Thioester Synthesis by Geoelectrochemical CO2 Fixation on Ni Sulfides

Thioester synthesis via CO2 fixation by CO dehydrogenase/acetyl-CoA synthase is among the most ancient autotrophic metabolism often suggested to have a prebiotic root. Here we demonstrate that, under an electrochemical condition realizable in early ocean hydrothermal systems, nickel sulfide (NiS) gradually reduces to Ni0, thereby drastically enhancing its capability of driving nonenzymatic CO2 fixation. It catalyzes CO2 electroreduction to CO, concentrates CO on the surface Ni0 sites, and promotes CO condensation to a thioester in the presence of methanethiol. Even greater CO-to-thioester reaction efficiency is realized with NiS coprecipitating with FeS or CoS. Considering the central role of Ni in the enzymatic process mentioned above, our demonstrated thioester synthesis by the partially electroreduced NiS could have a direct implication to the autotrophic origin of life.