Functionalizing Lignin-Based Nanofiber Electrodes with Gold Using Electrochemically Assisted Aqueous Reduction

This work demonstrates how the electrochemically assisted aqueous reduction (EAR) method can be employed with lignin to prepare functional surfaces from underutilized resources. First, electrospun lignin nanofiber mats are carbonized at 700, 900, and 1100 °C to prepare electrodes with conductivities between 1.1 and 12 S cm⁻¹. The films are then functionalized with EAR, which allows for gold (5 mg L⁻¹) to be selectively deposited as nanoparticles from acidic chloride solutions containing much larger concentrations of copper (20 g L⁻¹), mimicking hydrometallurgical process conditions. The successful functionalization by gold nanoparticles is confirmed by the electrochemical oxidation of ethanol and reduction of carbon dioxide, thus highlighting the use of secondary raw materials in a high added-value application.