Electrochemical behavior of Cu-mediated electrowinning-coupled CO2 capture

Abstract

The emerging electrochemical CO2 captures are energy-intensive or inefficient (operated at low current density). Here, we proposed a promising electrowinning-coupled CO2 capture (ECC) system using copper (Cu) as electrochemical mediator and ammonia (NH3) as CO2 absorbent to advance the electrically-driven approach. The Cu-mediated ECC process used the electro-active competitor of Cu(NH)42+/Cu to achieve efficient electrochemical CO2 desorption and NH3 regeneration at desirable energy consumption. To elucidate the electrochemical behavior of the CO2 desorption and NH3 regeneration, we performed experimental electrochemical analysis. This inspired us that to ensure a desired electrodissolution-coupled competitive complexation of Cu2+, CO2 with NH3 and electrodeposition-coupled separation of Cu2+ from NH3, efficient redox-active reaction of Cu(NH)42+/Cu should be achieved. We developed micro-kinetics process model, which achieved energy requirements of 47.1–50.2 kJe/mol CO2. This energy performance was competitive with the 100–500 kJe/mol of other advanced electrochemical CO2 capture approaches. The modeling energy consumption was very close to that of the value obtained from bench-scale ECC electrolysis. It is anticipated that the Cu-mediated ECC process would provide an energy-efficient pathway with desirable Faradaically-driven operational efficiency, ultimately advancing electrochemical CO2 capture towards industrial application.