Engineering Complex, Layered Metal Oxides: High-Performance Nickelate Oxide Nanostructures for Oxygen Exchange and Reduction

Abstract

Synthetically tuning the surface properties of many oxide catalysts to optimize their catalytic activity has been appreciably challenging, given their complex crystal structure. Nickelate oxides (e.g., La2NiO4+δ) are among complex, layered oxides with great potential toward efficiently catalyzing chemical/electrochemical reactions involving oxygen (oxygen reduction, ammonia oxidation). Our theoretical calculations show that the surface structure of La2NiO4+δ plays a critical role in its activity, with the (001)-Ni oxide-terminated surface being the most active. This is demonstrated through the effect on the energetics associated with surface oxygen exchange, a key process in reactions involving oxygen on these oxides. Using a reverse microemulsion method, we have synthesized La2NiO4+δ nanorod-structured catalysts highly populated by (001)-Ni oxide-terminated surfaces. We show that these nanostructures exhibit superior catalytic activity toward oxygen exchange/reduction as compared with traditional catalysts while maintaining stability under reaction conditions. The findings reported here pave the way for engineering complex metal oxides with optimal activity.