Multiscale effects in tandem CO₂ electrolysis to C₂₊ products

CO₂ electrolysis is a sustainable technology capable of accelerating global decarbonisation through the production of high-value alternatives to fossil-derived products. CO₂ conversion can generate critical multicarbon (C₂₊) products such as drop-in chemicals ethylene and ethanol, however achieving high selectivity from single-component catalysts is often limited by the competitive formation of C₁ products. Tandem catalysis can overcome C₂₊ selectivity limitations through the incorporation of a component that generates a high concentration of CO, the primary reactant involved in the C-C coupling step to form C₂₊ products. A wide range of approaches to promote tandem CO₂ electrolysis have been presented in recent literature that span atomic-scale manipulation to device-scale engineering. Therefore, an understanding of multiscale effects that contribute to selectivity alterations are required to develop effective tandem systems. In this review, we use relevant examples to highlight the complex and interlinked contributions to selectivity and provide an outlook for future development of tandem CO₂ electrolysis systems.