Comprehensive First Principles Approach to Understanding the Electrochemical Interface and Applications to Energy Problems

在这项由分析和表面化学计划支持的研究中，将使用安德森实验室开发的用于研究电化学界面的新理论来预测和分析电极表面的催化反应机理。在新的能带理论程序的二维版本中，通过在电极上添加电荷和在双层中添加反电荷来调整表面电势。在介电连续介质模型中，双层电荷分布用改进的泊松-玻尔兹曼理论来模拟。整个界面体系变化为电荷自洽，给出了吉布斯自由能随结构和电极电势的函数的预测。这一理论对于预测吸附在电极表面的反应中间体的可逆势是有用的，它将被推广到表征电极表面电子转移反应的过渡态结构和活化能。在未来，有效的能量转换和能量存储将越来越多地依赖于以电功的形式充分利用化学反应的吉布斯能量，而越来越少地依赖于以热和压力-体积功的形式的化学反应的热能。无论是生物系统中的酶还是燃料电池中的催化电极，直接从燃料中产生电功都需要催化作用。在分子结构和反应机理的水平上理解电催化是至关重要的。使用安德森实验室开发的理论实现这一目标的工作已经开始，该计划支持的研究将产生重大进展。两个主要的努力是：(I)对迄今为止限制燃料电池中铂电催化剂的效率和稳定性的因素有基本的了解；(Ii)将所获得的洞察力应用于提出新的电催化剂，可能不包括尚未发现的铂。研究结果将有助于广泛的科学界，并将加快交通运输和移动电子设备应用的高效便携式电源的开发。

In this research supported by the Analytical and Surface Chemistry Program, catalytic reaction mechanisms on electrode surfaces will be predicted and analyzed using a new theory developed in the Anderson lab for studying electrochemical interfaces. In the two-dimensional version of the new band theory program, the surface potential is adjusted by adding charge to the electrode and counter charge in the double layer. The double layer charge distribution is modeled by a modified Poisson-Boltzmann theory within a dielectric continuum model. The whole interfacial system is varied to charge self-consistency, yielding predictions of the Gibbs free energies as functions of structure and electrode potential. The theory, already found useful for predicting reversible potentials for forming reaction intermediates adsorbed on electrode surfaces as functions of potential, will be extended to characterizing transition state structures and activation energies during electron transfer reactions on electrode surfaces. Efficient energy conversion and energy storage will in the future depend more and more on making the best use of the Gibbs energy of chemical reactions in the form of electrical work and less and less on the enthalpy of chemical reactions in the form of heat and pressure-volume work. Catalysis is required to generate electrical work directly from fuels, whether by enzymes in biological systems or catalytic electrodes in fuel cells. It is critical to develop an understanding of electrocatalysis at the level of molecular structures and reaction mechanisms. Work toward this goal using the theory developed in the Anderson lab has begun and the research supported by the program will yield significant advancements. Two major thrusts are (i) gaining fundamental understanding of the factors that so far limit the efficiency and stability of platinum electrocatalysts in fuel cells, (ii) applying the insight gained to proposing new electrocatalysts, possibly not including platinum, that are as yet undiscovered. The results will be helpful to a broad scientific community and should speed the development of efficient portable electric power sources for transportation and mobile electronic device applications.