SYNTHESIS, CHARACTERIZATION AND RIETVELD ANALYSIS OF LNFEO3 (LN = LA TO LU)

ISMAEL O. FÁBREGAS; EUGENIO OTAL; KIM MANUELA

Congreso; XVI reunion de la asociación argentina de cristalografía; 2021

The shift to green and renewable energy production to diminish or negate climate change has stimulated ample research in the areas of energy conversion, storage and transmission. Nowadays, one of the tougher problems is the development of an efficient and cost-effective catalyst for oxygen reduction (ORR) and evolution (OER). The slow kinetic is the main problem. One of the most used catalysts, platinum@carbon, faces availability and costs problems if used in a massive scale.Orthoferrites are oxide-based catalysts that have received wide attention because they present lower but acceptable activity for ORR/OER [1], in particular the LnFeO3 series (Ln = lanthanide) is advantageously composed of materials of lower costs and higher abundance: iron is the 4th most abundant element on the earth crust and the rare earths, at least an order of magnitude more abundant than noble metals.The LnFeO3series, (Ln = La-Lu) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Rietveld analysis. LnFeO3 have a tetragonal space group independently of the Ln in A-site (i.e., here is no phase transition in the series). Rietveld analysis allowed the identification of a series of systematic changes in the Ln?s and O?s positions, cell volume and constants, tilt angle of the Glazer octahedra and Fe-O-Fe angle, as Ln change to Lu from La.All these changes allowed us to detect a change in polarity in some crystallographic planes, either an increase or a reduction, while other remained constant. We can correlate this change in polarity with the notable morphology change observed by SEM. Beyond this work we expect to correlate this changes with the kinetics of a ORR/OER electrode composed of LnFeO3, hoping to obtain a better understanding of its mechanism and thus design better catalysts without the use of precious metals in their composition.