Decoupled Biomass Electrooxidation Over E-Waste-Derived Au Enables Low-Voltage H₂ and Scalable FDCA Production

The oxygen evolution reaction (OER) constitutes a major energetic bottleneck in electrochemical hydrogen production. Replacing OER with low-potential organic oxidation provides an effective route to reduce cell voltage while enabling value-added chemical synthesis. Here, a nanostructured Au electrocatalyst is developed from recycled electronic waste via a corrosion-template-assisted electrodeposition strategy. Co(OH)₂ nanoarrays grown on nickel foam act as a sacrificial template to regulate galvanic displacement between chloride-coordinated Au(III) species and metallic Ni, inducing polycrystalline Au nucleation with tailored surface structures. Subsequent electrodeposition precisely controls Au size and dispersion, resulting in a substantially enlarged electrochemically active surface area. In alkaline media, the Au electrode selectively drives aldehyde oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furoic acid at potentials well below those required for OER, while enabling concurrent anodic hydrogen evolution and stable low-voltage bipolar hydrogen production. In a flow-electrolysis configuration, current densities of ∼0.6 A cm^-2 are sustained at a low cell voltage of ∼1.2 V for over 200 h. By decoupling low-potential aldehyde oxidation from high-potential deep oxidation in a tandem electrolyzer, stepwise electrochemical upgrading from HMF to FDCA is achieved with reduced overall energy input. This work establishes a scalable electrochemical platform that integrates low-voltage hydrogen production with high-value biomass conversion.