Tandem architectures for electrochemical CO2 reduction: from coupled atomic sites to tandem electrolysers.

This Review provides a perspective on tandem catalysis schemes applied to the electrochemical reduction of carbon dioxide (CO2). We define and classify microscopic and macroscopic site and cell tandem concepts pursued so far and provide a critical assessment and performance comparison against non-tandem systems. Our analysis demonstrates that tandem approaches generally seem to improve the selectivity for oxygenates compared with CO2-fed copper-based or non-tandem systems. However, tandem approaches are typically inferior in terms of ethylene production compared with non-tandem approaches. The tandem electrolyser concept seems to be the most promising tandem concept owing to the reduced materials complexity and possibility of individual tuning of microenvironments for the CO-producing and CO-CO-coupling catalytic phases. We conclude our Review by addressing key remaining challenges and promising future research directions in the field of tandem CO2 electrocatalysis.