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 (eCO₂R) 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 eCO₂R, 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 CO₂Rs. 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 eCO₂R technologies is provided.