Development of Recombination Layers to Reduce Gas Crossover for Proton Exchange Membrane Water Electrolyzers 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 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 safety concerns and performance losses. 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 recombination layers designed to reduce gas crossover of PEMWE technology. The Reactive Spray Deposition Technology (RSDT) process was used to deposit small platinum nanoparticles (~2nm diameter) onto a Nafion® 117 membrane as well as deposit a Nafion® insulating layer to create a PEMWE membrane that is able to effectively recombine hydrogen and oxygen to prevent gas crossover. These recombination layers developed by RSDT are shown to reduce the hydrogen crossover to less than 10% of the lower flammability limit. Additional samples will be developed in order to gain an understanding of how recombination layers work, the mechanism required by these layers to recombine the hydrogen and oxygen, and how to better develop and optimize recombination layers.