Core@Shell Catalyst for PEMFC Application: New Approach Towards Non-Noble Metal Based Catalysis (2014)

With the rapid depletion of fossil fuels and increased environmental pollution due to vast fossil-fuel consumption, there is a need to explore clean and renewable energy sources that can substitute fossil fuels to enable sustainable energy development in our society. Renewable energy sources, such as solar, wind, geothermal and hydropower offer enormous potential for meeting future energy demands. Fuel cell technology has gained increasing attention as it provides promising and sustainable approach for the production of continuous power with reduced greenhouse gas emissions and higher efficiencies compared to combustion based technologies. In particular, proton exchange membrane fuel cells (PEMFCs) are considered to be suitable power sources for automobiles, consumer electronic devices and auxiliary power units due to advantages like use of hydrogen as fuel which is light-weight, clean and has a low operating temperature. This offers quick start-up, extended durability of system components, high power density with low weight and volume due to elimination of additional steps of fuel reformation. The simple system design would be reflected as an ease in operation, reduced cost and high reliability. Capital cost of the system is the major constraint limiting commercialization of PEMFCs due to use of expensive Pt/C catalyst. Hence, development of non-noble metal based catalysts with high electrochemical activity and durability is of interest to replace Pt. However, non-noble metals, cobalt and nickel have poor stability in acidic media. Stability of these metals can be improved by alloying or coating with catalytically active metals having high stability in acidic media. Following the latter approach, in this work, cobalt nanoparticles are coated with metal (M) which has shown promising performance as an anode catalyst for PEMFC application. In the present work, Co@M is explored as catalyst for PEMFC anode. Design of novel Co x @M 1-x (x = 0.6, 0.7, 0.8, 0.9) has been synthesized. Fig. 1 shows SEM micrograph of Co 0.7 @M 0.3 . Electrochemical characterization has been carried out in H 2 stream using 1N sulfuric acid (H 2 SO 4 ) as an electrolyte, Pt wire as counter electrode and Hg/Hg 2 SO 4 as reference electrode (+0.658V with respect to SHE). Results of the synthesis, microstructure, electrochemical activity and accelerated life test of these catalysts will be presented and discussed. References: Liu, C., et al., Advanced Materials for Energy Storage. Advanced Materials, 2010. 22 (8): p. E28-E62. Miller, J.R., Valuing Reversible Energy Storage. Science, 2012. 335 (6074): p. 1312-1313. Peng, B. and J. Chen, Functional materials with high-efficiency energy storage and conversion for batteries and fuel cells. Coordination Chemistry Reviews, 2009. 253 (23–24): p. 2805-2813. Whittingham, M.S., Materials challenges facing electrical energy storage. MRS Bull., 2008. 33 (4): p. 411-419. Tasic, G.S., et al., Non-noble metal catalyst for a future Pt free PEMFC. Electrochemistry Communications, 2009. 11 (11): p. 2097-2100. Oezaslan, M., F. Hasché, and P. Strasser, Pt-Based Core–Shell Catalyst Architectures for Oxygen Fuel Cell Electrodes. The Journal of Physical Chemistry Letters, 2013. 4 (19): p. 3273-3291. Acknowledgements: Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0001531. PNK also acknowledges the Edward R. Weidlein Chair Professorship funds, NSF and the Center for Complex Engineered Multifunctional Materials (CCEMM) for partial support of this research.