Array membrane electrode assemblies for high throughput screening of direct methanol fuel cell anode catalysts Renxuan Liu a , Eugene S. Smotkin a,b, * a NuVant Systems, 10 West 33rd Street, Suite 127, Chicago, IL 60616, USA b Department of Chemistry, University of Puerto Rico at Rio Piedras, San Juan, PR 00931, USA Received 6 February 2002; received in revised form 15 July 2002; accepted 13 August 2002 Abstract A fuel cell using an array membrane electrode assembly has been developed for the high throughput screening of fuel cell electrocatalysts. Standard membrane and electrode assembly methods are used. The use of modified fuel cell hardware permits the use of realistic catalyst exposure histories and steady state reaction conditions. The array fuel cell requires no supplemental electrolytes. The performance of the array fuel cell is demonstrated by the testing of one prepared in-house and three commercially available fuel cell catalysts. Within the potential range of a DMFC anode (i.e. 0.3  /0.4 V), the catalyst rankings were PtRu (Johnson Matthey) /PtRu oxide (E-Tek) /PtRu (reduced by NaBH 4 ) /Pt. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Array fuel cell; Membrane electrode assemblies 1. Introduction Direct methanol fuel cells (DMFCs) convert the chemical energy of methanol to electrical power by direct oxidation of methanol at a fuel cell anode. The poor anode and cathode kinetics of methanol/air electrochemistry precludes commercialization of DMFCs. Over 30 years ago PtRu was found to be the best, yet inadequate, catalyst for DMFCs [1  /5]. The anodic reaction of adsorbed CO with H 2 O is rate limiting at DMFC anodes. Thus catalysts that activate H 2 O at more negative potentials are needed. Other issues include catalyst ripening and degradation of catalyst j electrolyte and catalyst j support (typically carbon) interfaces. The search for better catalysts has motivated the development of high throughput screen- ing methods [6 /10]. Reports of combinatorial methods applied to electro- catalysis typically include catalyst array preparative methods tailored and linked to a novel high throughput screening method. The tight connection between the array preparative method and the screening method can lead to artifacts in the discovery of new catalysts. Array preparative methods include electrodeposition [7,8], sputter deposition [11,12], and deposition of metal ion precursors followed by borohydride reduction [9]. These preparative methods are not methods typically used for fuel cell catalyst preparation, although bulk catalysts have been augmented by sputter deposition of Pt on the catalytic surface [13]. The need for high metal dispersion in mixed metal DMFC catalysts limits preparation of bulk mixed metal catalysts to low temperatures. Thus phase segregation is prevalent and the number of phases, how the component metals distribute amongst those phases and the role of each phase in catalysis is directly linked to the preparative method. Typically, when catalyst arrays are prepared using metal salt precursors, a single reduction method is used across the array [9]. The use of a single reduction method across a library of elements with extreme nominal composition variations, combined with un-optimized well-less chemistry can result in varying degrees of incorporation of the metal ion components across the array. Thus no a priori knowledge of the relationship between nominal and actual compositions is possible. Examples exist where the ‘best catalyst’ identified in an array was an artifact of the preparative method. A * Corresponding author E-mail address: esmotkin@goliath.cnnet.clu.edu (E.S. Smotkin). Journal of Electroanalytical Chemistry 535 (2002) 49  /55 www.elsevier.com/locate/jelechem 0022-0728/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0022-0728(02)01144-0