3D nickel-cobalt diselenide nanonetwork for highly efficient oxygen evolution

Active, stable and low-cost oxygen evolution reaction (OER) catalyst for electrochemical water splitting is key to efficient energy conversion and storage. Here, we report a three-dimensional (3D) nanonetwork as noble-metal-free electrode consisting of nickel cobalt diselenide (NiCoSe₂) nanobrush arrays on Ni foam (NF) through the initial hydrothermal reaction and subsequent thermal selenization process. Introducing ammonium fluoride as surface controller, different NiCoSe₂ hierarchical architecture can be modulated from nanorods, nanobrush to nanosheets. The unique brush-like NiCoSe₂ possesses high surface area for mass transfer, rough surface with rich active sites, 3D nanostructure preventing the accumulation of O₂ bubbles. Compared to NiCoSe₂ nanorods/NF, NiCoSe₂ nanosheets/NF and commercial RuO₂, NiCoSe₂ nanobrush/NF exhibits an enhanced OER performance in alkaline media to reach a low overpotential of 274mV at the current density of 10mA/cm², small Tafel slope and a long-term stability. The developed 3D nanonetwork highlights the nanoscale engineering and offers a promising alternative to noble metal catalysts for electrochemical water oxidation.