GOALI: Collaborative Research. Phase Behavior and Reactivity of a Strongly Hygroscopic System

本项目是对硼氢化钠与水水解反应机理的基础性研究。这个反应最简单的形式是NaBH4 + H2O = 2h2 + NaBO2。实际上，NaBH4水解是燃料电池储氢的一种选择。由于NaBH4吸湿表面的复杂性以及吸水对反应动力学的影响，该反应具有重要的科学意义。尽管有很长的研究和发展历史，但这些步骤的基本机制还没有在分子基础上被理解。特别是，南卡罗来纳大学最近的实验表明，当将水蒸气与氢化物接触进行反应时，可以获得氢的定量产率。与水溶液水解相关的动力学限制在气相反应途径中不存在。然而，反应产率对温度和气相组成非常敏感。这一证据导致了这样的假设：反应途径的第一步是将水蒸气吸附到表面；随后，只有当足够的水被吸附形成一层薄薄的液体层时，反应才会进行。这个项目的目标是通过发展对水解反应的基本的、分子水平的理解来探索这个假设。具体目标是(1)量化反应包络层（温度、压力和水蒸气组成的空间），使水吸附和水解反应发生；(2)获取反应过程中的实时、原位拉曼光谱，深入了解与吸附和反应相关的分子事件；(3)通过分子模拟NaBH4表面以及水蒸气与表面的吸附和初始反应来理解和解释实验结果。这是一个由南卡罗来纳大学、匹兹堡大学和新泽西州伊顿镇的千禧细胞公司合作的GOALI项目。实验研究将在南卡罗莱纳进行，而分子模拟将在皮特进行。千禧电池公司是一家小型企业，生产基于NaBH4的储氢和发电系统。该项目延续了与南卡罗莱纳州现有的智力合作，并将其扩展到匹兹堡大学。智力优势：这个项目代表了在分子水平上理解这种特殊水解反应的尝试，这是一大类可能的水解反应之一。pi期望对高吸湿性氢化物表面的结构和反应性，以及吸附和反应机制有新的科学见解。从实验和理论上讲，这是一个具有挑战性的系统，因为在水吸附之后几乎同时发生反应。吸附现象的实验数据将采用第一性原理方法进行建模。实时拉曼光谱将提供对反应的深入了解，进而为分子模拟提供信息。更广泛的影响：该反应的研究对实际储氢系统的发展具有直接意义。GOALI计划将通过让工业科学家和工程师参与进来，加强这两个领先实验室的互动。除了定期通信和传播研究成果外，合作伙伴还将定期进行实地考察。千禧细胞公司将每年接待一名研究生进行工业实习，加强该项目的科学和工业信息流动。这个基础科学项目是由位于南卡罗来纳大学的nsf资助的工业/大学燃料电池合作研究中心所创造的环境发展起来的。

Matthews 0756089This project is a fundamental study of the mechanisms involved in the hydrolysis reaction of sodium borohydride with water. In its simplest form the reaction is written as NaBH4 + H2O = 2 H2 + NaBO2. Practically, NaBH4 hydrolysis is an option for hydrogen storage for fuel cells. The reaction is significant scientifically because of the complexity of the hygroscopic NaBH4 surface and the role of water sorption on the reaction kinetics. Despite a long history of research and development, the basic mechanism of these steps is not understood on a molecular basis. In particular, recent experiments at the University of South Carolina show that quantitative yields of hydrogen are obtained when the reaction is conducted by contacting water vapor with the hydride. The kinetic limitations associated with aqueous solution hydrolysis are not present in the gas phase reaction pathway. However, the reaction yields are very sensitive to temperature and gas phase composition. This evidence leads to the hypothesis that the first step in the reaction pathway is sorption of water vapor onto the surface; subsequently the reaction proceeds only when sufficient water has adsorbed to form a thin liquid layer. The goal of this project is to explore this hypothesis by developing a fundamental, molecular level understanding of the hydrolysis reaction. The specific objectives are (1) to quantify the reaction envelope (space of temperature, pressure, and composition of water vapor) that allows water sorption and the hydrolysis reaction to occur; (2) to obtain real-time, in situ Raman spectra during the course of the reaction to shed insight on the molecular events associated with adsorption and reaction, and (3) to understand and interpret experimental results through molecular simulation of the NaBH4 surface and the adsorption and initial reaction of water vapor with the surface.This is a collaborative, GOALI project that partners the University of South Carolina, the University of Pittsburgh, and Millennium Cell Inc. of Eatontown, NJ. Experimental studies will be conducted at South Carolina, while molecular simulations will be done at Pitt. Millennium Cell, Inc. is a small business that manufactures hydrogen storage and generation systems based on NaBH4. This project continues an existing intellectual collaboration with South Carolina, and extends it to the University of Pittsburgh. Intellectual Merit: This project represents an attempt at molecular level understanding of this particular hydrolysis reaction, which is one of a larger class of possible hydrolysis reactions. The PIs expect new scientific insights into the structure and reactivity of the highly hygroscopic hydride surface, and of the mechanisms of adsorption and reaction. Experimentally and theoretically this is a challenging system because of the near simultaneous reaction that follows water adsorption. Experimental data on the adsorption phenomenon will be modeled using first principles methods. The real-time Raman spectra will provide insight into the reaction that in turn will inform the molecular simulations. Broader Impacts: Study of this reaction has immediate implications for development of practical hydrogen storage systems. The GOALI program will enhance interaction of these two leading laboratories by involving industrial scientists and engineers. In addition to regular communications and dissemination of research results, the partners will engage in periodic site visits. Millennium Cell Inc. will annually host a graduate student on an industrial internship, strengthening the flow of scientific and industrial information for the project. This basic science project has been developed from the environment created by the NSF-funded Industry/University Cooperative Research Center for Fuel Cells, located at the University of South Carolina.