<p>Developing high-efficiency catalyst is crucial for electrochemical conversion of carbon dioxide (CO₂) to high-value products. In the present work, a three-chamber electrolysis cell has been developed for CO₂ reduction to carbon monoxide (CO) in an organic electrolyte, with sodium hydroxide (NaOH) and chlorine (Cl₂) produced as byproducts. In order to improve the performance of the three-chamber electrolyzer, a gallium-based (Ga-based) ternary-porous catalyst (Ga-In₄Ag₉) has been fabricated. During the long-term electrolysis process, Ga-In₄Ag₉ catalyst exhibits good performance toward CO₂ reduction reaction (CO₂RR), the CO partial current density achieves to 139.21&#xa0;mA·cm⁻² at − 2.4&#xa0;V (vs. SHE), with the Faraday efficiency (FE) of CO formation stabled at 92.3%. Density functional theory (DFT) analysis reveals that the position of the d-band center of Ga-In₄Ag₉ is regulated by silver (Ag) atoms, which is beneficial for enhancing the binding ability between the catalyst and the intermediate. Owing to the adsorption of Cl⁻ on the surface of Ga-In₄Ag₉, the reconfiguration of electron density has been altered, which is beneficial for the stabilization of *CO₂⁻ intermediate. This work provides valuable insights for designing Ga-based metal catalysts toward CO₂ electrolysis to produce high-value chemicals.</p> Graphical abstract <p></p>