Electrochemical CO₂ reduction is an essential direction of direct CO₂ utilization. Increasing the product selectivity and decreasing the cost of product separation are critical for large-scale application of electrochemical CO₂ reduction (ECO₂R). While numerous studies optimize the properties of electrocatalysts for CO₂ reduction, tuning the composition of electrolyte can also shift the product distribution. So far, most of the studies are focused on conventional low-concentration aqueous electrolyte. We hypothesize that highly concentrated aqueous electrolytes can tune the microenvironment of the catalyst/electrolyte interface and improve product selectivity.