Apparent Oxygen Uphill Diffusion in La_0.8Sr_0.2MnO₃ Thin Films upon Cathodic Polarization

Abstract

The impact of cathodic bias on oxygen transport in La0.8Sr0.2MnO3 (LSM) thin films was investigated. Columnar‐grown LSM thin films with different microstructures were deposited by pulsed laser deposition. 18O tracer experiments were performed on thin film microelectrodes with an applied cathodic bias of −300 or −450 mV, and the microelectrodes were subsequently analyzed by time‐of‐flight secondary ion mass spectrometry. The 18O concentration in the cathodically polarized LSM microelectrodes was strongly increased relative to that in the thermally annealed film (without bias). Most remarkable, however, was the appearance of a pronounced 18O fraction maximum in the center of the films. This strongly depended on the applied bias and on the microstructure of the LSM thin layers. The unusual shape of the 18O depth profiles was caused by a combination of Wagner–Hebb‐type stoichiometry polarization of the LSM bulk, fast grain boundary transport and voltage‐induced modification of the oxygen incorporation kinetics,

Experimental Design for Voltage Driven Tracer Incorporation and Diffusion Studies on Oxide Thin Film Electrodes

“…Similar apparent uphill diffusion profiles were already reported in our previous study on LSM microelectrodes. 19 They result from a combination of fast oxygen diffusion along grain boundaries and depth dependent bias activated "leakage" into the bulk, see the detailed discussion below. It should be emphasized that only the given electrode geometry with well-defined lateral variation of the overpotential enabled us to collect this large amount of information from a single tracer experiment.…”

“…z E-mail: j.fleig@tuwien.ac.at to surprising tracer profiles with apparent uphill diffusion at higher overpotentials. 19 However, given the nature of oxygen exchange experiments, in contrast to bias dependent impedance measurements, a systematic study of the bias dependent tracer incorporation requires many different samples, one for each bias voltage. In this contribution, we suggest a novel approach that markedly simplifies bias dependent tracer incorporation measurements.…”

(Invited) Towards an Improved Understanding of Electrochemical Oxygen Exchange Reactions on Mixed Conducting Oxides

“…The oxygen chemical potential change due to an overpotential can be described in terms of defects by [7] results from Eqs. 5 and 6, which means that the vacancy concentration drastically changes under polarization, as exemplified for LSM (10). This has a consequence at the MIEC/electrolyte interface: From Eqs.…”

Gold nanoparticle-based sensing platform of hydrazine, sulfite, and nitrite for food safety and environmental monitoring

“…The metal and semiconductor nanoparticles has gained enormous interest on the electrochemical interfaces to develop the electrochemical nanoscale systems for various catalytic and sensor applications (Alammari et al 2015;Keeley et al 2016;Wang et al 2016;Wang et al 2015). The metal nanoparticles play a key role in catalytic and electrocatalytic reactions which may empower numerous functionalities to line up for the targeted applications because of the interactivity of essential nanostructured sensor elements with their immediate local environments (Chen and Chatterjee 2013;Govindhan et al 2014, Huber et al 2015Maduraiveeran and Ramaraj 2009). Especially, gold nanoparticles (Au NPs) have found use in areas ranging from chemical separations and sensing to direct applications in the medical, food, and environmental community due to their unique chemical, optical, and electronic properties (Huber and Leopold 2016;Moghimi et al 2015;Wang et al 2015;Zhang et al 2017).…”