Nitrogen-phosphorus co-doped carbon layer-confined cobalt phosphide-anchored nickel molybdate heterojunctions for efficient electrocatalytic overall water splitting

Aiming at the problems of low catalytic activity and poor stability of nickel molybdate-based catalysts. Herein, we successfully prepared nitrogen and phosphorus co-doped carbon (NPC) layer-confined cobalt phosphide (CoP)-anchored nano-cuboid nickel molybdate (NNM) catalysts (NNM-CoP@NPC/NF) on nickel foam (NF) by hydrothermal and phosphating methods. The strong interaction between CoP and NNM is verified by experimental characterization and theoretical calculation, which improves the electronic structure of NNM and reduces the orbital energy of the central anti-bond, thus optimizing the adsorption and desorption of reaction intermediates/products. NiOOH and MoO42- formed by reforming the catalyst under the action of NPC-confined layer maintain catalytic activity and stability in cooperation with CoP and NPC, respectively. Accordingly, in the assembled two-electrode system NNM-CoP@NPC/NF, the cell voltage of only 1.51 V is needed to drive a current density of 10 mA cm- 2. More importantly, the current density remained at 100 mA cm- 2 for 100 h under the voltage of 1.66 V with almost no attenuation. This strategy of constructing interface regulation and confinement provides a new insight for improving the activity and stability of water splitting in alkaline media.