Electrochemical reduction of carbon dioxide (CO2R) driven by renewable electricity is a promising strategy to mitigate CO2 emissions while generating valuable chemicals and fuels. Multicarbon products (e.g., ethylene, ethanol) produced via CO2R are particularly attractive due to their high economic value and market demand. Performing CO2R in acidic media represents a promising approach to mitigate carbon loss observed in alkaline and neutral electrolytes, realizing high CO2 utilization.[1] However, the local acidic condition in the vicinity of catalysts in acidic electrolyte favors hydrogen evolution reaction, diminishing CO2 reduction.[2] Enabling CO2 reduction to multicarbon product with high selectivity remains challenging. Our results show that by engineering the catalyst and catalyst microenvironment (ions/gas transport), the selectivity and productivity towards multicarbon product are remarkably enhanced.[3-5]