Electronic structure modulation of nickel–iron layered double hydroxide via vanadium doping for enhanced oxygen evolution reaction performance

Abstract

To address the inherent limitations of poor electrical conductivity and sluggish kinetics in nickel–iron layered double hydroxides (NiFe-LDHs) for the oxygen evolution reaction (OER), this study employs a trace vanadium(V) doping strategy to enhance charge transfer kinetics. We successfully synthesized V-doped NiFe-LDH (NiFe-V_x) electrocatalysts, particularly the optimized NiFe-V_1.0/GCE, via a facile hydrothermal method. Comprehensive characterization (SEM, TEM, XRD, EDS, XPS) confirmed that V (1.0 mol.%) is uniformly dispersed within the NiFe-LDH structure primarily as VO₂ (V⁴⁺) and V₂O₅ (V⁵⁺), forming intimate heterointerfaces with the host matrix without altering the characteristic layered nanosheet morphology. This V doping induces significant electronic structure modulation, evidenced by increased Ni³⁺ content and charge transfer between V and Ni/Fe, which downshifts the Ni/Fe d-band center. Electrochemical evaluations in 1 M KOH demonstrated exceptional OER performance for NiFe-V_1.0/GCE: a low overpotential of 254 mV at 10 mA cm⁻², a small Tafel slope of 41.21 mV dec⁻¹, and remarkable stability over 240 hours chronoamperometry and 1000 CV cycles. Mechanistic studies revealed that V doping synergistically enhances performance by: (i) reducing interfacial charge transfer resistance (Rct decreased by 40.8% to 177 Ω cm⁻² via EIS) and inducing a positive shift in flat-band potential, facilitating charge separation; (ii) increasing the electrochemical active surface area by 33% (C_dl = 26.1 mF cm⁻²); and (iii) lowering bulk resistance (R₂ reduced by 39.5%) due to the metallic conductivity of VO₂. This work provides a viable strategy for designing high-performance, non-precious OER electrocatalysts through targeted heteroatom doping.