Varipore™: A Powerful Manufacturing Platform for Fuel Cell and Electrolyzer Applications
Authors: Serov Alexey , Lubers Alia , McCool Geoffrey , McKinney Samuel , Romero Henry , Zulevi Barr 
Published: February 2020

There are an increasing number of published works devoted to development of Platinum Group Metal-free (PGM-free) electrocatalysts for both the anode [1] and cathode [2] sides of membrane electrode assembly (MEA). Several laboratory scale methods were used for preparation of cathodic electrocatalysts based on pyrolysis of chelate compounds [3], Metal-Organic Frameworks (MOFs) [4], graphene-like derivatives [5] and small organic molecules [6]. Other classes of electrocatalysts for fuel cells (FCs) and electrolyzers (ECs) application based on PGM supported or in a black form were comprehensively studied by many research groups [7]. With a significant progress in improving stability, activity and durability of FC and EC catalysts the need in universal, scalable and reproducible manufacturing approach was arisen. Pajarito Powder (PP) developed such an approach trademarked as a VariPore™ method (Figure 1).

Figure 1. Schematics of VariPore™ manufacturing method
The method is based on licensed intellectual property (IP) from several academic institutions, internal Pajarito’s know-hows and PP’s proprietary innovations. It can be described as synthetic approach utilized different pore and particle formers (hard and soft templating) in order to control morphology (pore size distribution, particle size distribution, surface area), chemical composition (surface and bulk chemistry) and physical properties (electrical and thermal conductivity, density and other). At different stages of method development, it was successfully applied for the preparation at scale: PGM-free ORR electrocatalysts [8,9], unsupported PGM electrocatalysts [10], Engineered Catalysts Supports (ECSs, publication is in preparation) and materials for Anion Exchange Membrane (AEM) fuel cells and electrolyzers [11, 12].
The general approach of VariPore™ is based on infusion of pore and particle formers (silica, magnesia and other templates) with precursors of final materials (PGM salts, base metals salts, organic compounds and other) followed by chemical transformation of these precursors into the supports or catalysts. Soft chemical reduction (formic acid), strong chemical reduction (hydrazine) and high temperature treatment (inert, reducing or reactive) were successfully optimized in order to produce mentioned above classes of materials for FC and EC applications.
This presentation will describe the application of VariPore™ for the preparation of ECS materials, PGM-free catalysts for PEM and AEM fuel cells, CO2 electroreduction (CO2ER), Direct Methanol Fuel Cells (DMFC) and novel classes of electrocatalysts for AEM electrolyzers.

Acknowledgement:
This work was supported by US DOE EERE grant DE-EE0008419 "Active and Durable PGM-free Cathodic Electrocatalysts for Fuel Cell Application" PI: Alexey Serov.
References
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Figure 1