Continuous electrolytic methanol synthesis from air-captured CO2 at ordinary temperature and pressure

Abstract

A system for synthesizing methanol (MeOH) from carbon dioxide (CO₂) in the air as a feedstock using electrical energy was developed to open a new avenue for atmospheric carbon capture and utilization. This system integrates three processes: direct air capture (DAC), direct carbonate reduction (DCR), and MeOH synthesis (MeS). A mixture of potassium carbonate and potassium bicarbonate aqueous solutions captures CO₂ from the air as carbonate ions. Carbonate ions in the solution are directly reduced electrolytically to carbon monoxide (CO) using a nanoporous gold electrocatalyst. The produced CO is subsequently reduced electrolytically to MeOH using a cobalt phthalocyanine/carbon nanotube electrocatalyst. The system operated stably for 1.5 h, showing continuous CO₂ capture and MeOH synthesis. This demonstrates the feasibility of the DAC-DCR-MeS integrated system operating under ordinary temperature and pressure conditions throughout all the steps. A notable feature of no need for high temperature or high pressure makes the system compatible with time-varying renewable energies including solar energy, which are essential for reducing net CO₂ emissions.