Minireview and Outlook of Salt Precipitation in CO2 Electrolysis

Abstract CO2 electrolysis has progressed rapidly toward industrially relevant current densities, but its practical deployment is increasingly limited by reactor-level instabilities. Specifically, salt precipitation has emerged as a critical yet not well-understood challenge in high-rate CO2 electrolysis. Recent studies show that this phenomenon is governed not simply by bulk electrolyte composition, but by coupled interfacial properties including local alkalinity, cation migration and water distribution. The resulting bi(carbonate) accumulation can lead to supersaturation within the confined pore structures of the gas diffusion layer and subsequently salt nucleation and precipitation. These deposits reduce CO2 mass transport and eventually induce flooding that substantially compromise electrolyzer performance. In this minireview, we summarize the mechanistic origins, spatial distribution, and performance consequences of salt precipitation in CO2 electrolysis. We further assess emerging diagnostic tools and outline salt precipitation mitigation strategies towards the development of stable CO2 electrolyzers.