Designs of Tandem Catalysts and Cascade Catalytic Systems for CO Upgrading.

Upgrading CO into multi-carbon (C2+) compounds through the CO reduction reaction (CO RR) offers a practical approach to mitigate atmospheric CO 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 ) and *CO intermediates, the reaction kinetics of PCET and C-C coupling can be accelerated, thereby promoting C2+ production. However, *H 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 /*CO intermediate. Recently, tandem catalysts consisting of multicomponents have been developed to improve the surface coverage of *H or *CO by enhancing water dissociation or CO -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 CO RR catalytic systems that integrate CO RR with downstream catalysis has expanded the range of potential CO upgrading products. Therefore, we also discuss recent advancements in cascade CO RR catalytic systems, highlighting the challenges and perspectives in these systems.