Bi has drawn attention in catalyzing the electrochemical CO2-to-formate conversion due to promising selectivity and low cost, but the process suffers from low activity. Herein, we introduce nitrogen-doped carbon (NC) support with hydrophobicity modification to enhance the activity of a binder-free Bi2O3 electrode. Formate partial current on the NC supported Bi2O3 electrode almost doubles compared to Bi2O3 on unmodified support. Furthermore, the hydrophobicity modification with polytetrafluoroethylene (PTFE) significantly extends the stability of NC supported Bi2O3 by diminishing flooding. It also maintains >90% formate selectivity at a broad potential range from −0.87 to −1.27 V (vs. RHE) and shows a formate partial current density of −100 mA cm−2 at −1.37 V (vs. RHE) in 0.5 M KHCO3. The improvement is attributed to the synergetic effects of the hydrophilic active sites and the hydrophobic PTFE modified NC support. The unique structure promotes the reactants transport and thus maximizes the active site utilization at the triple-phase interface. This facile microenvironment regulation can be extended to other applications involving gaseous-aqueous phases.