Mesoporous Ni₃S₂@Ni-incorporated and N-doped carbon nanohorn-carbon nanosheets: heterostructure construction and electron modulation for an efficient electrocatalyst for the oxygen evolution reaction

The oxygen evolution reaction (OER) is a key electrochemical reaction in water splitting, but its slow kinetics necessitate the engagement of electrocatalysts to reduce the overpotential and improve reaction efficiency. In this work, a nanocomposite of mesoporous Ni₃S₂@Ni-incorporated and N-doped carbon nanohorns pinned on carbon nanosheets (Ni₃S₂@Ni-CNH-CNS) was prepared by the nickel-catalyzed graphitization of melamine/Span 80 and subsequent partial vulcanization. The nanocomposite electrocatalyst with rich mesopores, abundant exposed active sites and a modulated electronic structure facilitated interfacial electron transference and bulk electron-ion transport for the OER. In 1.0 M KOH, a low overpotential of 210 mV is required for Ni₃S₂@Ni-CNH-CNS to achieve a geometric current density of 10 mA cm^-2, which is lower than the 338 mV for RuO₂ supported on a commercial carbon nanotube. More importantly, Ni₃S₂@Ni-CNH-CNS shows robust durability for OER catalysis at 10 mA cm^-2 within 24 h and maintains a 96% current density in the OER. DFT calculations disclose that the electronic interaction between Ni₃S₂ and Ni-N-C can synergistically regulate the binding energy for the *O intermediate, lower the activation barrier, and consequently enhance the OER catalytic activity.