A Complexed Sol-Gel (CSG) Approach to High Surface Area (HSA) Durable Ultra Active Platinum-Ruthenium Electro-Catalysts for Direct Methanol Fuel Cells

Direct Methanol Fuel Cell (DMFC) is a promising power source for continuous generation of energy without evolution of any toxic by-products and greenhouse gases. Pt-Ru has been the accepted gold standard anode electro-catalyst for DMFC, but significant advances are required to enhance its performance and stability. A complexed sol-gel (CSG) approach has been used to develop nanostructured powder materials. Herein we report a novel CSG process to synthesize nanoparticulate high specific surface area (HSA), completely unsupported Pt(Ru) based electro-catalyst exhibiting three fold higher electrochemically active surface area (ECSA) and ultra high electrochemical performance compared to commercially available Johnson Matthey Pt-Ru black catalyst, the currently accepted gold standard. Furthermore, in identical single full cell DMFC configuration tests for methanol oxidation, current and power densities ∼40% higher than that displayed by Johnson Matthey catalyst is achieved. Proton exchange membrane fuel cells (PEMFCs) are ubiquitously known for efficient continuous energy and power generation with reduced greenhouse emissions. Commercialization of low cost PEMFCs have however been thwarted by inferior catalyst activity and stability hence limited by loading constraints. • C), has been considered for applications that require faster start-up times, and frequent starts and stops such as automotive applications, material handling equipment, and auxiliary backup power systems. 1-5 On the other hand, methanol-powered direct methanol fuel cell (DMFC) are well suited for portable power applications in consumer electronic devices wherein the power requirements are low. 3-7 A significant fraction of the cost of DMFC and PEMFC arises from the use of precious metal catalysts hitherto platinum group-metal (PGM) catalysts currently used to accelerate electrochemical reactions at the electrodes. 3-8 For widespread commercialization of PEMFC and DMFCs, there is a critical need for continued advancements to minimize PGM loading or the development of equally performing non-PGM catalysts alternatives to reduce the cost. 3-10 The durability of catalysts is also a major issue under conditions of load-cycling in harsh corrosive environment. Mitigation of catalyst dissolution/degradation during operation of low and high-temperature fuel cells will certainly translate alone to higher performance leading to reduce costs. 3-11 Moreover, while addressing cost and durability, fuel cell performance and efficiency must also meet or exceed that of competing technologies (e.g. battery) to allow for market penetration and the benefits of this technology. In light of the current situation, it is of paramount importance to design and synthesize effective electro-catalysts with improved electrochemical activity, improved durability/stability, and significantly reduced precious metal loading to ultra-low levels exhibiting enhanced tolerance to air, fuel and system-derived impurities. To meet these tremendous constraints on performance and efficiency, durability and * Electrochemical Society Student Member. * * Electrochemical Society Active Member. z E-mail: [email protected] cost requirements of fuel cells, significant research has been conducted over the years focusing largely on identifying new materials, and developing novel design and fabrication methods for catalysts and supports. 3-13 Carbon monoxide generated during methanol oxidation reaction (MOR) as it is the surface bound intermediate at low temperatures during DMFC operation further inevitably leads to poisoning of the platinum catalyst surface which reduces the catalytic activity of platinum thus causing it to become inactive if used by itself. In this context, a novel complexed sol-gel process (CSG) has been developed by our group to synthesize unsupported nanocrystalline PtRu based binary, ternary and quaternary solid solutions having high ESCA with excellent electrochemical activity and durable microstructure for the methanol oxidation reaction