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，电极表面的催化反应机制将使用安德森实验室开发的研究电化学界面的新理论进行预测和分析。在二维版本的新能带理论程序中，通过在电极上添加电荷和在双层中添加反电荷来调节表面电位。在介质连续介质模型中，采用改进的泊松-玻尔兹曼理论对双层电荷分布进行了建模。整个界面系统变化到电荷自一致性，得到了吉布斯自由能作为结构和电极电位的函数的预测。该理论已经被发现用于预测形成吸附在电极表面的反应中间体作为电位函数的可逆电位，将扩展到表征电极表面电子转移反应中的过渡态结构和活化能。将来，有效的能量转换和能量储存将越来越多地依赖于充分利用化学反应的吉布斯能（以电功的形式），而越来越少地依赖于化学反应的焓（以热和压力体积功的形式）。无论是生物系统中的酶还是燃料电池中的催化电极，都需要催化才能直接从燃料中产生电能。在分子结构和反应机理的层面上发展对电催化的理解是至关重要的。利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。两个主要的推力是：(1)获得对迄今为止限制燃料电池中铂电催化剂效率和稳定性的因素的基本理解，(2)应用所获得的见解来提出尚未发现的新电催化剂，可能不包括铂。研究结果将对广泛的科学界有所帮助，并将加速用于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.