(Digital Presentation) Fabrication and Electrochemical Characterization of Inkjet Printed IrO2 Electrodes for Water Electrolysis
Authors: Shnaiter Marwah , Graves John , Bogush Anna , Lan Rong 
Published: July 2022

Water electrolysis is believed to be one of the most promising technologies to produce green hydrogen. However, the current challenge in commercialising this technology is the high relative cost. According to a recent report on cost breakdown of Polymer Electrolyte Membrane (PEM) electrolyser [1], the cell stack contributes to 35% - 45% of the total cost. Catalyst materials on the electrodes are believed to be the primary areas for innovation and cost reduction in PEM electrolysers. Several approaches have been applied to reduce the stack cost, with a focus on reducing material usage while enhancing the performance of PEM electrolysers. This project aims to reduce catalyst loading on the anode of PEM water electrolyser while maintaining high performance, through developing an inkjet printing technique to create a thin, porous and active catalyst layer. Conventional catalyst fabrication techniques such as spray coating produce large amount of material waste and non-homogenous distribution on the surface [2]. Inkjet printing will provide controlled catalyst loading, ensuring well catalyst distribution, creating porous structure, and having the ability to create patterned electrodes [3].

Due to its high activity, Iridium Oxide (IrO2) is selected as the catalyst. The ink was formulated to be compatible with the printing requirement, with 7.5 wt% of IrO2 powder, 7.9 wt% of Nafion, and 84.5 wt% of solvents mixture of Isopropanol and Propylene Glycol. Full coverage of the catalyst on the Titanium substrate was proven by Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX). The effect on varying the number of printed layers was analysed in terms of catalyst loading and activity to show a linear increase in activity with the number of layers. Moreover, electrochemical performance was inspected using cyclic voltammetry in a 3-electrodes cell. The printed electrodes showed comparable stability to conventional electrodes. Electrochemical surface area (ECSA) was higher for the 10-layered electrodes as compared to the 2-layered electrodes indicating higher catalyst utilisation. Printed electrodes showed activity of 300 mA/mg IrO2 with ECSA of 225 cm2 at reduced catalyst loading of 0.8 mg IrO2/cm2. These results outperform conventionally fabricated electrodes by spray and decal transfer coatings [4].

References

[1] A. T. Mayyas, M. F. Ruth, B. S. Pivovar, G. Bender, and K. B. Wipke, “Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers,” NREL/TP-6A20-72740, 1557965, Aug. 2019. doi: 10.2172/1557965.

[2] W. Qing, F. Liu, H. Yao, S. Sun, C. Chen, and W. Zhang, “Functional catalytic membrane development: A review of catalyst coating techniques,” Adv. Colloid Interface Sci., vol. 282, p. 102207, Aug. 2020, doi: 10.1016/j.cis.2020.102207.

[3] J.-J. Chen, G.-Q. Lin, Y. Wang, E. Sowade, R. R. Baumann, and Z.-S. Feng, “Fabrication of conductive copper patterns using reactive inkjet printing followed by two-step electroless plating,” Appl. Surf. Sci., vol. 396, pp. 202–207, Feb. 2017, doi: 10.1016/j.apsusc.2016.09.152.

[4] Z. Xie et al., “Optimization of catalyst-coated membranes for enhancing performance in proton exchange membrane electrolyzer cells,” Int. J. Hydrog. Energy, vol. 46, no. 1, pp. 1155–1162, Jan. 2021, doi: 10.1016/j.ijhydene.2020.09.239.