Pathways to Ultra-Low Platinum Group Metal Catalyst Loading in Proton Exchange Membrane Electrolyzers
This is a peer reviewed Accepted Manuscript of an article published in its final form in Catalysis Today, available at: https://doi.org/10.1016/j.cattod.2015.10.019
Abstract
Hydrogen is one of the world's most important chemicals, with global production of about 50 billion kg/year. Currently, hydrogen is mainly produced from fossil fuels such as natural gas and coal, producing CO2. Water electrolysis is a promising technology for fossil-free, CO2-free hydrogen production. Proton exchange membrane (PEM)-based water electrolysis also eliminates the need for caustic electrolyte, and has been proven at megawatt scale. However, a major cost driver is the electrode, specifically the cost of electrocatalysts used to improve the reaction efficiency, which are applied at high loadings (>3 mg/cm2 total platinum group metal (PGM) content). Core-shell catalysts have shown improved activity for hydrogen production, enabling reduced catalyst loadings, while reactive spray deposition techniques (RSDT) have been demonstrated to enable manufacture of catalyst layers more uniformly and with higher repeatability than existing techniques. Core-shell catalysts have also been fabricated with RSDT for fuel cell electrodes with good performance. Manufacturing and materials need to go hand in hand in order to successfully fabricate electrodes with ultra-low catalyst loadings (<0.5 mg/cm2 total PGM content) without significant variation in performance. This paper describes the potential for these two technologies to work together to enable low cost PEM electrolysis systems.