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，克里斯蒂娜W。普渡大学的李博士正在研究利用电力直接从空气和水有效制备过氧化氢的催化剂。过氧化氢是一种重要的日用化学品，广泛用于水净化和消毒。在开发高效催化剂方面，该项目有可能使小规模、移动的生产能够在基础设施薄弱地区进行。从空气和水中生产过氧化氢是目前氢基工艺的可持续替代方案。催化剂将针对两个关键参数进行优化：过氧化物生产率（对于给定量的电能产生多少过氧化氢）和过氧化物选择性（所需过氧化氢产物与不需要的水副产物的相对比率）。为了实现高生产率和高选择性，将开发一种能够精确控制催化剂纳米颗粒（尺寸为数十亿分之一米）的几何和电子特性的策略。这种方法将使用化学方法来制备催化剂结构，其尺寸从单个金属原子到一个原子厚的完整层，由核心处的纳米颗粒载体提供电子控制。李博士的研究和教育活动是紧密结合的，将通过吸引高中到研究生院的学生来教育下一代电化学和电池研究人员。一个实验室活动，“电池设计挑战赛”，将开发面向高中AP化学学生与普渡大学AP星期五计划合作。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，参加这项实验室挑战赛。李博士将研究用于过氧化氢电合成的亚单层核壳纳米粒子。用于过氧化物选择性氧还原的催化剂通常包含贵金属合金纳米颗粒，其中表面系综几何形状和电子学与合金组合物紧密卷积。为了独立控制氧化还原和催化活性位点的几何性质，本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。将研究金属前体吸附和原电池置换反应以将贵金属壳存款到一系列核纳米颗粒组合物上。在这两种情况下，前体络合物的空间体积和氧化还原电位将通过配体化学进行调整，以加强原子隔离和表面限制沉积。此外，操作光谱将进行表征核壳和单原子微结构如何在电化学极化过程中演变，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系综几何结构和电子性质，该项目旨在开发有效和选择性电化学还原分子氧为过氧化氢的基本结构-机理原理。这些系统和精确的材料应允许阐明高选择性的最佳整体尺寸和低过电位过氧化物生产的最佳O-结合强度。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.