despite the interest in P doping to improve hematite photoanodes, establishing an effective P-doping synthesis remains challenging, often resulting in suboptimal PEC outcomes. In this study, we identify that unintentional tin (Sn) diffusion from the fluorine-doped tin oxide (FTO) substrate significantly impacts P-doped Fe2O3 performance. Addressing the detrimental interaction between unintentional Sn4+ and intentional P5+ dopants, we introduce titanium (Ti) as a guest dopant to mitigate dopant repulsion. The resulting P:Sn:Ti–Fe2O3 exhibits a 4-fold increase in photocurrent density to 3.44 mA cm–2 at 1.23 VRHE, marking a significant advancement in P-doped hematite research. With a NiFeOx cocatalyst, the NiFeOx/P:Sn:Ti–Fe2O3 photoanode further reaches a peak photocurrent density of 4.30 mA cm–2 at 1.23 VRHE. Our findings, both experimental and computational, demonstrate that overcoming negative dopant interactions is crucial for enhancing PEC performance and ensuring the photoanode's thermodynamic stability.