Abstract: Electrochemical CO₂ reduction to CO offers a promising route for carbon recycling driven by renewable electricity. However, copper-based catalysts generally yield a broad range of reduction products, making selective CO generation challenging. Surface modification provides an opportunity to redirect product distributions without replacing the copper catalyst platform. A series of GeO₂-modified Cu catalysts, denoted as CuGe-x, were prepared via physical mixing, ultrasonication, and stirring. Structural characterization, electrochemical measurements, product analysis, in situ infrared spectroscopy, and density functional theory (DFT) calculations were combined to investigate the relationship between GeO₂ modification and catalytic performance. In a flow cell containing 0.5 mol/L KOH, CuGe-3 maintained a CO Faradaic efficiency above 70% across a wide current-density range of 50–400 mA·cm⁻². At 100 mA·cm⁻², the CO Faradaic efficiency remained at approximately 80% over 10 h of continuous electrolysis. Compared with the broad product distribution observed for pure Cu, GeO₂ modification favored CO production while suppressing multicarbon products. Linear sweep voltammetry showed a total current density of approximately −600 mA·cm⁻² at −1.0 V versus the reversible hydrogen electrode, which was approximately twice that of pure Cu. The double-layer capacitance increased from 4.7 to 7.7 mF·cm⁻², indicating a larger electrochemically active surface area under the same measurement conditions. Post-reaction characterization revealed the retention of the catalyst morphology and detectable Ge species, consistent with the sustained electrochemical performance. Combining DFT calculations with structural characterization and in situ spectroscopy provided a basis for interpreting these observations. The shift in the Cu 2p binding energy indicated a modified local electronic environment, while Cu LMM spectra identified mixed Cu⁰/Cu⁺ species. Enhanced *COOH infrared signals were consistent with the facilitated formation of this intermediate. In the computational models, the free energy for *COOH formation decreased from 0.257 to 0.174 eV, whereas that for *COCHO formation increased from 0.411 to 0.523 eV. Together with local charge redistribution, these trends support a shift in the reaction pathway toward CO generation. Interfacial Cu^δ+ sites associated with the metallic Cu matrix are therefore proposed as potential active centers, rather than definitively established unique sites. GeO₂ modification redirects Cu-based CO₂ reduction toward CO while maintaining high selectivity across a broad current-density range. The combination of high selectivity and high current response distinguishes CuGe-3 within the investigated catalyst series. The combined evidence links the observed performance to changes in the local electronic environment and intermediate-formation thermodynamics, providing a basis for designing modified copper catalysts with controlled product distributions.