Towards highly efficient electrochemical CO2 reduction: Cell designs, membranes and electrocatalysts

An increase in atmospheric CO2 concentration is directly associated with the rising concerns of climate change and energy issues. The development of effective technologies for capture and utilization of atmospheric CO2 is required to mitigate these global challenges. Electrochemical CO2 reduction (eCO(2)R) is one of the most promising approaches for the conversion of excess renewable energy sources into storable fuels and value-added chemicals. This field has recently advanced enormously with impressive research achievements aiming at bringing the technology on the brink of commercial realization. Herein, we present a comprehensive review analyzing the recent progress and opportunities of using different cell designs with the main focus on membrane-based flow cells for eCO(2)R, along with the required system-level strategies for optimal engineering to enhance electrocatalytic selectivity and efficiency. Research advance on the use of different polymer electrolyte membranes for CO2 electrolyzers is updated. Main achievements in new catalyst discoveries are assessed in terms of activity, selectivity, stability together with CO2R reaction kinetics. This was supported by the analysis of the computational studies performed to devise the effective catalyst design routes and to understand the pathways for CO(2)Rs. The interactive effect of the design of reactors and gas diffusion electrodes with catalysts is analyzed for different operating conditions (like pH, temperature and pressure) of CO2 electrolyzers. Finally, an outlook on future research directions in terms of material and process design for a breakthrough in eCO(2)R technologies is provided.