9:30 AM - 9:45 AM
[MIS26-03] Geo-electrochemical CO production: Implications for the autotrophic origin of life
Hydrothermal activities on the primitive Earth were considered to be much greater than the present level, and hydrothermally produced geo-electrochemical potential may have facilitated CO2 reduction and the formation of organic compounds that preceded the origin of life. To test the possibility, we examined electrochemical CO2 reduction on low-crystalline sulfides of various metals (Ag, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, W, or Zn) in the simulated ancient seawater. Results showed that CdS and Ag2S have excellent catalytic efficiency for the CO2 reduction to CO, together with the H2 evolution. At potentials below -1.0 V (versus the standard hydrogen electrode), the CO production on CdS and Ag2S accounted for around 40 and 30 % of the total electric current, respectively. The threshold potential could be readily generated in the H2-rich, high-temperature and alkaline hydrothermal vents that were probably widespread over the early ocean floor. The electrochemical production of CO, a crucial energy and carbon sources for abiotic and biotic organic synthesis, could have been a key initial step of the prebiotic CO2 fixation in the early ocean hydrothermal systems, and provided the materials for the origin and early evolution of life.