Temperature-Tuned Electrocatalytic Valorization of Levulinic Acid to γ-Valerolactone or 4-Hydroxyvaleric Acid over...

Temperature-modulated electrocatalytic hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) or 4-hydroxyvaleric acid (HVA) was investigated over CuNi and CuNiRu catalysts electrodeposited onto vertically aligned graphene nanowalls. Systematic potential (-1.6 to -2.0 V vs. Ag|AgCl) and temperature (5°C-50°C) studies revealed a clear product switch: at 5°C all catalysts showed > 95% selectivity to HVA, whereas at 50°C GVL dominated. Among the compositional configurations, trimetallic CuNiRu (50 mC cm^-2) achieved the highest performance, affording 96.6% LA conversion, 92.4% GVL yield, and 98.5% selectivity at 50°C with minimal Ru loading. The synergy between Ru sites (promoting hydrogen activation and lactonization) and the high-roughness nanowall scaffold suppressed H₂ evolution, minimized metal leaching (<1%), and delivered stable operation under ambient pressure. The system maintained performance over multiple cycles and preserved selectivity even under concentrated LA solutions, confirming architectural robustness. Faradaic efficiencies up to 89%, low energy consumption (~0.12  kWh  mol^-1), and energy storage efficiencies > 70% underscore the viability of this system for direct electricity-to-fuel conversion. These temperature-potential insights establish a tuneable platform where low-temperature operation yields HVA, whereas moderate temperatures (50°C) enable near-quantitative GVL production.