CAREER: CAS: Colloidal Ligand-Exchange Synthesis of Dilute Noble Metal Surfaces for Electrosynthesis of Hydrogen Peroxide

在化学系化学催化项目的支持下，普渡大学的Christina W. Li教授正在研究催化剂，以有效地利用电力从空气和水直接制备过氧化氢。过氧化氢是一种重要的商品化学品，在水净化和消毒中有着广泛的应用。在开发高效催化剂方面，该项目有可能实现在基础设施薄弱地区部署的小规模流动生产。从空气和水中制造过氧化氢是目前氢基工艺的可持续替代品。催化剂将根据两个关键参数进行优化：过氧化氢生产率（给定电量产生多少过氧化氢）和过氧化氢选择性（所需过氧化氢产物与不需要的水副产物的相对比例）。为了实现高生产率和选择性，将开发一种能够精确控制催化剂纳米颗粒（尺寸为几十亿分之一米）的几何和电子特性的策略。这种方法将利用化学来制备催化剂结构，其大小从单个金属原子到一个原子厚的完整层，并由核心的纳米颗粒支撑提供电子控制。李博士的研究和教育活动紧密结合，将通过吸引高中到研究生院的学生，培养下一代电化学和电池研究人员。一项名为“电池设计挑战”的实验室活动将与普渡大学的AP周五项目合作，面向高中AP化学学生。这项活动将把来自印第安纳州各地的高中生带到普渡大学校园来参加这个实验室挑战。在化学系化学催化项目的支持下，普渡大学的Christina W. Li教授将研究用于过氧化氢电合成的亚单层核壳纳米颗粒。过氧化物选择性氧还原催化剂通常包括贵金属合金纳米颗粒，其表面系综几何形状和电子元件与合金成分紧密相关。为了独立控制催化活性位点的氧化还原和几何性质，该项目将开发一种胶体配体交换沉积策略，以获得广泛可调的贵金属表面集合几何形状-从孤立的原子到小簇到大岛-在核壳纳米颗粒中。将研究金属前驱体吸附和电取代反应，以将贵金属壳层沉积到一系列核心纳米颗粒组合物上。在这两种情况下，前体复合物的空间体积和氧化还原电位将通过配体化学调节，以加强原子隔离和表面限制沉积。此外，operando光谱将用于表征核壳和单原子微观结构在电化学极化过程中的演变，以稳定最活跃和选择性的表面形态。通过独立控制贵金属表面原子的集合几何和电子特性，该项目旨在开发分子氧高效和选择性电化学还原成过氧化氢的基本结构机制原理。这些系统和精确的材料应该允许阐明高选择性的最佳系综尺寸和低过电位过氧化氢生产的最佳o结合强度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Christina W. Li of Purdue University is studying catalysts to efficiently prepare hydrogen peroxide directly from air and water using electricity. Hydrogen peroxide is an important commodity chemical that has widespread use in water purification and disinfection. In developing efficient catalysts, this project has the potential to enable small-scale, mobile production for deployment in infrastructure-poor areas. Manufacturing hydrogen peroxide from air and water is a sustainable alternative to the current hydrogen-based process. The catalysts are to be optimized for two key parameters: peroxide productivity (how much hydrogen peroxide is generated for a given amount of electrical energy) and peroxide selectivity (the relative ratio of desired hydrogen peroxide product compared to undesired water by-product). To achieve both high productivity and selectivity, a strategy that enables precise control over the geometric and electronic properties of catalyst nanoparticles (sizes on the order of a few billionths of a meter) will be developed. This approach will use chemistry to prepare catalyst structures ranging in size from single metal atoms to full layers one atom thick with the electronic control provided by the nanoparticle support at the core. Dr. Li's research and educational activities are closely integrated and will educate the next-generation of electrochemistry and battery researchers by engaging students from high school through graduate school. A laboratory activity, the “Battery Design Challenge”, will be developed that is geared toward high school AP Chemistry students in partnership with the AP Fridays program at Purdue University. This activity will bring high school students from across Indiana to Purdue’s campus to compete in this laboratory challenge.With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Christina W. Li of Purdue University will be studying submonolayer core-shell nanoparticles for the electrosynthesis of hydrogen peroxide. Catalysts for peroxide-selective oxygen reduction typically comprise noble metal alloy nanoparticles, in which surface ensemble geometry and electronics are tightly convoluted with the alloy composition. In order to independently control the redox and geometric properties of the catalytic active site, this project will develop a colloidal ligand-exchange deposition strategy to access broadly tunable noble metal surface ensemble geometries—ranging from isolated atoms to small clusters to large islands—in a core-shell nanoparticle. Both metal precursor adsorption and galvanic replacement reactions will be studied to deposit noble metal shells onto a range of core nanoparticle compositions. In both cases, the steric bulk and redox potential of the precursor complex will be tuned though ligand chemistry in order to enforce atom isolation and surface-limited deposition. In addition, operando spectroscopy will be performed to characterize how core-shell and single atom microstructures evolve during electrochemical polarization with the goal of stabilizing the most active and selective surface morphologies. By independently controlling the ensemble geometry and electronic properties of the noble metal surface atoms, this project seeks to develop fundamental structure-mechanism principles for the efficient and selective electrochemical reduction of molecular oxygen to hydrogen peroxide. These systematic and precise materials should permit for the elucidation of optimal ensemble sizes for high selectivity and optimal O-binding strengths for low overpotential peroxide production.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.