CHEMICAL ENGINEERING TRANSACTIONS VOL. 41, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Simonetta Palmas, Michele Mascia, Annalisa Vacca Copyright © 2014, AIDIC Servizi S.r.l., ISBN 978-88-95608-32-7; ISSN 2283-9216 Implementation of Cobalt Clathrochelates in Polymer Electrolyte Water Electrolysers for Hydrogen Evolution Pierre Millet*, Caroline Rozain, Angel Villagra, Anuradha Ragupathy, Alireza Ranjbari, Michel. Guymont Université Paris-Sud, ICMMO, Bât. 410, 91405 Orsay cedex France pierre.millet@u-psud.fr The purpose of this communication is to provide a review of main electrocatalysts used in PEM water electrolysis cells for both the hydrogen and oxygen evolution reactions, with a special emphasis on nanoscale structures including unsupported and supported nano-particles as well as substrate-adsorbed molecular compounds. Performances obtained using conventional platinum group metal electrocatalysts (platinum for the hydrogen evolution reaction and iridium dioxide for the oxygen evolution reaction) are compared to those measured on non-conventional membrane-electrode assemblies in which platinum has been replaced by cobalt-containing clathrochelates. Results on both performance and stability issues are reported. Some perspectives for enhanced performances of PEM water electrolysis cells are also discussed. 1. Introduction From a historical perspective, the concept of solid polymer electrolyte (SPE) cell was introduced in the early 1950s, at the dawn of the US space program, and was considered at that time as an innovative approach for the development of a new generation of H 2 /O 2 fuel cells that could operate efficiently in zero- gravity environments (Grubb, 1959). In the 1960s, innovative perfulorosulfonated ionomers became commercially available and this open the way to technological development of Polymer Electrolyte Membrane (PEM) water electrolysers. Electrolyzers (up to several tens of H 2 normal cubic meters per hour or Nm 3 H 2 /h) were first developed for the production of oxygen of electrolytic grade in anaerobic environments such as submarines. Gradually, concern about climate change offered new market opportunities for the technology. PEM water electrolysis is now considered as a key process of increasing interest for the development of a hydrogen refuelling infrastructure, but also for operation of power grids in a more flexible way and for the large scale storage of renewable energy sources (so-called hydrogen economy in which hydrogen is used as an energy carrier). In conventional PEM water electrolysers (Millet, 2011), platinum is used at the cathode for the hydrogen evolution reaction (HER) and iridium or iridium oxide is used at the anode for the oxygen evolution reaction (OER). Although the relative cost share of platinum group metal (PGM) electrocatalysts is limited (up to a few percent) in industrial systems, there is a need to anticipate future cost reduction requirements and to develop alternative low-cost electrocatalysts that could sustain significantly high operating current densities (in the multi Amp.cm 2 range) and would remain stable on the long-term (for market implementation, operation in the 10 4 -10 5 hours range of operation is desirable). The purpose of his paper is to review the situation and discuss some alternative solutions. 2. Experimental section A schematic diagram, showing the cross-section of a PEM water electrolysis cell, is pictured in figure 1. This is a symmetrical and compact structure: the total thickness usually ranges between 5 and 7 mm. The active electrochemical cell component at the centre of the cell is the membrane – electrode assembly (MEA), which separates the anodic and cathodic compartments. The MEA is usually made a thin (0.15 – DOI: 10.3303/CET1441055 Please cite this article as: Millet P., Rozain C., Villagra A., Ragupathy A., Ranjbari A., Guymont M., 2014, Implementation of cobalt clathrochelates in polymer electrolyte water electrolysers for hydrogen evolution, Chemical Engineering Transactions, 41, 325-330 DOI: 10.3303/CET1441055 325