Metal-free electrochemical hydrogenation of activated alkenes by N-doped carbons

Electrochemically-driven organic reactions offer a greener alternative to traditional catalytic methods, which often require harsh conditions. A good example is electrochemical hydrogenation that can be performed under ambient conditions using water as a proton source. To date, commercial (noble) metal electrodes have been used, with less attention given to the development of effective and sustainable electrode materials for these applications. Nitrogendoped carbons (NDCs) have been extensively used in electrocatalysis and energy storage; however, their potential in organic electrosynthesis remains unexplored. In this study, we synthesized a nanoporous NDC derived from 7,7,8,8-tetracyanoquinodimethane via the saltmelt method and applied it to the electrochemical hydrogenation of maleic acid to succinic acid. The NDC exhibited exceptional electrochemical performance, showing an onset potential 0.2 V lower than that of previously reported metal electrodes, along with nearly 100% faradaic efficiency. The SA yield rates were comparable or superior to those achieved by other catalytic methods, while operating under milder conditions and without the use of noble metal catalyst. Moreover, by tuning the potential and electrolyte acidity, the reaction could be driven toward electron-less isomerization to fumaric acid, induced by electrochemical potential.