Regulating electronic structure of two‐dimensional porous Ni/Ni3N nanosheets architecture by Co atomic incorporation boosts alkaline water splitting

Abstract

Abstract Interfacial engineering is a powerful method to improve the bifunctional electrocatalytic performance of pure phase catalysts. While it is expected to further optimize the electronic configuration of heterojunctions to boost the reaction kinetics in hydrogen/oxygen evolution reaction (HER/OER), but remains a challenge. Herein, a novel in situ hybrid heterojunction strategy is developed to construct 2D porous Co‐doped Ni/Ni3N heterostructure nanosheets (Co–Ni/Ni3N) by pyrolysis of partially cobalt substituted nickel‐zeolitic imidazolate framework (CoNi‐ZIF) nanosheets under NH3 atmosphere. A combined experimental and theoretical studies manifest that the hybrid heterostructures can display regulative electronic states and downshift d‐band center from the Fermi level, as well as optimize the adsorption energy of reaction intermediates, thus reducing the thermodynamic energy barriers and accelerating the catalytic kinetics. Consequently, benefitting from the optimized electronic configuration, hierarchical hollow nanosheets architecture, and abundant doped heterojunctions, the hybrid Co–Ni/Ni3N heterostructure catalyst exhibits efficient catalytic activity for both HER (60 mV) and OER (322 mV) at 10 mA cm−2 in alkaline media, which is 105 and 47 mV lower than that of pure Ni3N, respectively. The electrochemically active surface area of Co–Ni/Ni3N is two times higher than that of Ni3N. Furthermore, the coupled practical water electrolyzer requires a low voltage of 1.575 V to reach 10 mA cm−2, and it can be driven by a 1.5 V battery. This work highlights the interface engineering guidance for the rational establishment of hybrid interfaces by electronic modulation of interfacial effect for alkaline water splitting.

Keywords

• 2D porous nanosheet
• hybrid heterojunction
• interfacial engineering
• nickel nitride
• overall water splitting