Electrochemical Hydrogenation of Quinoline Enabled by Cu⁰‐Cu⁺ Dual Sites Coupled with Efficient Biomass Valorization in Aqueous Solution

Abstract

The hydrogenation of nitrogen‐containing heterocyclic precursors in aqueous medium is challenging, especially at ambient temperature and pressure. Electrochemical hydrogenation (ECH) of quinoline to 1,2,3,4‐tetrahydroquinoline (THQ) at mild conditions using water as the hydrogen source is demonstrated with splendid activity on a Cu‐based nonprecicous catalyst. The yield of THQ is up to ≈100% with ≈100% selectivity at −1.275 V vs Hg/HgO. The real active sites and key intermediates are deciphered, where the Lewis acid‐base sites on the heterointerface of Cu/Cu2O are beneficial to the quinoline adsorption in a dual‐site coordination configuration and water dissociation to afford H*. The presence of Cu0 plays a vital role in inhibiting the binding of H*, which ensures good Faradaic efficiency. In addition, a novel co‐production system by coupling benzyl alcohol oxidation at the anode is established, achieving dual benefits in both energy utilization efficiency and economic benefits.