Efforts have focused on designing copper-based catalysts to enhance selectivity for multicarbon (C₂₊) products in the electrochemical reduction of carbon dioxide (CO₂). This selectivity is influenced not only by the catalysts but also by the microenvironment surrounding the catalyst layer (CL), including the partial pressures of CO₂ and carbon monoxide (CO), water content, and local pH conditions.

Our study introduces an innovative approach to catalyst layer design to optimize these microenvironmental factors, enhancing C₂₊ product selectivity. The CO₂ reduction reaction (CO₂RR) mechanism indicates that CO is a critical intermediate for C-C coupling, the rate-determining step in generating C₂₊ products. This insight allows the development of cascade reactions that use the CO intermediate to improve C₂₊ yield. We introduce segmented tandem catalyst layers (CLs), a novel configuration consisting of an upstream CO-generation segment (using Ag or Zn) and a downstream Cu segment. This design manages the temporal and spatial concentration of CO in situ, enhancing its utilization and facilitating conversion from CO₂ to CO to C₂₊ products. Unlike conventional CLs with uniform catalyst loading, our approach includes a gradient catalyst loading architecture. This increases CO residence time within the CL, promoting efficient conversion to C₂₊ products. Our design involves a periodic segmented and gradient structure tailored for large electrodes, suitable for industrial-scale cell stacks. Additionally, we have modified the CL composition to enhance hydrophobicity, crucial for CO transport due to its lower solubility in water compared to CO₂. Improved hydrophobicity creates efficient transport pathways for CO, facilitating its conversion.

Combining advanced structural design with optimized composition, we demonstrate that segmented tandem CLs with periodic Ag/Cu segments and Cu loading gradients can achieve over 90% Faradaic efficiency for C₂₊ formation, including about 70% FE for ethylene (C₂H₄) at a partial current density exceeding 1 A cm^-2. Notably, this performance is achieved using commercially available Cu nanoparticles, avoiding the need for complex catalyst synthesis processes.

Huiyue Liu

Appearances