Controlled fabrication of nickel hydroxide electrode with cation vacancies for electrocatalytic oxidation of methanol

The methanol oxidation reaction (MOR) is a key anodic process in direct methanol fuel cells (DMFCs), yet its practical application is hindered by the sluggish kinetics and high cost of noble metal catalysts. Herein, we report a facile alkaline etching strategy to fabricate nickel hydroxide electrodes with tunable cation vacancies (V-Ni(OH)₂/NF) for efficient electrocatalytic methanol oxidation. Starting from NiAl-layered double hydroxide (LDH) nanosheets grown hydrothermally on nickel foam, selective dissolution of Al³⁺ species in concentrated NaOH solution generates well-defined cation vacancies. The vacancy concentration is readily controlled by adjusting the Ni/Al molar ratio in the precursor. Among the obtained catalysts, V_0.1250-Ni(OH)₂/NF exhibits the highest MOR activity, achieving a peak current density of 0.112 A cm^-2 at 1.72 V (vs. RHE) in 1.0 M KOH + 0.4 M CH₃OH, along with good stability. This work demonstrates a vacancy-engineering strategy for designing high-performance, low-cost nickel-based electrocatalysts, offering a promising pathway for sustainable energy conversion technologies.