Novel Ternary and Doped Transition Metal Oxide Oxygen Evolution Electro-Catalysts for Hydrogen Production Via PEM Based Water Electrolysis

Hallmark of a sustainable world is one wherein energy demands are consistently met with renewable energy sources. In this regards, hydrogen is often touted as the “magic” fuel of the future if it can be derived from renewable systems such as solar energy as the source of electrical potential required for splitting water by electrolysis. Hydrogen one of the most abundant and lightweight element in the universe is also a clean and efficient energy carrier in contrast to the fossil fuels which are continuously depleting by the day. Hydrogen is considered the “forever fuel” since it can be produced from any primary energy fuel. A hydrogen based energy system can thus be considered benign and very much desirable for delivering high quality energy services in an efficient, clean and safe manner contributing to achieving the sustainability goals. Hydrogen is mainly produced currently from fossil fuels via steam reforming or partial oxidation of natural gas, which generates large amounts of carbon dioxide in turn contributing to global warming and ozone depletion. Production of hydrogen by electrolysis of water is thus considered a potential, practical solution. Electrolysis is less efficient than the chemical pathway but offers virtually no pollution or toxic byproducts if the electric current is generated using renewable energy sources. Currently established technologies for producing hydrogen require significant improvements in their technical and economic performance (efficiency and costs) if hydrogen is to be produced for energy use. High capital costs are thus incurred due to use of expensive materials, relatively small systems, reasonably low efficiencies, customized power electronics, coupled with labor intensive fabrication.

For proton exchange membrane (PEM) electrolysis cells, use of non-precious metal catalysts for electrodes with high activity and durability would significantly decrease the overall capital costs. While intense research is being conducted for identifying a completely non-noble metal catalyst for PEM system, approaches to decrease noble metal loading is extremely critical. Decreasing the noble metal loading as well as improving the catalytic activity and durability could be achieved using novel synthesis techniques to generate high surface area nano electro-catalyst, or identifying approaches to generate low cost support structures (diluents) for electro-catalyst. The present work is thus carried out to identify a novel support for electro-catalyst which can appreciably decrease the precious metal loading without compromising the electrochemical activity and correspondingly improving the corrosion stability of noble metal oxide electro-catalyst.

Non-noble metal oxides though chemically stable are known to display however, no catalytic activity for oxygen reduction processes. Mixed oxides obtained by the addition of economically cheaper alternatives to noble metal oxides could offer significant cost effective options if the systems exhibited catalytic activity, chemical stability, and electronic conductivity similar to the currently accepted gold standard, IrO₂ electro-catalysts used in PEM based water electrolysis. On the grounds of the very promising performances shown by both IrO₂-SnO₂ and IrO₂-Nb₂O₅ mixtures as an anode electro-catalyst, the present investigation has been conducted to explore the synthesis and characterization of novel composite-ternary transition metal oxide systems. Also, in the present research pure and group VII doped SnO₂ solid solution with IrO₂ has been explored as electro-catalysts. Results to date indicate that compositions containing 80% reduction in noble metal oxide exhibit comparable electrochemical activity to pure IrO₂.