Polyelectrolyte engineering for acidic CO2 electroreduction.

Acidic electrocatalytic CO2 reduction (eCO2R) offers a promising route to overcome the carbon losses inherent to conventional neutral and alkaline systems. However, its development remains limited by sluggish CO2 activation, competing hydrogen evolution, and poor operational stability. In this Review, we highlight polyelectrolyte engineering as an effective strategy to regulate the catalyst/electrolyte interface in acidic eCO2R. We summarize recent advances in cation-exchange and anion-exchange polyelectrolytes, as well as their composite architectures, focusing on their roles in enhancing CO2 enrichment and activation, suppressing H+ transport and thereby inhibiting hydrogen evolution, modulating the interfacial water structure, and regulating cation effects. We also discuss key challenges and emerging opportunities for designing polyelectrolytes that simultaneously enable efficient, selective, and durable acidic eCO2R.