Tensile strain engineering on Cu nano-dots for high efficiency HMFOR at low potential

Abstract

The electrochemical conversion of biomass is a promising route to sustainable fuels and chemical feedstocks but is often limited by sluggish catalyst kinetics at low overpotentials. Here, we demonstrate that tensile strain engineering of Cu can substantially enhance its electrocatalytic activity toward the oxidation of biomass-derived 5-hydroxymethylfurfural (HMF). Transmission electron microscopy (TEM) and pair distribution function (PDF) analyses confirmed that continuous tensile strain (0-6%) was introduced into Cu nanoparticles through electroreduction of copper-iodide precursors. The optimized strained Cu catalyst (ID-Cu, 6% strain) achieved a high current density of ~100 mA cm⁻² at 0.3 V vs. RHE, with nearly 100% selectivity toward 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and a Faradaic efficiency of 99%. In situ Raman and FTIR measurements revealed that the adsorption of the key *OCHO intermediate strengthened progressively with increasing strain. Density functional theory (DFT) calculations further showed that tensile strain modulates the Cu d-band center, enhancing the binding energy of *OCHO by 0.9 eV. This work establishes a new paradigm for designing efficient electrocatalysts via lattice strain engineering.