Coupling Electrochemical Sulfion Oxidation with CO₂ Reduction over Highly Dispersed p-Bi Nanosheets and CO₂-Assisted Sulfur Extraction

We report herein an electrocatalytic CO₂ reduction-coupled sulfion oxidation system for the co-productions of valuable formate and sulfur at much enhanced atom utilization. Specifically, an organic ligand-assisted two-step reconstruction approach has been developed to fabricate the highly dispersed p-Bi nanosheets (p-Bi NSs) for cathodic CO₂ reduction reaction (CO₂RR), and meanwhile porous Co−S nanosheets (Co−S NSs) was applied for anodic sulfion oxidation reaction (SOR). Significantly high Faradaic Efficiencies of about 90 % for formate production by CO₂RR in a wide potential range from −0.6 V to −1.1 V, and excellent SOR performances including an ultra-low onset potential of about 0.2 V and recycle capacity of S²⁻ in the 0.1 M and 0.5 M S²⁻ solutions, have been simultaneously achieved. In the meantime, both the structure transformation of the catalysts and the reaction pathways are explored and discussed in detail. A two-electrode CO₂RR||SOR electrolyzer equipped with above electrocatalysts has been established, which features as low as about 1.5 V to run the electrolyzer at 100 mA cm⁻², manifesting extremely lowered electricity consumption in comparison to conventional CO₂RR system. Moreover, a sulfur separation approach has been proposed by using CO₂, which is efficient, environmentally friendly and cost effective with value-added NaHCO₃ be obtained as the byproduct.