High-Entropy Layered Double Hydroxides for Efficient Methanol Electrooxidation

Abstract

The electrocatalytic methanol oxidation reaction (MOR) is considered as an effective method to replace oxygen evolution reaction (OER) for efficient hydrogen production. However, the sluggish kinetics and the difficulty of breaking C─H bond of the Ni-based catalysts limit further application. Herein, three high-entropy layered double hydroxides (HELHs), namely ZnNiFeCoV-HELH, ZnNiFeCoCr-HELH, and ZnNiFeCoAl-HELH (denoted as V-HELH, Cr-HELH, and Al-HELH, respectively), are successfully synthesized. Among them, the V-HELH displays the lowest potential of 1.39 V at 100 mA cm⁻² compared to Cr-HELH (1.41 V) and Al-HELH (1.44 V). After five cycles, the formate yield of V-HELH maintains over 95% of the first cycle with excellent stability. Such outstanding performance surpasses that of most state-of-the-art MOR catalysts reported so far. A series of experiments reveal that the V-HELH exhibits the fastest reaction kinetics and the largest number of active Ni³⁺ species. Further investigations and theoretical calculations prove that the V-HELH shows the strongest methanol adsorption with the lowest energy of −3.31 eV. The introduction of vanadium (V) with relatively larger tensile strain optimizes the d─band center of V-HELH (−0.54 eV) and lowers the energy barrier (−1.62 eV) from ^*CH₃O to ^*CH₂O. This work provides new insights for rational design of efficient MOR electrocatalysts.