The controlled synthesis of nitrogen and iron co-doped Ni3S2@NiP2 heterostructures for the oxygen evolution reaction and urea oxidation reaction.

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At present, global resources are nearly exhausted and environmental pollution is becoming more and more serious, so it is urgent to develop efficient catalysts for hydrogen production. Herein, nitrogen and iron co-doped Ni3S2 and NiP2 heterostructures with high efficiency oxygen evolution reaction (OER) and urea oxidation reaction (UOR) performances were firstly successfully prepared on nickel foam by hydrothermal and high-temperature calcination methods. Benefiting from the hierarchical structure, the exposure of more active sites and the doping effect of N and Fe, the N-Fe-Ni3S2@NiP2/NF material showed excellent electrocatalytic activity for the OER and UOR. The N-Fe-Ni3S2@NiP2/NF material displays excellent catalytic OER performance; the overpotential is only 251 mV to drive 100 mA cm-2 current density, while for the UOR, the potential is only 1.353 V to drive 100 mA cm-2 current density, which is one of the best catalytic activities reported so far. It is worth noting that scanning electron microscopy showed that the surface of N-Fe-Ni3S2@NiP2/NF is rough and has some mesopores, which may have resulted in an increase of active sites during the electrocatalytic process. The N-Fe-Ni3S2@NiP2/NF electrode couple also has relatively long-term durability in alkaline solutions, maintaining a stable current density for 15 h at 1.35 V. The density functional theory (DFT) calculation shows that the in situ generated Fe doped nanooxides exhibit strong water adsorption energy, which may be one of the reasons for the good catalytic activity. Our work is conducive to the rational design of electrocatalysts for efficient hydrogen production from water splitting and wastewater treatment.