(1) Assembly Counter Electrode
Stack a piece of brown rubber layer on the PTFE block (named "Counter"). Here, Ni foam is used as the counter electrode for the neutral and alkaline electrodes. It is folded twice to increase the surface area for counter reactions. Connect the other end of Ni foam to a Cu tape. Use Kapton tape to stick Ni foam-Cu tape on the rubber layer. Test if the electrical connection between the Ni foam and Cu tape is well maintained with a multimeter (Ohm mode). Stack another rubber layer on top of the existing one.

(2) Insert Anion Exchange Membrane
Stack an anion exchange membrane (AEM) for a neutral or alkaline electrolyte for the CO2 reduction experiment. Immerse a new AEM in 1.0 M KOH electrolyte for at least 1 hr for activation, otherwise, it will have high resistance. Stack another rubber layer on top of the existing one.

(3)Assembly the Working Electrode
Stack a PTFE block named “Working” subsequently. A Cu sample is stick on the rubber layer with Kapton tape (connect one edge to Cu tape). The Cu side is facing the PTFE block's chamber. FYI: The sample is Cu-coated PTFE, which is fabricated magnetron sputtering.

(4) Assemble the full flow cell
Stack another rubber layer on top of the Cu sample. Put the PTFE block (named "CO2") on top of the rubber layer and use Allen key to tighten the whole cell.

(5) Connecting the gas lines and liquid lines
Connect the CO2 gas lines and the liquid lines for anolyte and catholyte chamber. Use a multimeter (Ohm mode) to measure if the electrical connections of the cell are maintained after the electrolyte immerses the whole cell.

(6) Set up the mass flow controller
Ensure the gas is set between 10-30 sccm and set in the CO2 mode (yellow rectangle in the picture) in the Alicat mass flow controller. Be aware there is a difference between the inflow and outflow directions in the mass flow controller. Flush at least 5 times to get rid of the residual gas in a syringe before use. Withdraw the gas products with the syringe and inject them into GC.