Remodelling the chlor-alkali electrolysis process to co-generate useful reduction products from CO2

Abstract

Converting CO₂ into usable chemicals and fuels electrochemically is a promising method to close the carbon cycle and store intermittent renewable energy. However, on combining it with a typical anode, the oxygen evolution reaction (OER), results in both high energy consumption and produces only oxygen of little commercial value. Conversely, the chlor-alkali process is an established and profitable electrochemical process that produces Cl₂ and alkali (KOH). Herein, we demonstrate the feasibility of integrating the chlorine evolution reaction (CER) together with the CO₂ reduction reaction (CO₂RR) to co-generate C₄ (2,3-furandiol) and C₃ (methylglyoxal) products. At a cell current of 1 mA, the system produces Cl₂ with a faradaic efficiency (FE) of ∼80% and CO₂RR products at 100% faradaic efficiency without losses from crossover or degradation of the cathode. High faradaic efficiency is achieved for CO₂RR products at higher current densities using a nickel phosphide Ni₂P catalyst synthesized by a low temperature soft-template method. A technoeconomic assessment is presented that quantifies the economic advantage of combining the co-production of methylglyoxal and Cl₂ by integrating these two electrochemical processes.