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

非技术描述：晶格应变是由晶体缺陷引起的一种重要的材料改性现象，它通过改变催化剂表面功函数来改变表面吸附行为，可以给催化剂带来许多新的优点。对于贵金属基的超小颗粒，即纳米晶体，控制晶格应变可能是提高其化学和电化学反应催化性能的重要途径之一。本项目主要研究通过气相蚀刻方法产生的双金属纳米晶体中的晶格应变。其中一种被提议的材料是Pt-Ni纳米晶体系统，其中ni成分通过与一氧化碳结合在温和的温度下形成气态羰基镍而被提取出来，从而在纳米晶体中产生应变。通过这一晶格应变概念，本研究旨在寻求对能量转化和环境保护中的一些紧急电化学反应（如燃料电池反应、水裂解反应、碳中性转化反应）中晶格应变形成的一些基本认识和催化改进的解决方案。具体而言，本研究将回答以下问题：在脱合金过程中如何产生和控制晶格应变？如何明确地确定晶格应变？在实验中如何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项目产生深远的影响。从这项研究中获得的见解和知识将刺激美国国家科学基金会支持的S-STEM项目、宾厄姆顿大学的“跨学科卓越领域”运动和新课程开发。本计划亦将透过暑期研究计划，促进研究生及本科生的实验室训练活动，连结不同研究领域。此外，这项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。技术描述：对于贵金属纳米晶体，晶格应变一般会导致晶格收缩，其中心d带下移，从而削弱了催化剂表面上物质的吸附强度。该项目的目标是显著推进晶格应变催化位点的发展，晶格应变存在于几种类型的形状控制的最先进的纳米晶体中作为模型系统。利用Mond工艺作为一种前所未有的蚀刻工艺，可以从含ni的双金属前驱体中创建晶格应力系统。通过对气体脱合金过程产生的高多孔纳米框架的系统结构分析，将深入了解相关的脱合金机制。通过使用几种典型反应（包括但不限于ORR、HER和eCO2RR）对其电催化性能进行评估，将在有应变应力和没有应变应力的情况下对已确定的性能进行比较，并揭示反应性-应变相关性，为调整电催化活性提供指导。所提出的Pt-Ni前驱体也将扩展到其他双金属体系，如Cu-Ni， Ag-Ni， Pd-Ni和含铁双金属体系。该项目将对探索催化活性的机理起源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。

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.