Capture and electrochemical conversion of CO2 to ultrathin graphite sheets in CaCl2-based melts

Molten CaCl2 is reported to be a potential dopant for reactivation of CaO and enhancement of the cyclic capture ability of CaO. The present work showed that O2- in molten CaCl2-CaO has a strong affinity for CO2 at 850 degrees C, with resulting formation of carbonates. Using a RuO2 center dot TiO2 inert anode, the formed carbonates were successfully electrochemically split into value-added ultrathin graphite sheets, which look like a kind of graphene, accompanied by evolution of carbon monoxide at the cathode and environmentally friendly by-product oxygen at the anode. The reduction mechanism of CO32- was investigated by cyclic voltammetry and square wave voltammetry. Results demonstrated that there are two steps in electrochemical reduction of CO32-, and the transferred electron numbers calculated for each step are 1.76 and 1.99, respectively. The kind of graphene generated at the cathode may have applications in fields such as energy storage and electronic devices. The molten CaCl2-CaO has potential applications and prospects in large-scale capture of CO2, and electrochemical conversion of CO2 into high value added carbon material such as ultrathin graphite sheets with renewable energy sources.