Etching reconstruction of ultrathin layered NiFe-hydroxide: building synergistic VFe(III)/Ni(iii) active structures for an efficient urea oxidation reaction

Abstract

Plagued by excessively thick layered structures and insufficient active sites, nickel–iron layered double hydroxide (NiFe-hydroxide) catalysts exhibit sluggish kinetics for the urea oxidation reaction (UOR), severely limiting their practical applications in urea wastewater treatment and energy-saving hydrogen production. Herein, atomic-scale precision reconstruction of ultrathin layered NiFe-hydroxide materials was employed to build a V_Fe(III)-Ni₂Fe-LDH catalyst with a high density of iron vacancies and synergistic high-valence Ni for an efficient UOR. This targeted etching strategy achieves dual optimization by structurally promoting an ultrathin layered architecture that significantly increases the specific surface area and exposes more active sites, while electronically introducing iron vacancies to restructure the local coordination environment, thereby facilitating electron rearrangement of nickel and promoting the formation of key Ni³⁺ active species. Benefiting from this synergistic enhancement, the V_Fe(III)-Ni₂Fe-LDH catalyst delivers exceptional UOR performance, requiring only 136 mV to achieve a current density of 100 mA cm⁻², and exhibiting a Tafel slope of 16.1 mV dec⁻¹, which are markedly lower than those of the unetched Ni₂Fe-LDH. Density functional theory (DFT) calculations reveal that this enhancement originates from strengthened Ni(d)–O(p) orbital hybridization, which optimizes the electronic structure of active sites and accelerates charge transfer kinetics, thereby demonstrating great potential for UOR-related clean energy applications.