Electronic structure modulation of nickel-iron layered double hydroxide via vanadium doping for enhanced oxygen...

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 (R ₂ 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.