Iodide-mediated electroreduction of carbon dioxide for efficient and selective electrosynthesis of multicarbon products over copper iodide microcrystals.

Electrochemical CO2 reduction (e-CO2RR) to multicarbon (C2+) products serves as a sustainable route for renewable energy storage, chemical synthesis, and mitigating CO2 emission. In this study, we report on the CuI microcrystals modified gas-diffusion electrode (microCuI), prepared with the successive ion layer adsorption and reaction method, with high-performance towards the generation of C2+ products from e-CO2RR. The microCuI electrode exhibited remarkably high current efficiency towards the generation of C2+ products (i.e., ethylene, ethanol, and 1-propanol), but suffered instability due to the formation of inactive copper (II) carbonate hydroxide within 2-h electrolysis. As compared to other halide ions, the inclusion of a suitable amount of I- ions during the electrolysis minimized the corrosion and effectively regulated the oxidation state of surface copper species (OSCu) and transformed microCuI into aggregates of Cu0/Cu2O nanoparticles, with Cu0 embedded in a Cu2O matrix. The suitable OSCu (∼0.7) combined with synergistic catalytic effects from Cu0 and Cu2O enabled high stability and realized high current efficiency (73.6 ± 2.2 %) and high energy efficiency (48.8 ± 1.8 %) for the generation of C2+ products in the prolonged electrolysis at -100 mA cm-2. Finally, the I- ion-mediated e-CO2RR scheme was also demonstrated to effectively boost the current efficiency and energy efficiency of the microCuI electrode towards the generation of C2+ products from the electrocatalytic reduction of low-concentration CO2 in the simulated biogas atmosphere.