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.