A Stable Graphitic, Nanocarbon-Encapsulated, Cobalt-Rich Core–Shell Electrocatalyst as an Oxygen Electrode in a Water Electrolyzer

The oxygen electrode plays a vital role in the successful commercialization of renewable energy technologies, such as fuel cells and water electrolyzers. In this study, the Prussian blue analogue-derived nitrogen-doped nanocarbon (NC) layer-trapped, cobalt-rich, core–shell nanostructured electrocatalysts (core–shell Co@NC) are reported. The electrode exhibits an improved oxygen evolution activity and stability compared to that of the commercial noble electrodes. The core–shell Co@NC-loaded nickel foam exhibits a lower overpotential of 330 mV than that of IrO₂ on nickel foam at 10 mA cm⁻² and has a durability of over 400 h. The commercial Pt/C cathode-assisted, core–shell Co@NC–anode water electrolyzer delivers 10 mA cm⁻² at a cell voltage of 1.59 V, which is 70 mV lower than that of the IrO₂–anode water electrolyzer. Over the long-term chronopotentiometry durability testing, the IrO₂–anode water electrolyzer shows a cell voltage loss of 230 mV (14%) at 95 h, but the loss of the core–shell Co@NC–anode electrolyzer is only 60 mV (4%) even after 350 h cell-operation. The findings indicate that the Prussian blue analogue is a class of inorganic nanoporous materials that can be used to derive metal-rich, core–shell electrocatalysts with enriched active centers.