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

CBET-0756255固体氧化物燃料电池(SOFC)是将可燃燃料的化学能转化为电能的装置。固体氧化物燃料电池(SOFC)的重要组成部分是激活电化学催化反应的电极(阳极和阴极)。尽管SOFC是非常有前途的器件，但令人惊讶的是，人们对控制SOFC电极性能的电化学反应的基本机制知之甚少。例如，即使对于概念上非常简单的SOFC阳极上的氢氧化反应(H2 O2-=H2O 2E-)，也存在大量相互冲突的基本步骤机制，这些机制是基于各种实验提出的。最近该领域的综述论文以及各科学咨询委员会的报告都强调需要更好地在分子水平上了解固体电极和固体电解质界面上的电化学反应。本项目将使用量子密度泛函理论(DFT)计算来研究固体氧化物燃料电池(SOFC)阳极上电催化氧化反应的基本步骤机理。我们将使用真实的模型系统来解释金属/电解液界面的存在。在我们的第一性原理计算中，将考虑电位偏置和电场效应。虽然我们关注的是SOFC阳极，但所提出的方法是通用的，它可以很容易地用于解决其他固态电化学起作用的电催化系统，如固态传感器、微电子设备、固态电池等。我们注意到，本提案中概述的方法学以前没有被用于研究固态电化学。中心目标是帮助开发旨在发现新型SOFC材料的预测分子理论。为了实现这些目标，我们确定了四个主要目标：(1)我们将开发一种非常通用的方法，使我们能够从第一性原理研究多相电催化反应；(2)我们将评估基于先前的SOFC阳极实验研究提出的多种基本步骤机制的热力学可行性；(3)我们将通过将基本步骤信息整合到微观动力学模型中来研究各种建议机制的动力学，(4)我们将通过多项外展活动和一门新课程的开发，将该方法整合到我们的教育活动中。由于固态电化学反应很难进行实验探索，因此重点放在理论研究上。困难来自：(I)具有催化作用的重要金属/电解液界面位置的固有实验不可达性，(Ii)高电场，(Iii)高电位偏置，以及(Iii)发生这些反应的高温。拟议的理论框架将解决这些问题。我们已经进行了大量的前期工作，证明了建议方法的有效性。我们的中心教育目标是促进与能源相关的科学技术的分子方法。将通过多项外联活动和将教材纳入课程来实现教育目标。例如，我们小组将参加底特律地区大学预科工程计划(DAPCEP)，该计划为底特律地区7年级和8年级的学生提供免费的工程学课程，以及NASA暑期高中欣赏计划(SHARP)，旨在向高中生(10年级和11年级)介绍积极的科学研究。该研究项目中提出的概念也将通过引入一系列与能源和可持续发展有关的课程来整合到课程中。这将由系里的一些教员来教授，其中包括PI。此外，直接参与研究项目的研究生将接触到一套全面的理论和实验工具，这些工具将使他们能够解决大多数相关的电催化问题。此外，我们将设计一个教育模块，每年向夏季访问密歇根大学的大批高中生展示。在我们的实验室里，我们还为一名有前途的高中生提供了为期三个月的研究实习。

CBET-0756255LinicSolid 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 HighSchool 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.