A stable and cost-effective anode catalyst structure for formic acid fuel cells.

Abstract

The high energy density, fast oxidation kinetics, and convenience of use of liquid formic acid (HCOOH), as well as the simplicity of power-system integration make direct formic acid fuel cells (DFAFCs) a promising power source for portable device applications. Considerable progress in aspects of DFAFC research and engineering has been achieved in recent years, which has enabled the fuel-cell technology to be implemented in practical devices. However, large-scale practical commercialization has been limited by several challenging issues such as high anode overpotential, excessive fuel and water permeability of the polymer electrolyte membrane, and questionable long-term durability of the fuel cells. The issue of high overpotential for anode catalysts is associated with the formation of poisons on the catalyst surface and also with the large amount of catalyst loading. To date, despite the problem of being strongly poisoned by intermediate species, Pt is the best-known anode catalyst for the oxidation of small organic molecules. Besides Pt, Pd catalysts have recently shown superior performances compared to platinum-based catalysts in the oxidation ultrapure HCOOH in DFAFCs, because of the great initial activity of Pd, even at low temperature. However, Pd catalysts have a significant drawback; their high performance is not sustained for extended time periods, largely because of the vulnerability of these catalysts towards uncharacterized intermediate species and the potential for the dissolution of Pd in acidic solutions. To enhance the power performance as well as the durability of the catalyst, we have recently demonstrated that irreversible modification of the Pt metal surface with foreign metal adatoms such as Bi, Pb , and Sb is a powerful method to drive a practical DFAFC system. In addition, an effective anode structure that alleviates mass transport of HCOOH in the membrane electrode assembly (MEA) enabled us to reduce the amount of Pt loading and extend the range of the HCOOH concentration windows. Herein, we report a novel approach for the fabrication of more stable and cost-effective anode catalysts for DFAFC by using a three-step electrochemical process. The newly developed catalyst, which contains Pt modified with Bi, is directly applied to the fuel cell to evaluate its catalytic activity and performance. The PtBi catalyst was fabricated in three consecutive electrochemical steps, namely: 1) electrochemical oxidation of carbon paper to form the adequate catalyst support, followed by 2) Pt electrodeposition, and 3) underpotential deposition (UPD) of Bi onto the Pt. The conceptual design of the final electrode is illustrated schematically in Figure 1 and

DOI: 10.1002/anie.200803466

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Cite this paper

@article{Uhm2008ASA, title={A stable and cost-effective anode catalyst structure for formic acid fuel cells.}, author={Sunghyun Uhm and Hye Jin Lee and Youngkook Kwon and Jaeyoung Lee}, journal={Angewandte Chemie}, year={2008}, volume={47 52}, pages={10163-6} }