Sputtering Pt on Low-Loading Iridium-Based Anode to Improve Both Cell Performance and Gas Permeation Issue in PEM Water Electrolysis
Authors: Phan Thien Thanh , Rahman MD Mizanur , Phan Thien , Islam Jahowa , Cho Hyun-Seok , Kim MinJoong , Lee Chang-Soo , Lee Jae-Hun , Lee Sae-Chan 
Published: November 2022

Polymer electrolyte membrane (PEM) water electrolysis is one of the most promising technologies which can integrate with renewable sources to produce sustainable hydrogen energy. Thin membranes were preferred for making membrane electrode assembly (MEA) for the PEM electrolyzer to increase cell efficiency. However, these membranes suffered from significant gas permeation consequently resulting in an explosion by the combination of hydrogen and oxygen, especially in the high-pressure operation. Many publications employed platinum as a recombination catalyst for reducing hydrogen concentration in the oxygen product stream to ensure safe operation [1-4]. Beside, Pt could be coated on oxidated Ti porous transport layer (PTL) to improve contact resistance between Iridium-based electrode and PTL [5]. In this work, a thin layer of platinum was sputtered on the surface of a low-loading anode (0.5 mgIr/cm2). Three MEAs prepared from commercial hydrous IrOx catalyst with 3 different loadings (1 mgIr/cm2, 2 mgIr/cm2and 3 mgIr/cm2) were used as reference. SEM images of Pt-sputtered MEA showed that the Pt layer had a thickness of approximately 80 nm corresponding to a loading of 0.4 mgPt/cm2. The electrochemical performance of Pt-sputtered MEA was significantly higher than that of bare MEA with 1 and 2 mgIr/cm2. The better performance of MEA with the presence of Pt is due to the improvement in contact resistance between the catalyst layer and PTL, in which lower HFR can be seen. In addition, its performance was comparable to high-loading MEA, while the total amount of precious metal was much lower (0.9 and 3 mg/cm2, respectively). The sputtered MEA also exhibited a slight difference in kinetic resistance compared to pristine MEA. On the other hand, the MEA with the addition of Pt shows a lower concentration of hydrogen in the oxygen product stream compared to pristine MEA at ambient pressure.
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[2] N. Briguglio, F. Pantò, S. Siracusano, and A. Aricò, "Enhanced performance of a PtCo recombination catalyst for reducing the H2 concentration in the O2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure," Electrochimica Acta, vol. 344, p. 136153, 2020.
[3] S. Garbe, E. Samulesson, T. J. Schmidt, and L. Gubler, "Comparison of Pt-Doped Membranes for Gas Crossover Suppression in Polymer Electrolyte Water Electrolysis," Journal of The Electrochemical Society, vol. 168, no. 10, p. 104502, 2021.
[4] A. Stähler, M. Stähler, F. Scheepers, W. Lehnert, and M. Carmo, "Scalable Implementation of Recombination Catalyst Layers to Mitigate Gas Crossover in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 169, no. 3, p. 034522, 2022.
[5] M. Bernt et al., "Effect of the IrOx Conductivity on the Anode Electrode/Porous Transport Layer Interfacial Resistance in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 168, no. 8, p. 084513, 2021.

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