Effective and Durable Recombination Layers for Hydrogen Crossover Mitigation in Proton Exchange Membrane Water Electrolyzers

Abstract

The Hydrogen Economy (HE) is the economy of the near future and is the only viable alternative to the current fossil fuel-based economy. This future green economy will eliminate the greenhouse gas emissions and stop the imminent global warming and climate change. The HE implementation relies on the development of zero-carbon emission technologies for Hydrogen (H2) production. “Green” hydrogen can be produced in large scale by integration of water electrolyzers (WEs) with renewable energy sources. Currently, the proton exchange membrane water electrolyzers (PEMWEs) are considered as the most advanced WEs that can be integrated with solar panels and wind turbines to produce large quantities of green H2. The main challenges that the state-of-the-art membrane electrode assemblies (MEAs) for PEMWEs are currently facing are: (i) high cost because of the high platinum group metals (PGM) loadings in their catalysts layers (2-3 mgPGM/cm2 in each electrode) and time consuming and expensive multi-step fabrication processes associated with their manufacturing; (ii) limited durability caused by the instability of the catalysts and the materials, and (iii) safety concerns associated with the hydrogen gas crossover and the absence of technologies that can effectively mitigate and keep it below the safety level of the lower flammability limit (LFL) [1, 2, 3].In this paper, we demonstrate the capabilities of the reactive spray deposition technology (RSDT) to fabricate MEAs with one order of magnitude lower PGM catalyst loadings in their electrodes, and catalytic recombination layers integrated in the volume of the MEAs that effectively suppress the H2 crossover. The RSDT is a flame assisted method that combines the catalysts synthesis and deposition directly on the PEM membrane in one-step, which results in fast and facile fabrication of large scale MEAs [4, 5, 6]. RSDT-fabricated recombination layers (RLs) demonstrated effective reduction of H2 crossover from 30-50% of the LFL to less than 10% of the LFL when operating at current densities between 0.58 A/cm2 and 1.86 A/cm2. These recombination layers are with Pt loading of only 0.02 mgPt/cm2 and are incorporated in the volume of the membrane of the RSDT-fabricated MEAs. The MEAs with an active area of 86 cm2 and low catalyst loadings (0.3 mgIr/cm2 in the anode and 0.2 mgPt/cm2 in the cathode) have been tested for over 5000 hrs, and it was found that the H2 crossover increased to about 20 % of the LFL after 2000 hrs of operation. In order to improve the durability of the RLs, a new design comprised from two RLs separated with thin (10 um) Nafion membrane has been fabricated by the RSDT, and the results from the stability test of 3000 hrs will be presented and discussed in detail at the 242th ECS meeting. https://www.energy.gov/sites/prod/files/2017/05/f34/fcto_myrdd_fuel_cells.pdf https://www.energy.gov/sites/prod/files/2015/06/f23/fcto_myrdd_production.pdf Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach, and S. Thiele, J. Electrochem. Soc., 165, F1271–F1277 (2018).Yu, H., Baricci, A., Bisello, A., Bonville, L., Maric, R., et al. Electrochimica Acta, 247, 1155-1168 (2017).Roller, J., Maric, R., 24(8) December 2015 pp. 1529-1541 (2015).Mirshekari, G., Ouimet, R., Zeng, Z, Yu, H., Bliznakov, S., Bonville, L., Niedzwiecki, A., Errico, S., Capuano, C., Mani, P., Ayers, K., Maric, R. International Journal for Hydrogen Energy, 46(2), 2021, pp. 1526-1539 (2021).