Strong Ni–S Hybridization in a Crystalline NiS Electrocatalyst for Robust Acidic Oxygen Evolution

Developing low-cost, active, and stable electrocatalysts toward acidic oxygen evolution reaction (OER) is highly desirable for proton electrolyte membrane electrolyzers to produce renewable H2 energy. Here, we report a noble metal-free NiS-based electrocatalyst suitable for acidic OER media through a facile one-step pyrolysis approach. The prepared NiS particles display high crystallinity and are coupled on a sulfur-doped carbon nitrogen support. Synchrotron X-ray spectroscopies demonstrate that the strong hybridization of Ni and S not only provides a favorable electronic structure for the adsorption and dissociation of water but also offers high stability against the corrosive acidic media. Consequently, the NiS-based electrocatalyst exhibits high efficiency and stable OER performance with a low overpotential of 337 mV at a current density of 10 mA cm–2 with a Tafel slope of 53.2 mV dec–1.