<p>The electrochemical reduction of CO₂ (CO₂RR) to formic acid (HCOOH) is both economically viable and technically promising for industrial applications. However, current catalysts for HCOOH production exhibit substantial overpotentials to achieve industrial production rates. This limitation stems from the relatively low activity for solvent–water activation of high HCOOH-selective catalysts, e.g., Bi and Sn, which in turn leads to a high energy barrier for the hydrogenation of CO₂-to-*HCOO intermediates. Here, we report the exclusive CO₂-to-formate conversion on Zn, a well-known CO-selective catalyst with moderate hydrogen evolution activity, via atomic indium oxide domain (In₁O₆) functionalization. The catalyst demonstrates Faradaic efficiencies for HCOOH exceeding 90% across a wide voltage range. Impressively, it required merely −1.49&#xa0;V vs. RHE to deliver an activity of −1000&#xa0;mA&#xa0;cm⁻² with current efficiency of ~ 94%, showing much improved cathodic energy efficiency (~ 45%) compared with that of conventional alternatives. Mechanistic studies revealed that the incorporation of atomic In₁O₆ domains into Zn shifts the CO₂ adsorption configuration on the surface from bent to linear, thereby driving the selectivity inversion from CO to HCOOH. In₁O₆ domains further modulate the electronic structure of Zn and its adsorption properties, resulting in highly active Zn^δ+ sites, which are conducive to the stabilization of *HCOO intermediates and yield enhanced activity. This work establishes the concept of bridging-atom-mediated single-atom modulation, offering new insights into the design of efficient and sustainable systems for CO₂ electrolysis and beyond.</p>