Highly Efficient Bifunctional Catalyst of NiCo2O4@NiO@Ni Core/Shell Nanocone Array for Stable Overall Water Splitting.

Electrochemical splitting of water is an efficient way to produce clean energy for energy storage and conversion devices. Herein, 3D hierarchical NiCo₂O₄@NiO@Ni core/shell nanocone arrays (NAs) are reported on Ni foam for stable overall water splitting with high efficiency. The architecture and composition of the 3D catalysts are particularly tuned. The outstanding structural and component features of the as-prepared 3D catalysts are characterized by the vertically grown NiCo₂O₄ nanocone/NiO nanosheet core/shell structure and Ni decorated 3D-conductive networks, which largely prompt the catalytic performance. The hybrid catalyst with core/shell nanocone array structures exhibits superior bifuncational activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with an overpotential of 240 and 120 mV at a current density of 10 mA cm⁻², respectively. The Tafel slope of the optimal 3D electrode is about 43 and 58 mV dec⁻¹ in an alkaline electrolyte for OER and HER, respectively. An alkaline electrolyzer constructed by two symmetric NiCo₂O₄@NiO@Ni electrodes delivers splendid activity toward overall water splitting with a current of 10 mA cm⁻² at only ≈1.60 V and almost no deactivation after 10 h. This work provides a promising strategy to design ternary core/shell electrodes as high performance Janus catalysts for overall water splitting. [ABSTRACT FROM AUTHOR]