A complete 5 cm2 Formic Acid electrolyzer. Includes the following components: titanium anode flow field, central compartment, ion exchange media, 904 L stainless steel cathode flow field, catalyst covered electrodes for anode and cathode of 5 cm2 cell, Nafion® membrane, Sustainion® membrane, nuts, bolts, o-rings, gaskets, insulating kit, and electrolyzer testing service.

This electrolyzer converts CO2 into formic acid. It uses a three-compartment design with a anode compartment, a center flow compartment containing a cation exchange media and a cathode compartment where the electrochemical reduction of CO2 to formic acid occurs.

Instructions for use
Initial set up for DM Formic Acid Electrolyzer

• System set up (recommended)
  Typically, the system setup uses one peristaltic pump to circulate DI water (from the reservoir) into the anode chamber at a flowrate of 3 mL/min, and one peristaltic pump to feed DI water (from the reservoir) to the central compartment at a suggested flowrate of 0.065mL/min through the inlets located at the backside of the anode flow field. The flowrate of DI water into central compartment can be adjusted to vary the concentration of produced formic acid. Normally, a slow central compartment flowrate is in favor of the production of higher concentration of formic acid, with decreased Faradaic efficiency. The suggested tubing used is a 1/8” OD, 1/16” ID PTFE tubing. Pure CO2 from cylinder is humidified with water using a bottle humidifier (sold separately) and then fed to the cathode chamber at a flow rate of 30 sccm.
• Tubing Connections
  1. Cathode: remove the nuts from compression fittings and remove black rubber rods from the nuts. Push the tubing (1/8” OD, PTFE) through the nuts, turn the nuts with tubing inside onto the compression fittings. Connect the tubing (PTFE, 1/8”OD) from CO2 humidifier to the compression fitting at the top of cathode (stainless steel flow field), tighten the nuts with fingers only; Connect another tubing (PTFE, 1/8” OD) to the compression fitting at the bottom of cathode, route to the catholyte collector and then to THE EXHAUST. Please note that CO is poisonous and H2 is flammable, so please do not emit or release the cathode gas product into lab or working area.
  2. Anode: Remove the nuts from all the compression fittings and remove the black rubber rods from the nuts. Push the tubing (1/8” OD, PTFE) through the nuts, turn the nuts with tubing inside onto the compression fittings. Follow the labels of the compression fittings and connect all the tubing (1/8” OD, PTFE) accordingly. Tighten the nuts with fingers only.
• Power Connections
  Locate the threaded hole for wire connection on top of the cell (smaller through-hole 8-32 thread). Then connect the ring terminal with the Phillips round head screw (#8). Use this same procedure for both anode and cathode.

Figure 1. The electrolyzer setup	Figure 2. Diagram of the 5 cm2 Formic Acid cell

Cell Testing and Operation
Begin pumping DI water from reservoir to the inlet of the anode chamber at a rate of 3 mL/min and to the inlet of the central compartment at a flowrate of 0.065 mL/min, and feeding CO2 through a bottle humidifier to the inlet of the cathode chamber at a flowrate of 30 sccm. Connect the anode electrical lead (red) and cathode electrical lead (black) to the positive and negative connections, respectively, on the power supply with electric wires/cables (not included). Set the power supply voltage at 4.5 -5.0V and current at 0.5 A (0.1A/cm2) at the beginning of the testing. As the voltage decreases over time and stabilizes, progressively increase the current to 0.6A, 0.8A, 1.0A. The electrolyzer will reach stable conditions in several hours depending on the cell membrane and electrode conditioning. Testing can also be done with potentiostat, but the connections depend on the testing protocol. For long term testing, a reversed polarity treatment at 1.5 V for 30 second is recommended for every ~100 hours to maintain the cell performance.