High-Throughput Activity and Performance Screening Methods for PGM-Free Catalysts

Abstract

Platinum is widely used as the catalyst in polymer electrolyte fuel cells (PEFCs) due to its high catalytic activity and stability. However, the high cost of this precious metal is one of main barriers to widespread commercialization of PEFCs in automotive and stationary applications. Many research efforts have focused on reducing this cost barrier by either decreasing the platinum loading by developing more active Pt-based catalysts, such as nanostructured alloys, or by developing platinum group metal-free (PGM-free) catalysts based on earth-abundant materials, such as iron, cobalt, carbon, and nitrogen [1-4]. The overall approach of this project is to accelerate the development of PGM-free catalysts by developing high-throughput materials synthesis, characterization, and performance evaluation methodologies. A multi-channel flow double electrode (m-CFDE) cell, based on previous work by M. Watanabe’s group [5], has recently been designed and tested for the simultaneous screening of the catalytic activity of multiple samples in an aqueous environment [6]. An automated robotic catalyst ink dispensing system has been developed for precise deposition of nano-liter ink droplets across the m-CFDE glassy carbon electrodes (1 mm × 3 mm). The nano-liter injector with exchangeable micro-tips deposits the electrode ink onto the tiny surface glassy carbon at a precise injection speed. The removable electrode plugs of the m-CFDE cell are fixed on a numerically-controlled XY table to uniformly distribute the PGM-free catalyst across the glassy-carbon electrode. This automated deposition stage provides better reproducibility and uniform distribution over the conventional hand deposition using micropipettes as is typically utilized for ink deposition for rotating disk electrode measurements. In the performance evaluation aspect, a commercial combinatorial membrane-electrode assembly (MEA) test system has been further developed and utilized to simultaneously evaluate the fuel cell performance of 25 electrodes with different catalyst and ionomer-to-carbon ratios. The automated electrode deposition system in combination with a custom-designed heated vacuum table mounted on the XY table has also been used to make a catalyst-coated membrane (CCM) with 25 segmented electrodes. The results of application of this high-throughput methodology to a promising class of PGM-free catalysts will be discussed. Acknowledgements This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the auspices of the Electrocatalysis Consortium (ElectroCat). Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, under contract DE-AC-02-06CH11357.