DMFCs: From Fundamental Aspects to Technology Development A. S. Aricò a, *, S. Srinivasan b and V. Antonucci a a Institute CNR-TAE, Via Salita S. Lucia sopra Contesse, 5, 98126 ± S. Lucia, Messina, Italy b Center for Energy and Environmental Studies, Princeton University, Princeton NJ 08544, US Received 14 February 2001, received in revised form 29 June 2001 I Introduction Direct methanol fuel cells (DMFCs) working at low and in- termediate temperatures (up to 150 C) and employing solid protonic electrolytes have been postulated as suitable systems for power generation in the field of electro-traction [1±6]. DMFCs utilize liquid fuel to deliver continuous power but they have higher utilization efficiencies and intrinsically low- er polluting emissions with respect to internal combustion en- gines. Since transportation represents a significant portion of world energy consumption and contributes considerably to atmospheric pollution, the development of an appropriate fuel cell system is an important issue from both economical and environmental points of view. In order to be competitive within the transport market, the DMFC must be reasonably cheap and capable of delivering high power densities. At present, there are a few challenging problems to the develop- ment of such systems [1±7]. These mainly consist of finding i) electrocatalysts which can effectively enhance the elec- trode-kinetics of methanol oxidation ii) electrolyte mem- branes which have high ionic conductivity and low-methanol cross-over and iii) methanol-tolerant electrocatalysts with high activity for oxygen reduction. Furthermore, all aspects related to fuel cell stack development are of particular rele- vance, in particular, materials and design of cell housing, bi- polar plates, gaskets and stack auxiliaries. All these materials and devices contribute to the final characteristics of practical devices determining their performance, efficiency and cost. At present, the cost of the entire system is mainly determined by the presence of noble metals in the catalyst and the use of Nafion membranes [3±5]. This review deals with both the fundamental and techno- logical aspects of DMFCs. The current status of technology in this field is presented and also the most important technologi- cal challenges and commercialization strategies have been analyzed. A close examination of these aspects indicates that some important problems must still be solved before DMFCs ± [*] Corresponding author, mark.williams@netl.doe.gov Abstract This review paper describes recent developments in both the fundamental and technological aspects of direct methanol fuel cells (DMFCs). Most previous studies in this field have dealt with fundamental aspects, whereas in recent years, the technol- ogy of these devices has become the object of significant interest. This is mainly due to the fact that a probable application of DMFCs in portable power sources and in hybrid electrical vehicles has only recently been envisaged. The section on funda- mentals is particularly focused on the electrocatalysis of the methanol oxidation reaction and oxygen electroreduction. In this regard, particular relevance is given to the interpretation of the promoting effect on Pt of additional elements and some aspects of the electrocatalysis of oxygen reduction in the presence of methanol crossover have been treated. The technology section deals with the development of both components and devices. Particular emphasis is given to the development of high surface area electrocatalysts and alternative electrolyte membranes to Nafion, also the fabrication methodologies for the M&E assembly have been discussed. The last part of the paper describes the recent efforts in developing DMFC stacks for both portable and electro-traction applications. The current status of the technology in this field is presented and some important technical and economical challenges are been discussed. Keywords: Direct methanol fuel cells; methanol electrooxidation; fuel cell catalysts; polymer electrolyte membranes; M&E assembly, methanol cross-over, stacks, portable power sources, electrotraction. FUEL CELLS 2001, 1, No. 2 133 1615-6846/01/0207-133 $ 17.50+.50/0 REVIEW