Conduction Mechanisms and Electrocatalysis in Emerging Double Perovskite Materials
Abstract
Conduction Mechanisms and Electrocatalytic Activity in Novel Double Perovskite Materials Objective. Research described in this proposal will examine the mechanisms responsible for unusually high conductivity observed in the double perovskite materials Sr2-xVMoO6-? (SVMO). Under reducing conditions, SVMO undergoes a reversible semi-conductor to metallic transition above 600?C, but the origin of this behavior is unclear. SVMOÕs metallic character persists upon cooling leading to unprecedentedly high conductivity for mixed ion electron conducting (MIEC) materials at temperatures as low as 300?C. Upon exposure to air, SVMOÕs returns to having semi conductor behavior. The proposed research program will investigate the SVMOÕs conduction mechanisms and will be driven by three objectives: 1. Identify the origin of SVMOÕs Ômetal-likeÕ conductivities and determine how this property changes with processing conditions, temperature, material stoichiometry and ambient atmosphere. This goal will identify links between cation oxidation states, cation ratios, and oxygen stoichiometry and a previously observed semi-conducting to metallic transition. These studies will also determine the materialÕs transference number (ratio of electron conductivity to ion conductivity) and how it changes with conditions and stoichiometry. 2. Quantify SVMOÕs thermal and pO2 stability as a function of temperature, ambient atmosphere composition, stoichiometry and applied electrochemical polarization. 3. Explore SVMOÕs performance as an electrode in solid-oxide electrochemical cells operating in both fuel cell and electrolysis mode. These studies will also benchmark SVMOÕs performance against traditional metallic and cermet systems and characterize SVMOÕs susceptibility to carbon accumulation. Methods. To accomplish the objectives described above, research will require coordinated activity in several different areas. Experiments will utilize operando, in situ, and ex situ techniques. Operando measurements refer to experiments carried out under thermal, atmospheric and electrochemical conditions typically encountered in application environments and include electrochemical methods such as voltammetry and impedance spectroscopy as well as vibrational Raman scattering. In situ describes experiments performed where control over one (or more) operational condition is sacrificed in order to perform the measurement. Examples include temperature dependent 4-probe conductivity (under a single atmosphere and X-ray diffraction, where lattice structure is determined versus temperature but under high vacuum. Ex situ measurements such as scanning electron microscopy, XPS, and nano-Auger spectroscopy will be used for comparing differences in material structure and composition before and after testing. Significance (to the advancement of knowledge). MIEC ceramics are a class of emerging materials capable of transforming how chemical energy is converted into electrical power and vice versa. Specifically, MIEC ceramics have been proposed as materials that will enable the development of reversible solid-oxide electrochemical cells that can either drive the electrochemical oxidation of fuels to produce electricity and products (Òfuel cell modeÓ) or operate under a reverse bias, electrolyzing ÔproductsÕ such as COÂ2 or H2O to synthesize high value species including CO, CH3OH, and olefins (Òelectrolysis modeÓ). If successful, the proposed research will result in a roadmap capable of predicting and tailoring mixed ion electron (MIEC) properties, specifically those with several multi-valent cations, through carefully controlled stoichiometry and processing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 28, 2022
- Source ID
- W911NF2210283
Entities
People
- Robert A Walker
Organizations
- Army Contracting Command
- Montana State University
- United States Army