Collaborative Research: Understanding the Role of Surface Bound Ligands on Metals in H2O2 Direct Synthesis

合作研究：了解金属表面结合配体在 H2O2 直接合成中的作用

• 批准号: 2349884
• 负责人: Will Medlin
• 金额: $ 37.5万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-07-01 至 2027-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2349884&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Role; Surface

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Eranda Nikolla of the University of Michigan and Professor Will Medlin of the University of Colorado Boulder are studying new heterogeneous catalysts for the direct synthesis of hydrogen peroxide. Hydrogen peroxide is an important product for numerous applications including clean water and as an efficient oxidant in chemicals manufacturing. However, it is currently produced at industrial scale via an indirect process that involves reactions of organic chemicals and requires large scales to be economical. For distributed manufacturing, it is desirable to develop a “greener” process that directly reacts hydrogen with oxygen. However, new catalysts are needed to accelerate the rate of hydrogen peroxide synthesis and avoid side reactions that lead to complete hydrogen oxidation to water. Recent work has suggested that the application of certain organic coatings to common supported metal catalysts can improve hydrogen peroxide synthesis yields, however the way these improve performance is not understood. Professors Nikolla and Medlin and their teams will systematically vary the properties of the organic-metal interface to identify molecular features associated with high hydrogen peroxide yields. They will also conduct reaction kinetic studies to understand how interactions between the reactants and organic coatings specifically lead to enhanced rates. The research will be carried out by a multi-institutional team that includes collaboration with international and national laboratory partners. The educational component of the project will include training and exchange programs for graduate and undergraduate students and development of new online educational tools related to the research problem.Under this award, Professors Eranda Nikolla of the University of Michigan and Will Medlin of the University of Colorado Boulder are studying how the near-surface environment influences direct hydrogen peroxide synthesis on supported metal catalysts. Organic ligands are widely used in the synthesis of metal nanocrystals that can be employed as well-defined catalysts. While in many cases it is desirable to remove the ligands, in other instances the retention of ligands can lead to desirable catalyst performance. One important example in which ligand effects have been found to yield major selectivity improvements is the direct synthesis of hydrogen peroxide from H2 and O2 over Pd catalysts. While there have been some indications that the ligands function via (i) blocking of contiguous surface sites responsible for O2 activation and (ii) promotion of proton shuttling to adsorbed O2, the elementary-step mechanisms by which the coatings enhance selectivity in H2O2 direct synthesis are poorly understood. To develop structure-reactivity relations for hydrogen peroxide synthesis, Professors Nikolla and Medlin will systematically vary (a) the structure and density of ligands, (b) the metal nanoparticle size, shape, and composition, and (c) the solvent properties. The prepared materials will be characterized in depth and utilized in kinetic studies to understand the origins of selective catalysis. The project will involve collaborative efforts in nanoparticle synthesis, characterization of ligand-protected catalysts, reaction kinetic studies, and computational studies of chemistry at organic-modified metal surfaces. Although the project will emphasize the direct synthesis of hydrogen peroxide, the principles developed here can be extrapolated to diverse catalytic reactions, particularly since the elementary steps in direct synthesis and its undesired side reactions are broadly important in many chemistries.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.

在化学系化学催化项目的支持下，密歇根大学的 Eranda Nikolla 教授和科罗拉多大学博尔德分校的 Will Medlin 教授正在研究用于直接合成过氧化氢的新型多相催化剂。该产品具有多种用途，包括清洁水和化学品制造中的高效氧化剂。然而，目前它是通过涉及有机化学品反应的间接工艺进行工业规模生产的，并且需要大规模生产才能实现经济分配。在制造过程中，需要开发一种直接使氢气与氧气反应的“绿色”工艺，但是，需要新的催化剂来加速过氧化氢的合成速度并避免导致氢氧化物完全氧化成水的副反应。将某些有机涂层应用于常见的负载型金属催化剂可以提高过氧化氢的合成产率，但是尼古拉和梅德林教授及其团队将系统地改变有机金属界面的性质来识别分子，但这些提高性能的方式尚不清楚。相关功能他们还将进行反应动力学研究，以了解反应物和有机涂层之间的相互作用如何具体导致提高的速率。该研究将由一个多机构团队进行，其中包括与国际和国家实验室合作伙伴的合作。该项目的教育部分将包括针对研究生和本科生的培训和交流计划，以及开发与研究问题相关的新在线教育工具。密歇根大学的埃兰达·尼古拉（Eranda Nikolla）教授和密歇根大学的威尔·梅德林（Will Medlin）教授获得了该奖项。科罗拉多州博尔德正在学习近表面环境如何影响负载型金属催化剂上的过氧化氢直接合成，有机配体广泛用于可用作明确催化剂的金属纳米晶体的合成，但在许多情况下需要除去配体。在其他情况下，配体的保留可以带来理想的催化剂性能，其中一个重要的例子是通过 Pd 催化剂从 H2 和 O2 直接合成过氧化氢。配体通过（i）阻断负责 O2 活化的连续表面位点和（ii）促进质子穿梭至吸附的 O2 发挥作用，但涂层增强 H2O2 直接合成选择性的基本步骤机制尚不清楚。 -过氧化氢合成的反应性关系，Nikolla 和 Medlin 教授将系统地改变 (a) 配体的结构和密度，(b) 金属纳米颗粒的尺寸、形状和组成，以及 (c) 溶剂所制备的材料将被深入表征并用于动力学研究，以了解选择性催化的起源。该项目将涉及纳米粒子合成、配体保护催化剂的表征、反应动力学研究和化学计算研究方面的合作。尽管该项目将强调过氧化氢的直接合成，但这里开发的原理可以推断到各种催化反应，特别是因为直接合成的基本步骤及其不需要的副反应在许多反应中广泛重要。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。