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

非技术描述：晶格应变是一种重要的材料改性现象，它通过改变催化剂的表面功函数来改变催化剂的表面吸附行为，从而为催化剂带来许多新的优点。对于贵金属基超细粒子，即纳米晶，晶格应变的调控是提高其在化学反应和电化学反应中催化性能的重要途径之一。本项目的重点是研究双金属纳米晶中存在的晶格应变，这些纳米晶是通过气相腐蚀方法产生的。其中一种材料是铂-镍纳米晶体系，通过与一氧化碳在温和的温度下结合形成气态的羰基镍，从而在纳米晶体中产生应变，从而从该纳米晶体中提取镍成分。通过这个晶格应变的概念，本研究旨在寻求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、水分解反应和碳中性转化中的晶格应变形成和催化改进的一些基本认识和解决方案。具体地说，本研究将回答以下问题：如何在非合金化过程中产生和控制晶格应变？怎样才能明确地识别晶格应变呢？如何在实验上使用晶格应变来促进反应性？该项目将通过多学科研究平台对正在进行的各种外展和教育项目产生深远影响。从这项研究中获得的见解和知识将促进由国家科学基金会资助的S-STEM项目、宾厄姆顿大学的“跨学科卓越领域”活动和新课程的开发。该项目还将通过暑期研究项目，通过在不同研究领域之间建立联系，促进研究生和本科生的实验室培训活动。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好处。技术描述：对于贵金属纳米晶体，晶格应变通常会导致以d带中心下移为特征的晶格收缩，从而削弱物种在催化剂表面的吸附强度。该项目的目标是以几种形状可控的最先进的纳米晶体中存在的晶格应变作为模型系统，显著推进催化中心的开发。通过利用蒙德工艺作为一种史无前例的刻蚀协议，可以从含镍的双金属前驱体创建晶格应力系统。通过对气态脱合金化过程中产生的高孔纳米膜进行系统的结构分析，将深入了解相关的脱合金化机理。通过使用几个典型反应(包括但不限于ORR、HER和eCO2RR)对它们的电催化性能进行评估，将对有和没有应变应力的识别性能进行比较，并发现为调整电催化活性提供指导的反应性-应变相关性。所提出的铂-镍前驱体还将扩展到其他双金属系统，如铜-镍、银-镍、钯-镍和含铁双金属系统。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影响。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势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.