UNS:Modeling Bulk Composition Dependent Alloy Surface Properties Under Reaction Conditions

Kitchin，1506770合金催化剂由两种或两种以上金属的混合物组成，在商业应用中被广泛使用，以比单一金属更有效地促进反应。然而，在设计新的催化剂时，很难预测两种或两种以上金属的哪种组合对给定的反应是最有效的，特别是因为气固催化反应中的活性表面中心通常在结构和组成上与主体合金不同。这项工作将开发一种改进的模型，用于预测合金催化剂在实际工作条件下的催化活性，从而能够发现新的和改进的合金催化剂，而不需要昂贵且耗时的合成和大量潜在金属组合的测试。这项工作解决了阻碍大块合金成分与催化反应活性直接相关的两个主要因素：表面偏析和吸附引起的表面成分变化。具体地说，研究的新方面是将表面位置分布函数(其中每个位置的反应性由密度泛函理论计算)与表面偏析模型(包括吸附诱导效应)相结合，以产生合金表面的统计加权平均性质。这种新的方法将被应用于优化的银钯合金的设计，用于乙炔在乙烯存在下的选择加氢-这是一种商业上重要的反应。本研究中开发的理论方法将对催化行业产生广泛的影响，使催化剂的设计比简单的试错法更有效，并通过生产比目前使用的催化剂更具活性、选择性和能效的催化剂。此外，研究人员将把他们的方法公开提供给催化社区，作为研究工具和教育工具。

Kitchin, 1506770Alloy catalysts, consisting of mixtures of two or more metals, are widely used in commercial applications to promote reactions more effectively than possible with a single metal. However, in designing new catalysts, it is difficult to predict which combinations of two or more metals will be the most effective for a given reaction, especially because the active surface sites in gas-solid catalytic reactions typically are different in structure and composition than those of the bulk alloy. This work will develop an improved model for predicting the catalytic reactivity of alloy catalysts under actual working conditions, thereby enabling the discovery of new and improved alloy catalysts without the need for costly and time-consuming synthesis and testing of large arrays of potential metal combinations. The work addresses two major factors that hinder direct correlation of bulk alloy composition with catalytic reactivity: surface segregation and adsorbate-induced changes in surface composition. Specifically, the novel aspect of the study is to combine a surface site distribution function (where the reactivity of each site is calculated by density functional theory) with a surface segregation model (that includes adsorbate-induced effects) to produce a statistically weighted average property of the alloy surface. The new approach will be applied to the design of optimized Ag-Pd alloys for the selective hydrogenation of acetylene in the presence of ethylene - a commercially important reaction. The theoretical methods developed in this study will have broad impact to the catalysis industry by enabling more efficient design of catalysts than simple trial-and-error methods, and by producing catalysts that are more active, selective, and energy-efficient than catalysts currently in use. In addition, the researchers will make their methods openly available to the catalysis community, both as a research tool and as an educational tool.