Tuning the microenvironment of immobilized molecular catalysts for selective electrochemical CO₂ reduction

The electrochemical CO₂ reduction reaction (CO₂RR), as a novel technology, holds great promise for carbon neutrality. Immobilized molecular catalysts are considered efficient CO₂RR catalysts due to their high selectivity and fast electron transfer rates. However, at high current densities, changes in the microenvironment of molecular catalysts result in a decrease in the local CO₂ concentration, leading to suboptimal catalytic performance. This work describes an effective strategy to control the local CO₂ concentration by manipulating the hydrophobicity. The obtained catalyst exhibits high CO selectivity with a Faradaic efficiency (FE) of 96% in a membrane electrode assembly. Moreover, a consistent FE exceeding 85% could be achieved with a total current of 0.8 A. Diffusion impedance testing and interface characterization confirm that the enhanced hydrophobicity of the catalyst layer leads to an increase in the thickness of the Nernst diffusion layer and an expansion of the three-phase interface, thereby accelerating CO₂ adsorption to enhance the performance.