Co-electrolysis toward value-added chemicals

Current major electrocatalytic reactions, such as hydrogen evolution reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction, focus on single-target chemical production, which suffers from strong competitive reactions at the same electrodes and/or high energy barrier reactions at the counterpart electrodes. The co-electrolysis of more than one kind, typically two kinds, of chemical precursors in one electrolytic system is therefore a highly attractive strategy for both energy input reduction and concurrent production of double value-added chemicals. Exciting progress has been achieved in this area recently, and a timely review on this specific topic will be highly desired. In this review, the reported co-electrolysis systems are classified into four categories: (1) agent sacrificing at one electrode promoting electrochemical precursor conversion at the other; (2) parallel electrochemical precursor conversions, i.e., electrosyntheses, simultaneously at both sides; (3) electrochemical conversions of two precursors at both sides into one/the same product; (4) double/multiple electrochemical conversions at one side. The current challenges and future opportunities of co-electrolysis toward high value-added products are discussed at the end.