Revealing improved electrocatalytic performances of electrochemically synthesized S and Ni doped Fe₂O₃ nanostructure interfaces

Non-precious-metal oxides provide various physical and chemical controllable properties when their composition and morphology are tuned for electrochemical applications. However, the unstable features due to catalytic degradation caused by the dissolution and agglomeration of the materials in acidic media have prevented the widespread use of these materials in electrocatalysis. We propose a facile and simple method for the synthesis of S and Ni co-doped single-crystal-like iron oxide nanorods (S,Ni_Fe₂O₃ NR) grown over a MoS₂ substrate. The S,Ni_Fe₂O₃ NR catalyst demonstrated a stable current density of nearly −100 mA/cm² when operated at a constant potential of −0.31 V (vs. SHE) without structural and chemical deformation of the material. The commercial Fe₂O₃ showed agglomerated particles after a stability test. In addition, the newly prepared S,Ni_Fe₂O₃ NR catalyst exhibited excellent catalytic HER performance with an overpotential of −92 mV (vs. SHE) to reach −10 mA/cm² (a Tafel slope of 54 mV/dec). Our density functional theory (DFT) calculations suggest that a heterogeneously mixed surface with Ni and S atoms on the Fe₂O₃ surface can improve the HER performance. This work provides information about the design and development of future electrocatalysts with non-precious-metal oxides for use in an acidic environment.