The rapid depletion of fossil fuels and increased environmental pollution due to colossal consumption of ubiquitous fossil-fuel is a major impetus for efficient use of energy and exploration of renewable and clean energy sources.1, 2 Generation of electricity from renewable energy sources, such as solar, wind without producing carbon dioxide-an undesirable green house pollutant, offers enormous potential for meeting the future energy demands.3 Development of novel and efficient technology to store electrical energy is thus extremely important for meeting the global energy demand and environmental concerns. Fuel cell technology has garnered increasing attention over the years as it provides promising and sustainable approach for the production of continuous power with potential for reduced greenhouse gas emissions and higher efficiencies compared to hitherto 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 the advantages of using hydrogen as fuel which is light-weight, clean and has a low operating temperature. Hydrogen also offers quick start-up, extended durability of system components, high power density with low weight and volume due to elimination of additional steps needed for fuel reformation. The simple system design would be reflected as an ease in operation, reduced cost and high reliability. However, capital cost of the system is a major constraint limiting commercialization of PEMFCs due to use of expensive noble metal based Pt/C catalyst. Hence, development of non-noble metal based catalysts with high electrochemical activity and durability is of specific interest to replace Pt/C and thus, lower the cost of PEMFC system.
The present study explores Co1-x(Irx) (x=0.2, 0.3, 0.4) solid solution alloys as anode electro-catalyst for hydrogen oxidation reaction (HOR) for PEMFC applications. Fig. 1 shows the SEM micrograph of Co0.7(Ir0.3) with x-ray mapping of Co and Ir. The x-ray mapping shows homogeneous distribution of Co and Ir without segregation on any specific site. Electrochemical characterization has been carried out in H2 saturated 0.5 M sulfuric acid (H2SO4) as an electrolyte, employing Pt wire as the counter electrode and Hg/Hg2SO4 as the reference electrode (+0.65 V with respect to normal hydrogen electrode, NHE), using a scan rate of 10 mV/sec at a temperature of 40oC. The solid solution electro-catalyst Co1-x(Irx) (x=0.3, 0.4) exhibit superior electrochemical activity than Pt/C with electrochemical stability matching to that of Pt/C. In addition, to obtain a better understanding of the fundamental electrochemical activity of Co1-x(Irx) electro-catalyst, first-principles calculations of the total energies and electronic structures of the model systems with chemical compositions similar to those of the experimentally synthesized materials have been carried out to complement the present experimental study.
The electrochemical study conducted in half-cell configuration and single PEMFC full cell results shows the potential of Co1-x(Irx) (x=0.3, 0.4) as replacement of Pt/C, owing to the excellent electrochemical performance and stability. These results portend significant reduction in the overall capital cost of PEMFCs. The results of structural characterization and electrochemical activity of these electro-catalysts will be presented and discussed.
Research supported by the CBET, National Science Foundation, Grant-NSF-0933141. PNK also acknowledges the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) for partial support of this research.
See more of this Group/Topical: Topical Conference: Nanomaterials for Energy Applications