• Reducing catalyst loading from 10 to 1.685 mg·cm−2 and increasing current density in concentrated bicarbonate solutions boosts formate faradaic efficiency to 88% at −30 mA·cm−2, while lowering costs and suppressing hydrogen evolution.
• Applying Nafion as a surface coating rather than mixing it into the ink improves formate production, but binder-free systems still outperform due to the intrinsic activity of Sn catalysts.
• PVDF binder shows promise for formate production (72% FE at −30 mA·cm−2) despite blocking active sites, owing to its stability, strength, and conductivity.
• The study provides practical guidelines for optimizing catalyst ink formulations and binder use to enhance CO2-to-formate conversion, supporting cost-efficient high-current-density operations.