NiCo LDH-derived defect-engineered Se-doped NiCoP mesoporous nanoflowers for enhanced oxygen evolution reaction

Abstract

The rational design and development of doped and defect-engineered electrocatalysts are vital for enhancing the oxygen evolution reaction (OER) during water electrolysis for sustainable energy conversion. In this study, a NiCo LDH precursor was first synthesized via a solvothermal route and anchored on nickel foam (NF), followed by a one-pot phospho-selenization process to simultaneously introduce Se doping and P vacancy into a bimetallic phosphide nanoflower architecture (NCP–Se/NF). The optimized NCP–Se/NF catalyst requires the smallest overpotential of only 260 mV to achieve a current density of 10 mA cm⁻². It exhibits the lowest Tafel slope of 28.17 mV dec⁻¹ compared with bimetal phosphide (NCP/NF) and the parent LDH (NCL/NF). It exhibits long-term durability, maintaining 84.1% of its original activity even after 50 hours of operation under anodic conditions in an alkaline electrolyte. The synergistic effect of Se doping and P vacancy manipulation alters the electronic redistribution around the Ni/Co sites, which subsequently optimizes the d-band centre, providing a more exposed active site, minimizing the diffusion path length, and reducing the kinetic energy barrier for the OER. The P vacancy is evidenced by XPS and EPR analyses. Furthermore, the use of CTAB as a surfactant template in synthesis generates mesopores within the nanoflower structure, significantly increasing the specific surface area and facilitating the electrolyte penetration, which in turn promote rapid oxygen bubble release. This work highlights the use of combined heteroatom doping and vacancy-engineering strategies to provide an effective route for the design of high-performance electrocatalysts for efficient water oxidation.