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.
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.
