Fouled electrodes: Density gradient-driven convection augments aqueous electrosynthetic yields

• Partially fouled electrodes enhance aqueous electrosynthetic rates. • Density-gradient convection augments mass transport near insulators. • nLOF 2035 and SU-8 2002 photoresists boost levulinic acid and l -ascorbic acid conversions. • Gravity-aligned (vertical) cells further amplify electrosynthetic yields. Organic electrosynthesis offers sustainable pathways for chemical manufacturing. Electrode surface properties strongly influence electrosynthetic efficiency; hence, electrode contamination by non-conductive materials generally suppresses reaction rates. However, recent studies indicate that lateral surface heterogeneity – conductive regions interspersed with insulating domains – induces density gradients that, under gravity, augment rates by promoting natural convection in otherwise quiescent systems. Here, we show that convection triggered by partial electrode fouling enhances the rate of model electrosynthetic processes. We have quantitatively assessed the extent to which fouling promotes mass transport and increases net electrolytic rates per unit area for the electro-reduction of levulinic acid (LA) to valeric acid (VA) and for the electro-oxidation of l -ascorbic acid (LAA) to dehydroascorbic acid (DHAA). Specific patterns of microscopic insulating features were deposited on glassy carbon, lead, and indium tin oxide electrodes through photolithography. Despite a reduction in electroactive area, fouled electrodes showed higher yields than pristine ones. Large-scale patterns of relatively hydrophilic novolak resin (nLOF 2035) enhanced LA-to-VA conversion by up to 1.8–fold, while the epoxy-based SU-8 2002 photoresist improved LAA oxidation by 1.22–fold. Moreover, when electrodes were aligned vertically relative to gravity, buoyancy-driven convection, hence electrolytic rates, are further amplified. This work establishes a new framework for reactor and electrode design in which controlled surface blocking is harnessed to augment, rather than hinder mass transport, opening new opportunities for organic electrosynthesis.