Superimposing effect of electrocatalytic activity and photocatalytic activity for amorphous NiFe-sulfides photoanode in sulfion oxidation reaction

Crystalline transition metal (TM) sulfides exhibit metallic behavior and have been identified as ideal electrocatalytic candidates for electrochemical sulfion oxidation reaction (SOR). However, the SOR performance for amorphous TM sulfides is still poorly understood so far. Herein, we sulfurized NiFeOOH clusters deposited on ZnIn₂S₄ nanosheets arrays to amorphous NiFe-based sulfides (denoted as NiFeS) for photoelectrochemical SOR. We found amorphous NiFeS presented a n-type semiconductor property, the elaborate band alignment between NiFeS band gap structure and the oxidation potential of S²⁻ promoted the superimposing effect of electrocatalytic and photocatalytic current for SOR under illumination. The overall SOR current density of ZnIn₂S₄/NiFeS reaches the maximum value about 7.6 mA cm⁻² at 0.6 V vs. RHE after 6 h stability test, which was composed by 2.6 mA cm⁻² electrocatalytic current density and 5.0 mA cm⁻² photocatalytic current density. Our work presents a new strategy for sulfion oxidation reaction based on amorphous transition metal sulfides.