Electrochemical CO₂ reduction provides a promising route to the sustainable generation of valuable chemicals and fuels. Tandem catalysts enable sequential CO₂-to-CO and CO-to-multicarbon (C₂₊) product conversions on complementary active sites, to produce high C₂₊ Faradaic efficiency (FE). Unfortunately, previous tandem catalysts exhibit poor management of CO intermediates, which diminishes C₂₊ FE. Here, we design segmented gas-diffusion electrodes (s-GDEs) in which a CO-selective catalyst layer (CL) segment at the inlet prolongs CO residence time in the subsequent C₂₊-selective segment, enhancing conversion. This phenomenon enables increases in both the CO utilization and C₂₊ current density for a Cu/Ag s-GDE compared to pure Cu, by increasing the *CO coverage within the Cu CL. Lastly, we develop a Cu/Fe-N-C s-GDE with 90% C₂₊ FE at C₂₊ partial current density (j_C2+) exceeding 1 A cm⁻². These results prove the importance of transport and establish design principles to improve C₂₊ FE and j_C2+ in tandem CO₂ reduction.

电化学 CO ₂还原为可持续生产有价值的化学品和燃料提供了一条有希望的途径。串联催化剂能够在互补的活性位点上实现连续的 CO ₂到 CO 和 CO 到多碳 (C ₂₊ ) 产物转化，从而产生高 C ₂₊法拉第效率 (FE)。不幸的是，以前的串联催化剂表现出对 CO 中间体的不良管理，这会降低 C ₂₊ FE。在这里，我们设计了分段式气体扩散电极 (s-GDE)，其中入口处的 CO 选择性催化剂层 (CL) 段延长了后续 C ₂₊选择性段中的 CO 停留时间，从而提高了转化率。这种现象能够增加 CO 利用率和 C通过增加 Cu CL 内的 *CO 覆盖率，Cu/Ag s-GDE 的电流密度比纯 Cu 高 2+ _。最后，我们开发了一种Cu/Fe-NC s-GDE，在C ₂₊部分电流密度( j _C2+ ) 超过1 A cm ^{-2时具有90% C} ₂₊ FE 。这些结果证明了运输的重要性，并建立了设计原则以改进 C ₂₊ FE 和j _C2+串联 CO ₂减少。