A system for producing gas streams for use in synthetic fuel production through CO2 capture and water splitting is disclosed. The system includes a CO2 capture device configured to receive a CO2-containing stream and including an aqueous alkaline solution. The alkaline solution includes hydroxide and/or carbonate ions. The CO2 capture device generates a carbon-rich solution when the alkaline solution absorbs CO2. The carbon-rich solution includes carbonate and/or bicarbonate ions. The system also includes an electrolyzer fluidically coupled to the CO2 capture device, and defining a volume including an anode region having an anode, and a cathode region having a cathode. The volume includes an electrolyte solution having a pH gradient generated by an electric current, causing the electrolyte solution to be acidic in the anode region and alkaline in the cathode region. The carbon-rich solution is received into the electrolyzer. The electrolyzer generates hydrogen, oxygen, and CO2 streams.