Understanding and Predicting Reactivity and Selectivity of Supported Few Atom Catalysts through Control of their Local Environment

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Rahman of University of Central Florida, Professor Liu of University of California Riverside, and Professor Hong of Brewton Parker College are studying the fundamental properties of singly dispersed metal-atom (Pt, Ag, Cu, and Co) catalysts. The work will provide a comprehensive understanding of factors that control catalyst activity and selectivity in hydrogen production from methanol and ammonia decomposition.

Rates and for these reactions will be determined and correlated to the electronic and geometric structure of the local atomic environment of the single atom catalyst. This systemic coupling between theory and experiment will expose reaction mechanisms and help set guidelines for the rational design of cost-effective catalysts for these reactions of technological importance.

The outcome of the project is expected to impact industrial methodologies and society broadly through strategies for the development of cost-effective catalysts and the training of the work force to enable these transformative changes in catalyst design. The PIs will train students in interdisciplinary research. UCF being an HIS is ideally suited for recruitment and integration of disadvantaged minority individuals in STEM fields.

The team will also involve students from Brewton-Parker College (BPC), with a 46% population of first-generation college students and/or from disadvantaged groups, and who have few research opportunities. A summer Research Experiences for Undergraduates (REU) program will be proposed to attract students, particularly those from underrepresented minority (URM) groups.

The PI will leverage her position as the site leader for American Physical Society Bridge Program to recruit URM graduate students to work on the proposed research. Existing international collaborations of the PIs will help extend the outcomes of the proposed work globally. The PIs will continue to engage in community-outreach activities, making use also of the infrastructure provided by PhysTEC (Physics Teacher Education Coalition) Comprehensive site at UCF which facilitates strong interactions with K-12 students and teachers in the greater Orlando area. The PI will reach out to similar K-12 communities in Riverside and Mount Vernon.

In addition to a tightly coupled effort in experiments and ab initio modeling and simulation, we are developing machine learning potentials to carry out extended simulations under experimental conditions that facilitate a deep understanding of reaction mechanisms as affected by catalyst dynamical transformations. Research components include a tight coupling among the following tasks: 1) high-throughput screening of metal and oxide-support combinations of candidate nanocatalysts; 2) determination of stability criteria of candidate nanocatalysts via thermodynamics-assisted, density functional theory (DFT)-based phase diagram calculations; 3) development of DFT-assisted ML potentials for calculation of X-ray photoelectron spectra (XPS) and X-ray absorption spectra (XAS) under relevant conditions; 4) synthesis of proposed nanocatalysts; 5) application of scanning transmission electron microscopy (STEM) and XAS to confirm the singly-dispersed status of targeted systems; 6) determination of reaction rates and turnover frequencies; 7) application of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for identifying catalyst structure and revealing reaction mechanisms.

We use a feedback loop between theory and experiment to obtain an understanding of reaction mechanisms and insights into factors such charge transfer, strain, etc. that control site activity. The project will thus expose competing reaction pathways (and reaction intermediates) responsible for product selectivity, thereby providing design control. Comparison of calculated and observed surface structure, reaction rates and turnover frequencies will validate the theoretical approach and refine experimental parameters.

The immediate outcome will be paradigm-shifting strategies for predicting and controlling reactivity of atomically dispersed catalysts, as a function of local coordination environment.

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.