One-step chemical vapor deposition fabrication of Ni@NiO@graphite nanoparticles for the oxygen evolution reaction of water splitting

Abstract

NiO combined with conductive materials is a practicable way to improve its catalytic property for the oxygen evolution reaction (OER) by enhancing its electrical conductivity. Herein, Ni@NiO@graphite nanoparticles less than 20 nm in average diameter were synthesized by a one-step chemical vapor deposition process. Due to the deliberately controlled lack of oxygen, Ni particles and carbon clusters decomposed from NiCp₂ precursors were oxidized incompletely and formed Ni@NiO core–shell nanoparticles coated by a graphite layer. The thickness of the graphite layer and the content of Ni were controlled by varying deposition temperature. The electrochemical activity towards the oxygen evolution reaction was assessed within alkaline media. Compared with commercial NiO powder, the Ni@NiO@graphite nanoparticles with the unique core–shell microstructure exhibit excellent OER performance, i.e., an overpotential of 330 mV (vs. RHE) at 10 mA cm⁻² and a Tafel slope of 49 mV dec⁻¹, due to the improved electrical conductivity and more active sites. This work provides a facile and rapid strategy to produce nanoparticles with unique microstructures as highly active electrocatalysts for the OER.