Simple synthesis of a vacancy-rich NiO 2D/3D dendritic self-supported electrode for efficient overall water splitting

Hydrogen production by water electrolysis is a common strategy for the development of renewable energy. However, meeting the industrial requirement for high efficiency and low cost is difficult to achieve with the existing methods. Herein, a novel and simple synthesis route for a dendritic self-supported electrode consisting of oxygen vacancy-rich NiO embedded within ultrathin 2D/3D nanostructures (NiO-Vo@2D/3D NS@DSE) for overall water splitting is developed for the first time. Based on the simple compound synthesis by jet electrodeposition and in situ acid etching, 2D nanosheets adhering uniformly to 3D nanospheres are successfully obtained on the dendritic self-supported skeleton surface. The experiments and density functional calculations illustrate that this electrode integrates the advantages including numerous active sites, intrinsic catalytic activity, good electrical conductivity, and outstanding reaction kinetic performance. Moreover, NiO-Vo@2D/3D NS@DSE shows excellent oxygen evolution reaction and hydrogen evolution reaction activities in 1 M KOH with overpotentials of 230 and 51 mV at 10 mA cm^-2, respectively. Additionally, the electrode, as an alkali-electrolyzer, displays a potential of 1.51 V at 10 mA cm^-2 with favorable stability that is superior to that of IrO₂@nickel foam (NF)//Pt/C@NF (1.62 V). Surprisingly, the cost of NiO-Vo@2D/3D NS@DSE is ≈1/120 of the price of noble electrocatalysts with the same mass. This research opens up a new pathway for the design of bifunctional electrocatalysts.