This study demonstrates the electrochemical reduction of CO2 and CO using interface-engineered Au/Ti electrodes. Direct adsorption of CO and indirect processes in CO2 conditions were proposed to form surface CO. Surface H was formed from H+/H2O. Mimicking Fischer–Tropsch synthesis between surface CO and H resulted in the production of CH4 and hydrocarbons (CnH2n and CnH2n+2, n = 2–7). Faradaic efficiency of CO increased with increasing Au coverage and reached 38%. In CO2-saturated KHCO3, long-chain hydrocarbon production was observed on Au/Ti electrodes with low Au coverage. In CO2 and CO-saturated phosphate electrolytes, higher Au coverage resulted in higher production of long-chain hydrocarbons. The ratio of alkanes to alkenes increased with increasing Au coverage but decreased with applied potential. The study provides insights into interface engineering, electrochemical long-chain hydrocarbon production, and C−C coupling mechanisms.