Designs of Tandem Catalysts and Cascade Catalytic Systems for CO₂ Upgrading

Upgrading CO₂ into multi-carbon (C2+) compounds through the CO₂ reduction reaction (CO₂ RR) offers a practical approach to mitigate atmospheric CO₂ while simultaneously producing high value chemicals. The reaction pathways for C2+ production involve multi-step proton-coupled electron transfer (PCET) and C-C coupling processes. By increasing the surface coverage of adsorbed protons (*H_ad ) and *CO intermediates, the reaction kinetics of PCET and C-C coupling can be accelerated, thereby promoting C2+ production. However, *H_ad and *CO are competitively adsorbed intermediates on monocomponent catalysts, making it difficult to break the linear scaling relationship between the adsorption energies of the *H_ad /*CO intermediate. Recently, tandem catalysts consisting of multicomponents have been developed to improve the surface coverage of *H_ad or *CO by enhancing water dissociation or CO₂ -to-CO production on auxiliary sites. In this context, we provide a comprehensive overview of the design principles of tandem catalysts based on reaction pathways for C2+ products. Moreover, the development of cascade CO₂ RR catalytic systems that integrate CO₂ RR with downstream catalysis has expanded the range of potential CO₂ upgrading products. Therefore, we also discuss recent advancements in cascade CO₂ RR catalytic systems, highlighting the challenges and perspectives in these systems.