Development of Proton Exchange Membrane Water Electrolyzers with Low Catalyst Loadings and Recombination Layers By Reactive Spray Deposition Technology

Abstract

Hydrogen is an important material for many different applications including materials processing, oil refining, ammonia production, energy storage, among many others. In commercial development since the 1950s, proton exchange membrane water electrolyzers (PEMWEs) have been identified as a green source of high-purity hydrogen which can be utilized for many applications [1]. While hydrogen produced by PEMWEs has shown significant promise as a clean hydrogen source for fuels or energy storage, there are a few technical challenges that need to be addressed to allow for its widespread use. One such challenge involves hydrogen crossover. In operation, hydrogen that is formed in the highly pressurized (~400 psi) cathode can diffuse back through the proton exchange membrane and into the anode chamber where oxygen is being formed as a result of the water splitting reaction [2]. This can lead to both performance and safety concerns. With the lower flammability limit (LFL) of hydrogen in oxygen around 4 vol%, typical operating conditions of a PEMWE are set such that the hydrogen concentration in the anodic stream does not approach 50% of the LFL. In order to ensure operation of the PEMWE at the desired operating conditions, mitigation strategies have been implemented to reduce the hydrogen crossover. One such mitigation strategy recently published by Klose, Trinke et al. has shown that introducing a platinum recombination layer within the membrane can significantly reduce the hydrogen crossover [3]. This work will examine PEMWEs with recombination layers developed entirely by Reactive Spray Deposition Technology (RSDT). The RSDT process provides significant advantages for recombination layer development as the small platinum nanoparticles (~2nm diameter) produced by RSDT allows for a significant reduction of hydrogen crossover with low loadings while also being able to optimize the thickness of the Nafion® insulating layer for the recombination layer to optimize the reduction of gas crossover while minimizing Ohmic losses. Platinum recombination layers will be able to reduce the hydrogen crossover to less than 10% of the lower flammability limit. In addition, the RSDT will be able to deposit low-loaded Pt/C cathodes and IrOx anodes which will assist in the cost reduction of the PEMWE without negatively effecting the performance of the electrolyzer. These low-loaded PEMWE samples developed by RSDT will allow for a cost-effective PEMWE with reduced gas crossover which will allow for more flexible operating conditions.