Control of the Ionomer Contents in the Electrode Catalyst Layer for Enhanced Performance of Methanol–Water Electrolyzers for Hydrogen Production

Methanol–water electrolysis technology, which electrochemically produces hydrogen using methanol instead of water, has received significant attention given that the substantial amount of power required by conventional water electrolysis can be drastically reduced when using it. This study investigates the electrochemical performance and microstructural characteristics of methanol–water electrolyzers according to the ionomer-to-carbon (I/C) ratio range of 0.5–2.0 in electrode catalyst layers. The lowest voltage at the same current density is observed at an I/C ratio of 1.5 at the anode. When the I/C ratio was 2.0, the voltage was observed to be approximately 25% higher than that at an I/C ratio of 1.5. A microstructural analysis shows a decrease of the specific surface area due to catalyst agglomeration at I/C ratios higher than 1.5. The results of the BET analysis showed a decrease in the surface area with an increase in the I/C ratio. Furthermore, when the I/C ratio exceeds 1.5, separated layers of excessive amounts of ionomer are observed, possibly blocking the electron conduction pathways in the electrode catalyst layer. The energy conversion efficiency of the developed methanol–water electrolyzer was assessed in an current density range of 0.08–0.80 A cm⁻², demonstrating values between 81.4% and 92.4%.