Electrolyte Effect on Electrochemical CO₂ Reduction to Multicarbon Products

The ever-growing environmental concern has yielded the electrocatalytic carbon dioxide reduction (eCO(2)R) center of research attention, as it offers a possible pathway to achieve net-zero carbon emission and realize a post-fossil-fuel society. The production of multicarbon (C2+) species with higher energy density is more desirable but unfortunately presents a greater challenge. Other than the catalyst itself, the electrolyte has also been demonstrated to exhibit nontrivial impacts on eCO(2)R, a systematic understanding on the effect of which therefore remains vital. In this Review, we thoroughly discussed the influence that electrolytes might induce on eCO(2)R from three perspectives, namely, pH, cations, and anions. Both experimental and theoretical efforts are included, along with the hypothesis on the fundamental working mechanism. We also highlighted the challenges associated with understanding and harnessing the electrolyte effect, as well as theoretical modeling and machine learning as interesting directions worthy of further research and exploration. We believe that this Review can help to shed light on the rational design and optimization of electrolytes, thereby facilitating the activity tuning and selectivity steering of eCO(2)R to valuable C2+ products.