Through interface engineering and content control strategy, a PdBi bimetallic interface structure was constructed for the first time to selectively convert CO₂ to formate with a remarkably high Faraday efficiency (FE_formate) of 94% and a partial current density (j_formate) of 34 mA·cm⁻² at −0.8 V vs. reversible hydrogen electrode (RHE) in an H-cell. Moreover, the PdBi interface electrocatalyst even exhibited a high current density of 180 mA·cm⁻² with formate selectivity up to 92% in a flow cell and could steadily operate for at least 20 h. Electrochemical in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) confirmed that the PdBi interface could greatly weaken the adsorption of *CO intermediates due to electronic and geometric effects. Density functional theory (DFT) calculations also established that the PdBi interface regulated the CO₂-to-formate pathway by reducing the energy barrier toward HCOOH and largely weakening the adsorption of *CO intermediates on the catalyst surface. This study reveals that the unique PdBi bimetallic interface can provide a novel platform to study the reaction mechanism through combining in-situ ATR-SEIRAS and DFT calculations.