Bimetal−Organic Framework Derived High‐Valence‐State Cu‐Doped Co3O4 Porous Nanosheet Arrays for Efficient Oxygen Evolution and Water Splitting

Abstract Developing low‐cost, high‐efficient, and robust electrocatalysts for oxygen evolution reaction (OER) holds promise for the future hydrogen economy through overall water splitting. Herein, Cu doped Co 3 O 4 porous nanosheet arrays were synthesized on three‐dimensional (3D) nickel foam (Cu−Co 3 O 4 NAs/NF) by a facile pyrolysis process of bimetal−organic frameworks precursors. The systematic experiments evidence that the Cu doping in Co 3 O 4 materials not only results in affluent trivalent cobalt as active sites for OER electrocatalysis, but also modulates the nanosheet morphology to achieve high specific surface area and well‐exposed active sites. Moreover, the 3D electrode configuration simultaneously offers open‐channels for electron transport and gas products release. Benefitting from the exotic geometric and electronic structure, the engineered Cu−Co 3 O 4 NAs/NF electrode exhibits outstanding activity (an overpotential of 230 mV at 10 mA cm −2 ) and long‐term durability toward OER, much better than the benchmark IrO 2 /NF. Together with its remarkable HER activity, our Cu−Co 3 O 4 NAs/NF electrode enables a low voltage of 1.58 V to generate a current density of 10 mA cm −2 for overall water splitting, which is comparable to those of current Co‐based bifunctional electrocatalysts. This work may open up opportunities to explore other advanced electrocatalysts with high valence Co 3+ and 3D porous architectures for scale‐up water electrolysis.