Stabilizing Cu+ active sites by small molecule modulation on copper electrocatalyst for boosting semi-hydrogenation of alkynes in water

A citric acid (CA) modified EDCu-CA catalyst was constructed for the electrocatalytic semi-hydrogenation of alkynes with 99% olefins selectivity. CA can regulate the electronic structure of copper, stabilize the Cu + active site, and Cu + can inhibit the over-hydrogenation of olefins. • EDCu-CA exhibits more than 97% alkyne conversion and 99% olefin selectivity. • CA modulates and stabilizes the Cu+ active site during the electroreduction. • Wide range of alkyne substrates and industrial feasibility for g-level conversion. Selective electrocatalytic semi-hydrogenation (ECSH) of alkynes in water using Cu catalysts is highly relevant for the production of value-added chemicals. However, achieving high olefin selectivity still poses extreme challenges due to the susceptibility of the copper cathode in a reduction environment. Herein, a small molecule modulation electrodeposition strategy is introduced that regulates the structure of Cu-based materials through modification with citric acid (CA) ligands, aiming for highly active and selective ECSH. The as-prepared EDCu-CA electrode achieves more than 97% alkyne conversion and 99% olefin selectivity. In-situ Raman and Auger electron spectroscopy (AES) data provide evidence that active Cu + sites can stably exist in the EDCu-CA during the catalytic process. Density functional theory (DFT) calculations indicate that the modulation by CA contributes to maintaining Cu in a positive valence state, and Cu + can inhibit the over-hydrogenation of olefins. Moreover, by utilizing a large-area electrode for long-term electrolysis, g-level conversion and a 92% separation yield of olefin can be achieved, demonstrating a viable application prospect. This study offers a promising route for designing Cu-based catalysts for the highly selective electrocatalytic conversion of organic substrates to value-added chemicals in water.