High-Throughput Optical Screening of Electrocatalysts for Fuel Cell Applications – Review and Present Developments

Abstract

Abstract In this paper on high-throughput optical screening for the discovery and optimization of electrocalatysts for potential application in polymer electrolyte membrane and direct methanol fuel cells the present state-of-the-art in literature is reviewed focussing on non-optical and optical fast serial, semi-parallel or truly parallel screening techniques as well as actual improvements of the fluorescence based testing method to a semi-quantitative or even quantitative method are described. The modifications of the method are concerning hindrance of fluorescing colorant interdiffusion, optimization of system parameters concerning colorant, electrolyte and other measurement components, and application of correction procedures. With fluorescence based setups especially adapted to both anodic and cathodic half-cell reactions methanol oxidation as well as oxygen reduction reaction electrocatalysts have been screened. By iteratively passing through high-throughput optimization workflows several hundreds of precious metal-free as well as Pt containing compositions were synthesized, tested and validated by conventional cyclovoltammetric measurements. For electrocatalysts to oxidize methanol on the anodic side of the fuel cell a small amount of Pt seems to be indispensable to result in stable catalysts. For the oxygen reduction reaction active compositions performing comparable or even better than the reference PtOx catalyst contained the elements Co and Mn, which correspond to primary activity descriptors already specified in literature.