Ultra-low loading of IrO2 with an inverse-opal structure in a polymer-exchange membrane water electrolysis

In this study, an iridium oxide (IrO2) inverse-opal membrane-electrode assembly (inverse-opal MEA) was fabricated via the decal-transfer method for an anode in polymer-electrolyte membrane water electrolysis (PEMWE) to decrease the loading of the noble catalyst. Electrodeposition parameters including current and total number of cycles were investigated to achieve the IrO2 inverse-opal electrode. The inverse-opal MEA with ultra-low loading exhibited outstanding performance that exceeded or was comparable to that obtained in other PEMWE studies. Additionally, it exhibited higher performance and lower ohmic and charge-transfer resistance when compared with that of commercial IrO2. Furthermore, the performance corresponded to the highest mass activity reported to date since the loading in the inverse-opal MEA was ultra-low. This was because the inverse-opal structure improved electron transfer owing to the interconnected pores and increased the surface area due to high porosity, thereby leading to the enhanced utilization of the catalyst.