Sulfur-modified copper nanowire substrate with Prussian blue analogue reconstruction: a dynamic electrocatalyst for biomass-derived HMF oxidation†

Abstract

This study reports a non-precious electrocatalyst, CuS-NWs@PBAs (copper sulfide nanowires functionalized with Prussian blue analogues), for the efficient oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) under mild conditions. The catalyst was synthesized via a three-step electrodeposition process on a sulfurized copper foam substrate, where sulfurization enhanced substrate conductivity, reducing charge-transfer resistance by 90% compared to unsulfurized counterparts. Operando Raman and XPS spectroscopy revealed that the dynamic reconstruction of PBAs into NiOOH/Ni(OH)₂ during alkaline activation created porous architectures with optimized Ni coordination environments, significantly lowering the energy barrier for the rate-determining FFCA → FDCA step. The optimized catalyst achieved 99.8% HMF conversion and 95.2% FDCA yield at room temperature with a low overpotential (0.35 V vs. HgO) and Tafel slope, outperforming most reported noble-metal systems. Systematic electrochemical analysis demonstrated high faradaic efficiency (>93%) and selectivity for the HMF → FDCA pathway, while control experiments validated the critical role of sulfurization and PBA reconstruction. Furthermore, the catalyst exhibited dual functionality in glycerol and urea oxidation, suggesting broader applicability. This work provides mechanistic insights into the dynamic evolution of transition metal catalysts and offers a practical strategy for designing cost-effective electrocatalysts for sustainable biomass valorization.