Manipulating and Exploiting Lattice Strain as a Novel Platform to Tune the Surface Work Function of Metallic Nanocatalysts

非技术描述：晶格应变，由晶体缺陷引起，是材料改性的一个重要现象，可以给催化剂带来许多新的优点，因为它通过改变催化剂表面功函数改变表面吸附行为。对于贵金属基超小颗粒，即纳米晶体，晶格应变的操纵可能是改善其化学和电化学反应催化性能的重要途径之一。本计画主要研究以气相蚀刻法制造的奈米微晶中存在的晶格应变。所提出的材料之一是Pt-Ni氧化物系统，通过在温和温度下与一氧化碳结合以形成气态羰基镍，从而在氧化物中产生应变，从该系统中提取Ni组分。通过晶格应变的概念，对能源转换和环境保护中的一些新兴电化学反应，如燃料电池反应、水裂解反应、碳中性转化反应等，寻求晶格应变形成的基本认识和催化改进的解决方案。具体来说，这项研究将回答以下问题：如何可以产生晶格应变和控制在去合金化过程中？如何明确地确定晶格应变？如何在实验中利用晶格应变来提高反应性？该项目将通过多学科研究平台对各种正在进行的推广和教育计划产生深远的影响。从这项研究中获得的见解和知识将刺激NSF支持的S-STEM计划，宾厄姆顿大学的“跨学科卓越领域”活动和新的课程开发。该项目还将通过夏季研究计划，加强不同研究领域之间的联系，促进研究生和本科生的实验室培训活动。此外，该研究的成功将通过科学发现和由此产生的技术为公众带来多重利益。技术说明：对于贵金属纳米晶体，晶格应变通常会导致晶格收缩，其特征是d带中心下移，这削弱了物种在催化剂表面的吸附强度。该项目的目标是显着推进催化位点的发展与晶格应变，存在于几种类型的形状控制的国家的最先进的纳米晶体作为模型系统。晶格应力系统可以通过利用Mond工艺作为前所未有的蚀刻协议从含Ni的Ni-Cu前体产生。相关的去合金化机制将深入理解，通过系统的结构分析的高度多孔的纳米框架产生的气体去合金化过程。通过使用几种典型反应（包括但不限于ORR、HER和eCO 2 RR）评估其电催化性能，将对有和没有应变应力的情况下确定的性能进行比较，并发现提供指导方针的反应性-应变相关性调整电催化活性。本文所提出的Pt-Ni前驱体也将被推广到其他的金属间化合物体系，如Cu-Ni、Ag-Ni、Pd-Ni和含Fe的金属间化合物体系。该项目将对催化活性的机械起源的开发以及电催化性能改进的新见解产生深远的影响。该奖项反映了NSF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。

Nontechnical description:Lattice strain, arising from crystal imperfections, is an important phenomenon of material modification and can bring many novel advantages to catalysts as it changes the surface adsorption behavior through a variation of the catalyst surface work function. For noble metal-based ultra-small particles, that is, nanocrystals, manipulation of the lattice strain could be one of the significant pathways to improve their catalytic performance on chemical and electrochemical reactions. This project focuses on the study of the lattice strain existing in bimetallic nanocrystals that are produced via a gas-phase etching approach. One of the proposed materials is a Pt-Ni nanocrystal system from which the Ni-component is extracted by combining with carbon monoxide to form gaseous nickel carbonyl at a mild temperature, thus creating a strain in the nanocrystal. Through this lattice strain concept, the research aims to seek some fundamental understandings of the lattice strain formation and solutions of catalytic improvement in some emergent electrochemical reactions in energy conversion and environmental protection, such as reactions in fuel-cell, water-splitting, and carbon-neutral conversion. Specifically, this study will answer the following questions: How can the lattice strain be generated and controlled during a de-alloying process? How can the lattice strain be explicitly identified? And how can the lattice strain be used experimentally to promote the reactivity? This project will have profound impacts on various ongoing outreach and education programs through multidisciplinary research platform. The insights and knowledge gained from this study will stimulate the NSF-supported S-STEM program, Binghamton University's "Transdisciplinary Area of Excellence" campaign, and novel curriculum development. This project will also promote lab-based training activities of graduate and undergraduate students through summer research programs by forging links among diverse research fields. In addition, the success of this study will bring multifold benefits to the general public through scientific discoveries and resultant technologies.Technical description:For noble metal nanocrystals, lattice strain can generally cause a lattice contraction featuring a down-shift d-band center, which weakens the adsorption strength of species on the catalyst surfaces. The goal of this project is to significantly advance the development of catalytic sites with lattice strain that exists in several types of shape-controlled state-of-the-art nanocrystals as the model systems. The lattice-stressed systems can be created from Ni-containing bimetallic precursors by taking advantage of the Mond process as an unprecedented etching protocol. The related de-alloying mechanism will be understood in depth through a systematical structure-analysis of the highly porous nanoframes generated from a gaseous de-alloying process. With an evaluation of their electrocatalytic performance using several typical reactions including but not limited to ORR, HER, and eCO2RR, a comparison of the identified performances with and without the strain stress will be implemented, and a reactivity-strain correlation that provides guidelines for tuning electrocatalytic activity will be uncovered. The proposed Pt-Ni precursor will also be extended to other bimetallic systems, such as Cu-Ni, Ag-Ni, Pd-Ni, and Fe-containing bimetallic system. This project will have profound impacts on the exploitation of mechanistic origin of the catalytic activity as well as novel insights of the electrocatalytic performance improvement.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.