Heterogeneous engineering of nickel-iron sulfide with cerium-promoted reconstruction for enhanced oxygen evolution

The development of efficient oxygen evolution reaction (OER) electrocatalysts is critical for electrochemical water splitting. Herein, a cerium-doped Ni3S2/NiS/FeS heterogeneous structure nanoparticle supported on nickel foam (Ce-NiSx/FeS/NF) is prepared as a precatalyst for OER reaction in alkaline solution. The heterointerfaces of NiSx/FeS adjust the electronic structure and expose more active sites, accelerating the OER process. The Ce incorporation promotes the in situ reconstruction and oxidation of the sulfides to the heterogeneous NiOOH/FeOOH, which act as the actual active sites for the OER reaction. Thus, the Ce-NiSx/FeS/NF demonstrates excellent OER performance with a low overpotential of 125 mV at 10 mA cm−2 and long-term robustness. Additionally, a water splitting device is constructed using Ce-NiSx/FeS/NF and commercial Pt/C/NF as the anode and cathode, respectively. This device achieves a current density of 10 mA cm−2 at 1.38 V with 50 h of reliable continuous operation at 1.78 V. Density functional theory (DFT) calculation confirms that the active sites of Ce-NiOOH/FeOOH optimize intermediates adsorption energy (higher OH− adsorption energy and lower O2 desorption energy) and provide faster OER kinetics, conducive to the OER process. This work presents the concept of rare-earth-doping promotes reconstruction of heterogeneous transition-metal-based compounds for the development of high-performing OER electrocatalysts.