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

CBET-0755253约翰逊这个项目是对硼氢化钠与水的水解反应机理的基础研究。这个反应最简单的形式是NaBH4+H2O=2H2+NaBO2。实际上，NaBH4水解法是燃料电池储氢的一种选择。由于NaBH4表面吸湿的复杂性以及水的吸附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开发历史，但这些步骤的基本机制在分子基础上还不清楚。特别是，南卡罗来纳大学最近的实验表明，当反应通过接触水蒸气和氢化物进行时，可以获得定量的氢产率。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，即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薄液层时，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一假说。具体目标是(1)量化允许发生水吸附和水解反应的反应包络(温度、压力和水蒸气组成的空间)；(2)在反应过程中获得实时、原位的拉曼光谱，以深入了解与吸附和反应相关的分子事件；以及(3)通过对NaBH4表面和水蒸气与表面的吸附和初始反应的分子模拟来理解和解释实验结果。这是一个合作的目标项目，合作伙伴包括南卡罗来纳大学、匹兹堡大学和新泽西州伊顿敦的千禧细胞公司。实验研究将在南卡罗来纳州进行，而分子模拟将在皮特大学进行。Millennium Cell，Inc.是一家制造基于NaBH4的氢气存储和发电系统的小企业。该项目继续了与南卡罗来纳州现有的智力合作，并将其扩展到匹兹堡大学。智力价值：这个项目代表了在分子水平上理解这种特殊的水解反应的尝试，这是一种更大类别的可能的水解反应之一。PIs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理有新的科学见解。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用第一性原理方法模拟。实时拉曼光谱将提供对反应的洞察，进而为分子模拟提供信息。更广泛的影响：对这一反应的研究对开发实用的氢存储系统具有直接影响。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。除了定期交流和传播研究成果外，合作伙伴还将定期进行实地考察。千禧细胞公司将每年招待一名研究生进行工业实习，以加强该项目的科学和工业信息流。这个基础科学项目是从位于南卡罗来纳大学的NSF资助的燃料电池工业/大学合作研究中心创造的环境中开发出来的。

CBET-0755253Johnson This 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.