Rational modulation of interfacial electronic structure in Ni3S2/NiO p-n heterojunction for efficient alkaline oxygen evolution

[Display omitted] •NiSO-2p-n heterojunction was rationally designed as an OER catalyst.•The built-in electric field at the interface induces the charge redistribution.•NiSO-2 shows a prominent OER activity in alkaline electrolyte.•The intermediates’ adsorption is optimized by NiSO-2 heterojunction. Nickel-based sulfides/oxides have been widely considered as promising oxygen evolution reaction (OER) electrocatalysts in alkaline water electrolysis. However, how to use the space-charge region of p-n type heterojunction to promote OER activity is a tremendous challenge, and the corresponding attention in water electrolysis is less either, especially for nickel-based sulfides/oxides. Herein, the self-supported Ni3S2/NiO (NiSO-2) p-n type heterojunction nanosheets are designed on nickel foam as an outstanding anodic catalyst for alkaline OER. The internal electric field at the interface of p-n type heterojunction transfers electron from Ni3S2 to NiO and greatly improves electrical conductivity, making Ni3S2 more positively charged and thus more conducive to the chemisorption of intermediates during the OER process. The NiSO-2 electrode shows the small overpotentials of 360 and 400 mV needed to drive large current densities of 200 and 500 mA cm−2, respectively. Furthermore, its robust stability over 100 h at different applied potentials outperforms the most reported OER catalysts. Impressively, density functional theory simulations have been employed to analyse the catalytic mechanisms of NiSO-2 during the OER process. This work provides a reference value to design efficient and durable heterojunction catalysts via manipulating the electronic structure of interface.