1 FAILURE OF PEM WATER ELECTROLYSIS CELLS: CASE STUDY INVOLVING ANODE DISSOLUTION AND MEMBRANE THINNING Dzhus, K.A. 1 , Grigoriev, S.A. 1 , Bessarabov, D.G. 2 , Millet, P. 3 , Korobtsev, S.V. 1 and Fateev, V.N. 1 1 Center of Physical and Chemical Technology, National Research Center “Kurchatov Institute”, Kurchatov sq. 1, Moscow, 123182, Russia, grig@hepti.kiae.ru 2 DST HySA Infrastructure Centre of Competence, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa, Dmitri.Bessarabov@nwu.ac.za 3 Institut de Chimie Moléculaire et des Matériaux, UMR CNRS n° 8182, Université Paris Sud, bât 410, Orsay, 91405 Cedex France, pierre.millet@u-psud.fr ABSTRACT Polymer electrolyte membrane (PEM) water electrolysis is an efficient and environmental friendly method that can be used for the production of molecular hydrogen of electrolytic grade using zero- carbon power sources such as renewable and nuclear. However, market applications are asking for cost reduction and performances improvement. This can be achieved by increasing operating current density and lifetime of operation. Concerning performance, safety, reliability and durability issues, the membrane–electrode assembly (MEA) is probably the weakest cell component. Most performance losses and most accidents occurring during PEM water electrolysis are usually due to the MEA. The purpose of this communication is to report on some specific degradation mechanisms that have been identified as a potential source of performance loss and membrane failure. An ageing test has been performed on a MEA by applying galvanostatic pulses. Platinum has been used as electrocatalyst at both anode and cathode in order to accelerate degradation rate by maintaining higher cell voltage and higher anodic potential that otherwise would have occurred if conventional Ir/IrO x catalysts had been used. Experimental evidence of degradation mechanisms have been obtained by post-mortem analysis of the MEA using microscopy and chemical analysis. Details of these degradation processes are presented and discussed. 1. INTRODUCTION Hydrogen is an important reactant and energy carrier, especially in view of the so-called “hydrogen economy”. Molecular hydrogen can be obtained from natural hydrocarbons (natural gas, oil and coal), using steam reforming or gasification processes, from water (electrolysis, thermolysis) or from biomass. Electrolysis (of brine or water) is a simple and mature way of producing hydrogen of electrolytic grade [1]. However, the world hydrogen production by electrolysis accounts to only approximately 4% of the total world production [2]. And water electrolysis, which is more specifically considered in this paper, to less than 1%. This is mainly due to the fact that the energy required to extract hydrogen from water is about four times larger than the energy required to extract hydrogen from methane. In spite of this handicap, water electrolysis may become a competitive source of hydrogen in the future [3], because of the decline of global fossil fuel reserves, the ever growing availability of electricity from other renewable energy resources and the technology improvement of water electrolysis itself. Over the last years, PEM water electrolysis has received a lot attention. The technology offers high efficiencies at high current densities and low operating temperatures (< 100°C). Compared with the alkaline electrolysis technology, PEM water electrolysis has several advantages, mainly in terms of safety and higher gas purity [4-7]. Decentralized hydrogen production processes by PEM water electrolysis find application in both stationary and transport sectors. PEM water electrolysis (which used to be named as solid polymer electrolyte (SPE) water electrolysis) was first developed by General Electric in the 1960s for spacecraft applications [8]. It rapidly demonstrated significant advantages [9-11] over conventional alkaline water electrolysis. The advantages include (i) the use of significantly less corrosive electrolyte, (ii) a significantly higher hydrogen production capacity, (iii) higher hydrogen purity and (iv) higher efficiency at much higher current densities. Therefore, PEM water electrolysis is considered to be a very promising technique for hydrogen production, that could replace the alkaline process in the long-term. PEM water electrolysis