(1) Prepare catalyst ink
Prepare your catalyst inks via the following recipes:
(5 mg carbon-based catalyst) + (1 mL of ethanol) + (50 uL Nation solution).

Ultrasonicate the mixture solution for 20 min to obtain homogenously dispersed catalyst ink. If your catalyst powder is not electrically conductive enough, you can add conductive agents, e.g., carbon black, CNT, or graphene.

(2) Clean the working electrode
Ensure that the working electrode (glassy carbon) is clean if it was used in the previous experiments. You may grind the working electrode with aluminum powder (of optimal particle size) by drawing "8" periodically.

(3) Prepare the working electrode

Drop cast your catalyst ink on the working electrode (glassy carbon) using a pipette slowly and gently. Dry it in the air or vacuum oven (60oC).

(4) Assembly of the H-Cell

The counter electrode is Pt mesh (or graphite rod).

For a neutral or alkaline solution, the membrane of the H-cell is an anion-ion exchange membrane (AEM). The AEM should be immersed in 1.0 M KOH for at least 1 hr for activation. It is put between the anode chamber and the cathode chamber.

The reference electrode is Ag/AgCl. The Ag/AgCl electrode and working electrode are located in the same chamber.

(5) Collect gas products or check gas leakage
To check if there is a gas leakage, one can use a manual bubbler flowmeter to measure the set rate of a mass flow controller (MFC) and the experimental outflow rate. Measure the bubble's rising level (i.e., volume) and the time required by a time watch.

30 sccm = 30 mL per min.