From maleic to succinic acid: Electrochemical reduction as a game-changer for green electro-refinery schemes

The selective conversion of maleic acid (MA) to succinic acid (SA) is traditionally achieved by high-pressure catalytic hydrogenation. This route requires external hydrogen and significant energy input. Electrochemical reduction offers a viable alternative. It enables MA-to-SA conversion under ambient conditions and allows mechanistic control through electrode selection and current density. Cyclic voltammetry shows direct electron-transfer reduction of MA and SA on Cu electrodes. Ni displays negligible activity toward MA. Polarization studies indicate that Cu favors MA reduction, whereas Ni accelerates SA reduction. These trends highlight the influence of molecular structure on electrode–substrate interactions. Bulk electrolysis yields selective MA-to-SA conversion with Faradaic efficiencies up to 96 %. High electron-transfer rates are essential to suppress competing pathways. Stability tests reveal that SA undergoes over-reduction at high current densities, particularly on Ni. This finding emphasizes the need to balance productivity with product preservation. Complementary hydrogenation experiments broaden the valorization scope. Residence time and hydrogen availability govern selectivity, ranging from partially hydrogenated intermediates to deeply hydrogenated volatiles. Overall, the results support a dual-path electro-refinery strategy for sustainable SA production. The approach integrates mild electroreduction with controlled deep hydrogenation. It offers a scalable and low-carbon route for incorporating dicarboxylic acids into next-generation chemical and fuel manufacturing. • Copper enables efficient electrochemical reduction of maleic to succinic acid. • Nickel shows negligible activity for MA but favors SA kinetics under polarization. • Bulk electrolysis achieves high Faradaic efficiency under mild operating conditions. • Current density strongly governs selectivity and prevents undesired over-reduction. • Hydrogenation expands valorization, tuning products via residence time and H 2 supply.