S-doped FeOx for high-efficiency hydrogen production from thermocatalytic water splitting

Thermocatalytic water splitting to produce hydrogen at low temperature was of great significance. In this study, a series of efficient and stable FeO x and FeO x S x catalysts were synthesized via a liquid precipitation method using ferrous sulfate, sodium hydroxide, and thiourea as precursors. The study focused on investigating the effects of sulfur introduction and preparation atmosphere on the catalytic performance. These catalysts were characterized by SEM, XRD, FT-IR, XPS and H 2 -TPR, which confirmed the successful preparation of sulfur-doped catalysts (denoted as FeO x S x -Air and FeO x S x -O 2 ). Under reaction conditions of 350 °C and water vapor (space velocity: 0.3 mL min −1 ), the sulfur-doped catalysts demonstrated superior activity, with FeO x S x -Air and FeO x S x -O 2 achieving H 2 production rates of approximately 0.0523 mmol (mL g) −1 and 0.04092 mmol (mL g) −1 , respectively, outperforming their undoped counterparts (FeO x -Air and FeO x -O 2 ). Meanwhile, FeO x S x -Air with the higher activity was more beneficial for the reaction than FeO x S x -O 2 , which indicated that a lower oxygen partial pressure facilitated the formation of unsaturated Fe coordination environments. The performance enhancement was attributed to the synergistic effect of sulfur doping and low oxygen partial pressure, which optimized the Fe 2+ /Fe 3+ ratio and accelerated the Fe + /Fe 3+ redox cycle, thereby improving charge transfer efficiency and optimizing hydrogen production. These findings highlighted the critical role of sulfur incorporation under low-oxygen conditions in boosting the catalytic activity of iron oxide-based for low-temperature water splitting.