Pulse-Mediated Refaceting of Copper. Influence on 5-Hydroxymethylfurfural Electrocatalysis

Abstract

This work evaluates the impact of the reduction potential (ER) on the pulse-mediated formation of high-index facet structures on Cu(111) and copper polycrystalline electrode in sodium chloride (NaCl) electrolyte. Cyclic voltammetry (CV), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM) were combined to correlate grain orientation and surface morphology changes with experimental conditions that drive shape formation. Furthermore, we have performed a comprehensive voltammetric analysis across a broad range of stepped single-crystal electrodes, demonstrating that blank CVs of the Cu | 0.1 M NaCl interface effectively decouple terrace and step contributions on copper. Our study revealed that while chloride tends to induce structures comprising (100) terraces and ( 111) or ( 110) defects under oxidation-reduction potential pulse conditions, the deposition rate, determined by the ER, controls the length of the generated (100) terraces and defect density.The oxidation and reduction of 5-hydroxymethylfurfural (HMF) were investigated as model structure-sensitive reactions to probe how variations in the terrace-to-defect ratio affect catalytic behaviour. Low-coordinated sites promote oxidation of HMF, whereas (100) terraces adjacent to steps decrease the onset potential for HMF reduction. By identifying the active surface facets, this work demonstrates that surface structure engineering is a powerful approach to advance electrocatalysis on copper.