Electronic structure reconfiguration of nickel–cobalt layered double hydroxide nanoflakes via engineered heteroatom and oxygen-vacancies defect for efficient electrochemical water splitting

Abstract

The development of earth-abundant and high-efficiency bifunctional electrocatalysts is extremely desirable for electrochemical water splitting, but there are some critical challenges that need to be addressed. The coordinated tailoring of electronic structure and Bader charge transference by heteroatom doping and oxygen vacancy defects are one of the strongest tactics to enhance the oxygen and hydrogen evolution reactions (OER and HER) of catalysts. Herein, a novel Mo-decorated nickel–cobalt layered double hydroxides 3D honeycomb nanoflake on Ni foam (labeled as Mo-NiCo LDHs(Vo)) as bifunctional electrode materials with enriched oxygen vacancy defects, excellent geometric stability, and enriched active sites was successfully fabricated through a facile hydrothermal reaction strategy. Density functional theory computations and experimental results confirmed that the electrocatalytic intrinsic activity of Mo-NiCo LDHs(Vo) was optimized not only because of the provision of new active sites by the Mo dopants via the construction of defects and oxygen vacancies but also because of the activation of the local electronic structures of the surrounding Ni and Co sites. Consequently, Mo-NiCo LDHs(Vo) exhibited outstanding electrocatalytic performance with an overpotential of 258 mV for OER and 194 mV for HER at a current density of 10 mA/cm2 in an alkaline medium. In addition, the catalyst exhibited excellent long-term stability after 100 h of use as a bifunctional electrode for overall water splitting. This work provides a facile means to fabricate superior, efficient noble metal-free catalysts with well-designed defects at the atomic-level using electronic structure engineering for energy-related applications.