High-Performance Zero-Gap Glycerol-Fed Electrolyzer for C₃ Chemicals and Hydrogen Production

The electrochemical oxidation of biomass-derived glycerol offers a promising low-voltage alternative to water oxidation in electrolyzers, enabling the co-production of hydrogen and value-added chemicals. However, achieving high conversion rates at current densities above 300 mA cm^-2 remains challenging due to the rapid deactivation of platinum-based catalysts. Here, we present a membrane electrode assembly (MEA) featuring a platinum-decorated nickel foam (Pt/NiF) anode that sustains operation for 24 h at 500 mA cm^-2 with an average cell voltage of just 1.21 V, outperforming all previously reported glycerol-fed electrolyzers operating below 1.5 V. The system exhibits >88% selectivity toward C3 products, achieving 227 mA cm^-2 partial current density for lactic acid and 9% single-pass glycerol conversion. In situ impedance spectroscopy identifies voltage-dependent regimes linked to platinum hydroxide formation, glycerol oxidation, and oxygen evolution. Systematic variation of electrolyte composition and temperature reveals an optimized window (1.2-1.4 V, 55-65°C) for sustained performance. Under these conditions, a single 24 h cycle co-generates ∼175 mmol of H₂ and 45 mmol of C3 products. These results establish new operational and mechanistic benchmarks for efficient, low-voltage electrochemical valorization of biomass-derived polyols at industrially relevant rates.