Achieving industrial electrochemical CO2 reduction necessitates the strategic design of electrocatalysts with high activity, superior selectivity, and excellent stability. Herein, we developed spatially dispersed copper nanocrystals supported by polyaniline (PANI-CuNCs) for electrochemical CO2 reduction, achieving a faradaic efficiency of 68.6% ± 2.2% toward methane at −300 mA cm−2. The chelation of the Cu precursor within the oxidized emeraldine base (EB) is crucial for forming isolated CuNCs. The PANI substrate facilitates proton shuttling to Cu(111) sites, enhancing methane production by promoting protonation and reducing ∗CO coverage. In situ Raman and theoretical calculations show that PANI improves CO2 adsorption and activation by creating a hydrophilic environment, highlighting its potential for industrial CO2 reduction electrocatalysis. Our work introduced a promising strategy that utilizes polymers as substrates to prepare well-dispersed NCs for electrocatalysis, highlighting the potential of such systems in advancing the field of industrial electrochemical CO2 reduction.