Enhanced electrochemical oxidation of 5-hydroxymethylfurfural over tailored nickel nanoparticle assembly

Nickel-based materials are promising electrocatalysts for anodic oxidation of 5-hydroxymethylfurfural (HMF) to value-added 2, 5-furandicarboxylic acid (FDCA). However, their catalytic efficiency is impeded by the sluggish phase transformation of Ni(II) hydroxide to the active Ni(III) oxyhydroxide. Herein, we demonstrate for the first time that the phase transformation kinetics and the HMF oxidation activity of nickel nanoparticles can be modulated by creating self-assemblies with different particle aggregation structures: ordered nanoarrays, disordered nanoarrays, and random aggregates. Notably, the nanoparticle assembly featuring an ordered nanoarray structure exhibits the highest activity, achieving 99.8 % HMF conversion and 99.2 % FDCA yield at 1.36 V. In situ Raman spectroscopy and electrochemical analysis reveal that the ordered nanoarray effectively accelerates the transformation kinetics, attributed to the reduced dehydrogenation barrier of Ni(II) hydroxide as confirmed by density functional theory calculations. This work contributes new insights into the structure-performance relationship of Ni-based catalysts, offering valuable guidance for designing high-performing electrocatalysts.