Oxygen Reduction and Evolution

About

Effective functioning of such devices as batteries and fuel cells relies upon the efficiency of the electrochemical reactions that occur at the cathodes/anodes of these devices, and such efficiency requires a good catalyst. For many reactions within fuel cells, including oxygen reduction reactions (ORR) and oxygen evolution reactions (OER), developments in the use of transition metal-oxide systems have been sought as an alternative to the customarily very expensive, established catalysts such as platinum/iridium oxide. Such catalysts have proven to be active for ORR/OER electrochemical reactions; however, those metal-oxide composite catalysts that have been developed thus far possess many drawbacks, including low stability in alkaline media, low activity compared to the conventional ORR/OER catalyst (platinum/iridium oxide), and low surface area. A method and formulation of catalysts that can overcome these drawbacks and yet still offer a low cost and thus, better commercial viability is sought. Researchers have developed a method of preparing transition metal-oxide catalysts for use in such devices as fuel cells, which relies on the use of sacrificial supports and can be accomplished with readily available/inexpensive nitrate precursor materials. These precursor materials are deposited onto the surface and into the pores of the sacrificial support. This is followed by a heat treatment and etching of the support, resulting in a product catalyst that, based on the nature and ratio of the materials used, as well as the heat treatment temperature profile and chemical environment, can exhibit optimal catalyst performance. Tests have shown that mixed-oxide catalysts prepared from copper and cobalt precursors using this innovative method possess high activity in alkaline and neutral media. Additionally, the use of the sacrificial support in the preparation of these catalysts allows for a more porous product and thus more potential active sites for ORR/OER to occur – increasing performance of the catalyst and thus, efficiency of the end device (i.e. fuel cells, batteries, etc.). These product catalysts can be deposited onto conductive dispersed supports that are either carbon or non-carbon in such a manner as to facilitate charge transfer.