The electrocatalytic carbon dioxide reduction reaction (eCO_2RR) powered by renewable energy can convert CO_2 into high-value chemicals and fuels. It is a viable solution to address the sharp increase in atmospheric CO_2 concentration and global warming. However, in traditional neutral or alkaline electrolytes, eCO_2RR suffers from severe carbon loss, resulting in a theoretical single-pass carbon conversion elficiency (SPCE) of less than 50%, and the regeneration of the electrolyte requires additional energy. Acidic electrolytes can effectively solve the carbon loss issue, achieving a theoretical SPCE of 100%, which has attracted widespread attention worldwide. Nevertheless, most previous studies focused on catalyst optimization, with insufficient emphasis on optimizing solid-liquid-gas interfaces such as gas diffusion electrodes (GDEs), electrolytes, and proton membranes. These factors influence the selectivity, stability, and energy eficiency of eCO_2RR. In this study, we systematically optimized the three-phase interface (solid, liquid, and gas) of the acidic eCO_2RR, achieving a fara.daic efficieney for CO ( FE_CO) of over 90% at a current density of 100 mA·cm^-2 and a cell voltage of less than 5 V, with stable operation for 110 hours. Finally, we scaled up the electrode area to 100 cm^2, exploring the impact mechanism of process scale-up, and proposing a new intermittent operation strategy. This research on interface optimization and process scale-up of acidic eCO_2RR is expected to pro-vide a theoretical foundation for its potential industrial applications.