First-principles studies of heterogeneous electrochemistry: Electrochemical oxidation reactions over solid oxide fuel cell (SOFC) metal/electrolyte anodes

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

CBET-0756255 Linic Solid oxide fuel cells (SOFCs) are devices that convert chemical energy of combustible fuels into electricity. Important components of solid oxide fuel cells (SOFC) are electrodes (anode and cathode) which activate electrochemical catalytic reactions. Even though, SOFCs are very promising devices, it is astonishing how little is known about the underlying mechanisms of electrochemical reactions that govern the performance of the SOFC electrodes. For example, even for a conceptually very simple H2-oxidation reaction (H2 + O2- = H2O + 2e-) at the SOFC anode, there exist a large number of mutually conflicting elementary step mechanisms that have been proposed based on various experiments. Recent review papers in the field as well as the reports of various scientific advisory committees have emphasized the need for a better molecular level understanding of electrochemical reactions at interfaces of solid electrodes and solid electrolytes. This project will employ quantum Density Functional Theory (DFT) calculations to study elementary step mechanisms of electro-catalytic oxidation reactions over solid oxide fuel cell (SOFC) anodes. We will employ realistic model systems that account for the presence of the metal/electrolyte interface. Potential bias and electric field effects will be incorporated in our first principles calculations. While we focus on SOFC anodes, the proposed methodology is universal and it can be easily employed to address other electro-catalytic systems where solid-state electrochemistry plays a role, such as solid-state sensors, microelectronic devices, solid-state batteries, and many others. We note that the methodology outlined in this proposal has not been utilized previously to study solid-state electrochemistry. The central objective is to aid the development of predictive molecular theories aimed towards the discovery of novel SOFC material. To accomplish these objectives, we have identified four major goals: (1) we will develop a very general methodology that will allow us to study heterogeneous electro-catalytic reaction from first principles, (2) we will asses the thermodynamic feasibility of multiple elementary step mechanisms that have been proposed based on the previous experimental studies of SOFC anodes, (3) we will investigate the kinetics of the various proposed mechanisms by integrating the elementary step information into micro-kinetic models, (4) we will integrate the approach in our educational activities via multiple outreach activities and a new course development. The focus is on the theoretical studies since the solid-state electrochemical reactions are difficult to probe experimentally. The difficulties stem from: (i) an inherent experimental inaccessibility of the catalytically important metal/electrolyte interface sites, (ii) high electric fields, (iii) high potential bias, and (iii) high temperatures at which these reactions take place. The proposed theoretical framework will address these issues. We have already performed significant preliminary work demonstrating the usefulness of the proposed approach. Our central educational objective is to promote molecular approach to energy related science and technology. The educational objectives will be addressed via multiple outreach activities and the integration of the material into the curriculum. For example our group will participate in the Detroit Area Pre-College Engineering Program (DAPCEP) which offers free engineering classes to students in grades 7 and 8 from the Detroit area and the NASA Summer High School Appreciation Program (SHARP) which aims to introduce high school students (grade 10 and 11) to active scientific research. The concepts proposed in this research project will also be integrated into the curriculum by introducing a cluster of courses related to energy and sustainability. This will be taught by a number of faculty members, including the PI, in the department. Furthermore, graduate students who are directly involved in the research program will be exposed to a comprehensive set of theoretical and experimental tools that will allow them to tackle most of the relevant electro-catalysis issues. In addition, we will design an educational module that will be annually presented to large groups of high school students that visit the U of Michigan during summer months. In our laboratory, we also have a three months long research internship that we offer to a promising high school student.