Probing the Nature of the Single-Atom Sites in Single-Site Alloy (SAA) Catalysts

用于加速化学反应的固体催化剂在工业中非常常见，大约80%的化学过程使用固体催化剂。固体催化剂被应用于日益复杂的反应体系。催化剂选择和使用的主要挑战是需要更好地控制形成哪些产品(选择性)。在这个项目中，加州大学河滨分校的Francisco Zaera教授正在探索使用单原子合金(SAA)催化剂作为提高反应选择性的一种方法。这类新型催化剂是一种在重要的工业反应中实现高选择性和高活性的新途径。促进化合物选择性氢化的能力有望影响食品、化妆品、制药和精细化学品行业的工艺。一般而言，更具选择性的催化工艺会带来重要的好处，如降低原材料消耗、提高效率和最大限度地减少废物--所有这些都是对更环保工艺的要求。从Zaera的研究中获得的知识被用来在本科生和研究生课程中说明动力学、催化和材料合成的基本原理。扎埃拉教授正在与拉丁美洲的研究小组广泛合作。他鼓励学生参与研究中代表性不足的群体。在化学系化学催化项目的资助下，加州大学的Francisco Zaera教授正在对单原子合金(SAA)催化剂的功能有一个基本的了解，特别是使用CuPT双金属来促进不饱和碳氢化合物的选择性加氢。他的主要假设是，与目前最先进的研究表明的那样，作为孤立的单个原子，少数组分(铂)的单个原子可能会改变表面原子的电子性质。Zaera团队正在通过两种平行的实验方法来探索这一想法。他的团队使用高通量分子束来模拟催化所需的大气压条件，研究模型系统。该团队正在使用所谓的“高压室”，在催化过程中进行原位反射吸收红外光谱(IR)实验。Zaera教授还研究了催化条件下现实的负载型催化剂，进行了原位IR滴定，以识别和定量可能分离到表面的铂原子。用原位X射线吸收光谱(XAS)研究了铂原子周围配位球的变化以及铜原子的性质(氧化态)。Zaera教授强调招聘女性和少数族裔，包括STEM专业的访问国际学生和拉丁美洲学者。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Solid catalysts - used to speed up chemical reactions - are very common in industry and used in approximately 80% of all chemical processes. Solid catalysts are applied to increasingly complex reaction systems. The main challenge of catalyst selection and use is the need to better control which product or products are formed (selectivity). In this project, Professor Francisco Zaera of the University of California, Riverside is exploring the use of single-atom alloy (SAA) catalysts as a way to improve reaction selectivity. This new class of catalysts is a new and promising approach towards both high selectivity and high activity in important classes of industrially reactions. The ability to promote the selective hydrogenation of chemical compounds promises to impact processes in the food, cosmetics, pharmaceuticals, and fine chemicals industries. In general, more selective catalytic processes lead to important benefits such as lower raw material consumption, increased efficiency, and waste minimization - all requirements for more environmentally-friendly processes. The knowledge derived from Zaera's research is used to illustrate basic principles in kinetics, catalysis, and materials synthesis in undergraduate and graduate classes. Professor Zaera is collaborating extensively with Latin American research groups. He encourages student participation from groups underrepresented in research. With funding from the Chemical Catalysis Program of the Division of Chemistry, Professor Francisco Zaera of the University of California, Riverside is developing a fundamental understanding of how single-atom alloy (SAA) catalysts function, with special focus on the use of CuPt bimetallics to promote the selective hydrogenation of unsaturated hydrocarbons. His main hypothesis is that, rather than acting as isolated single atoms as the present state-of-the-art research suggests, the single atoms of the minority component (Pt) may alter the electronic properties of the surface atoms. The Zaera group is probing this idea by following two parallel experimental approaches. His group studies model systems using high-flux molecular beams to emulate the atmospheric pressure conditions needed for catalysis. The team is employing a so-called "high-pressure cell" to carry out in-situ reflection-absorption infrared spectroscopy (IR) experiments during catalysis. Professor Zaera also studies realistic supported catalysts under catalytic conditions, performing in situ IR titrations to identify and quantify the Pt atoms that may segregate to the surface. In-situ X-ray absorption (XAS) spectroscopy is used to evaluate any possible changes in the coordination sphere around the Pt atoms as well as the nature (oxidation state) of the Cu atoms. Professor Zaera emphasizes the recruitment of women and minorities including visiting international students and scholars from Latin America in STEM professions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.