Electrochemical CO2 reduction over Cu could provide value-added multicarbon hydrocarbons and alcohols. Despite recent breakthroughs, it remains a significant challenge to design a catalytic system with high product selectivity. Here we demonstrate that a high selectivity of ethylene (55%) and C2+ products (77%) could be achieved by a highly modular tricomponent copolymer modified Cu electrode, rivaling the best performance using other modified polycrystalline Cu foil catalysts. Such a copolymer can be conveniently prepared by a ring-opening metathesis polymerization, thereby offering a new degree of freedom for tuning the selectivity. Control experiments indicate all three components are essential for the selectivity enhancement. A surface characterization showed that the incorporation of a phenylpyridinium component increased the film robustness against delamination. It was also shown that its superior performance is not due to a morphology change of the Cu underneath. Molecular dynamics (MD) simulations indicate that a combination of increased local CO2 concentration, increased porosity for gas diffusion, and the local electric field effect together contribute to the increased ethylene and C2+ product selectivity.

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Capacitive deionization (CDI) is a promising alternative approach for water desalination and treatment. Hierarchical porous carbons, HPCs, have been viewed as a promising porous structure material for electrosorption purposes. However, limitations associated with the synthesis and porosity control of HPCs limit their utilization as model systems in correlating the textural characteristics and the CDI performance. Here we report for the first time a systematic investigation using a wide range of tightly control primary mesopore size, mesopore surface area, mesopore volume, and high mesopore fraction synthesized by the ice templation approach and correlate to their CDI performance. Larger mesopores are preferable for faster ion removal as they can provide easier pathways for the ions to diffuse and establish the electric double layer. However, smaller mesopores are more preferable in order to achieve higher salt capacity. While for meso–macro HPCs the salt capacity scales up with the mesopore surface area, HPCs that contain all levels of porosity (i.e. micro–meso–macro) do not show such correlation. Besides the excellent CDI performance reported, the model systems allow us to delineate of the role of several materials design parameters and correlate with their electrosorption behavior.