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 (001)-Ni oxide terminated surface being the most active. This is demonstrated through the effect on the energetics associated with surface oxygen exchange -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 to the traditional catalysts, while maintaining stability under reaction conditions. The findings reported here pave the way for engineering complex metal oxides with optimal activity.

Optimizing cathode materials for intermediate-temperature solid oxide fuel cells (SOFCs): Oxygen reduction on nanostructured lanthanum nickelate oxides

“…All chemicals are used as commercially received without further purification. The nanostructured LNO catalyst is prepared using a reverse-microemulsion assisted sol-gel method, as previously reported [10,11]. Two systems are separately prepared, each one containing a reverse-microemulsion consisting of cetyltrimethylammonium bromide (CTAB)/water/hexane/n-Butanol.…”

“…It has been reported that lanthanum nickelates (La 2 NiO 4+δ , LNO) exhibit higher electrochemical ORR activity and improved thermal compatibility with commonly used electrolytes when compared to most traditional perovskite oxides [9]. Furthermore, through a combined theoretical/experimental study, it has been established that the surface structure, controlled by the nanostructure, of lanthanum nickelates plays an important role in their catalytic activity [10,11]. 4 Control over the nanostructure of nickelate oxides can be very challenging when they are incorporated in SOFCs using current state-of-the-art fabrication methods, since these methods involve co-sintering of the electrode electrocatalyst with the electrolyte oxide (i.e., YSZ) at high temperatures (above 1000ºC), leading to chemical instability of the electrocatalyst and formation of undesired oxide phases that act as insulators at the electrode/electrolyte interface [7,19,20].…”

Comparison of Different Perovskite Cathodes in Solid Oxide Fuel Cells

“…Solid oxide fuel cells (SOFCs) have the advantages of high energy conversion efficiency and high electrode performance without a Pt catalyst among various types of fuel cells . However, SOFCs generally operate at 500–1,000 °C, resulting in severe performance degradation and increased cost over time .…”

The interaction of molecular oxygen on LaO terminated surfaces of La2NiO4

“…[17][18][19][20][21] The discovery represents a significant challenge for computational science which has to elucidate the chemical mechanisms that take place on that particular surface termination. 22,23 In addition, theoretical investigations suggest that relative stabilities of surfaces of perovskite related oxides are energetically equivalent for both terminations. 24,25 In an earlier investigation employing first principle techniques, the interaction of an oxygen molecule with La2NiO4 surfaces was reported by Zhou et al 26 In their work, the mechanisms of Recently, we used the DFT approach to investigate the oxygen reduction reaction on the SrOterminated surfaces of SrTiO3 and SrTi0.75Fe0.25O3-δ.…”