Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids

The electrocatalytic CO₂ reduction reaction (CO₂RR) is a sustainable route for converting CO₂ into value-added fuels and feedstocks, advancing a carbon-neutral economy. The electrolyte critically influences CO₂ utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO₂RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C₂₊) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO₂RR over the competitive hydrogen evolution reaction (HER) and improve long-term stability. This review examines progress in the acidic CO₂RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO₂RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO₂RR technology, offering guidance for developing practical systems for the carbon-neutral community.