A5045854318- Catalytic Processes in Materials Science
- Catalysis and Oxidation Reactions
- Electrocatalysts for Energy Conversion
- Catalysts for Methane Reforming
- Nanomaterials for catalytic reactions
- Catalysis and Hydrodesulfurization Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Electron and X-Ray Spectroscopy Techniques
- Catalysis for Biomass Conversion
- Metal-Organic Frameworks: Synthesis and Applications
- Zeolite Catalysis and Synthesis
- Machine Learning in Materials Science
- Electrochemical Analysis and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Asymmetric Hydrogenation and Catalysis
- Advanced Photocatalysis Techniques
- X-ray Diffraction in Crystallography
- Advanced Chemical Physics Studies
- nanoparticles nucleation surface interactions
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Nanocluster Synthesis and Applications
- Ionic liquids properties and applications
- Carbon dioxide utilization in catalysis
- Hydrogen Storage and Materials
SLAC National Accelerator Laboratory
2016-2025
Stanford Synchrotron Radiation Lightsource
2017-2025
Menlo School
2018-2024
Stanford University
2022-2024
University of California, Davis
2015-2018
University of California System
2017
King Abdullah University of Science and Technology
2016
Utrecht University
1993
University of Washington
1992
CO2 reduction to higher value products is a promising way produce fuels and key chemical building blocks while reducing emissions. The reaction at atmospheric pressure mainly yields CH4 via methanation CO the reverse water-gas shift (RWGS) reaction. Describing catalyst features that control selectivity of these two pathways important determine formation specific products. At same time, identification morphological changes occurring catalysts under conditions can be crucial tune their...
Catalysts consisting of atomically dispersed Pt (Ptiso) species on CeO2 supports have received recent interest due to their potential for efficient metal utilization in catalytic convertors. However, discrepancies exist between the behavior (reducibility, interaction strength with adsorbates) high surface area Ptiso/CeO2 systems and well-defined science computational model systems, suggesting differences local coordination two classes materials. Here, we reconcile these by demonstrating that...
Atomically dispersed noble metal catalysts have drawn wide attention as candidates to replace supported clusters and nanoparticles. Atomic dispersion can offer unique chemical properties well maximum utilization of the expensive metals. Addition a second has been found help reduce size Pt ensembles in bimetallic clusters; however, stabilization isolated atoms small nests nonprecious remains challenging. We now report novel strategy for design, synthesis, characterization zeolite-supported...
The atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity. Therefore, understanding site stability evolution under different reaction conditions key design efficient robust catalysts. Herein we describe theoretical calculations which predict that carbon monoxide can be used stabilize geometries bimetallic alloys then demonstrate experimentally same PdAu catalyst transitioned between a single-atom alloy Pd cluster phase. Each...
Abstract A single‐atom Pt 1 /CeO 2 catalyst formed by atom trapping (AT, 800 °C in air) shows excellent thermal stability but is inactive for CO oxidation at low temperatures owing to over‐stabilization of 2+ a highly symmetric square‐planar O 4 coordination environment. Reductive activation form nanoparticles (NPs) results enhanced activity; however, the NPs are easily oxidized, leading drastic activity loss. Herein we show that tailoring local environment isolated thermal‐shock (TS)...
Single-atom catalysts (SACs), consisting of individual metal atoms dispersed on a support, attract attention due to their unique reactivity, efficient use precious metals, and precise chemical tunability. Characterization the species is crucial substantiate structure–function relationships. Authors often use─and referees require─X-ray absorption spectroscopy (XAS) data prove absence clustered (or oxide) structures after pre-treatment under in situ or operando conditions. However, there has...
Single atoms of platinum group metals on CeO2 represent a potential approach to lower precious metal requirements for automobile exhaust treatment catalysts. Here we show the dynamic evolution two types single-atom Pt (Pt1) CeO2, i.e., adsorbed Pt1 in Pt/CeO2 and square planar PtATCeO2, fabricated at 500 °C by atom-trapping method 800 °C, respectively. Adsorbed is mobile with situ formation few-atom clusters during CO oxidation, contributing high reactivity near-zero reaction order CO. In...
Bimetallic catalytic materials are in widespread use for numerous reactions, as the properties of a monometallic catalyst often improved upon addition second metal. In studies with bimetallic catalysts, it remains challenging to establish clear structure–property relationships using traditional impregnation techniques, due presence multiple coexisting active phases different sizes, shapes, and compositions. this work, convenient approach prepare small uniform Pt/Pd nanocrystals tailorable...
Selective oxidations are crucial for the creation of valuable chemical building blocks but often require expensive and unstable stoichiometric oxidants such as hydroperoxides peracids. To date, many catalysts that contain a single type active site have not been able to attain desired level selectivity partially oxidized products over total combustion. However, containing multiple types sites proven be successful selective reactions. One category is bimetallic alloys, in which catalytic...
Determining and controlling the uniformity of isolated metal sites on surfaces supports are central goals in investigations single-site catalysts because well-defined species provide opportunities for fundamental understanding surface sites. CO is a useful probe sites, often reacting with them to form carbonyls, infrared spectra which insights into nature metal-support interface. Metals bonded various support give broad bands spectra, when narrow observed, they indicate high degree Much...
Abstract Although Cu/ZnO-based catalysts have been long used for the hydrogenation of CO 2 to methanol, open questions still remain regarding role and dynamic nature active sites formed at metal-oxide interface. Here, we apply high-pressure operando spectroscopy methods well-defined Cu 0.7 Zn 0.3 nanoparticles supported on ZnO/Al O 3 , γ-Al SiO correlate their structure, composition catalytic performance. We obtain similar activity methanol selectivity Cu/ZnO/Al CuZn/SiO but yield decreases...
Metal organic frameworks (MOFs), with their crystalline, porous structures, can be synthesized to incorporate a wide range of catalytically active metals in tailored surroundings. These materials have potential as catalysts for conversion light alkanes, feedstocks available large quantities from shale gas that are changing the economics manufacturing commodity chemicals. Mononuclear high-spin (S = 2) Fe(II) sites situated nodes MOF MIL-100(Fe) convert propane via dehydrogenation,...
Recent work has exploited the ability of metal-organic frameworks (MOFs) to isolate Fe sites that mimic structures in enzymes catalyze selective oxidations at low temperatures, opening new pathways for valorization underutilized feedstocks such as methane. Questions remain whether radical-rebound mechanism commonly invoked enzymatic and homogeneous systems also applies these rigid-framework materials, which resisting overoxidation desired products is a major challenge. We demonstrate MOFs...
Single-atom catalysts (SACs) often exhibit dynamic responses to the reaction and pretreatment environment that affect their activity. The lack of understanding these behaviors hinders development effective, stable SACs, makes investigations rather difficult. Here we report a reduction–oxidation cycle induces nearly 5-fold activity enhancement on Pt/TiO2 SACs for reverse water–gas shift (rWGS) reaction. We combine microscopy (STEM) spectroscopy (XAS IR) studies with kinetic measurements,...
The effect of dynamic reorganization and confinement isolated TiIV catalytic centers supported on silicates is investigated for olefin epoxidation. Active sites consist grafted single-site calix[4]arene-TiIV or their calcined counterparts. Their location synthetically controlled to be either unconfined at terminal T-atom positions (denoted as type-(i)) within confining 12-MR pockets type-(ii); diameter ∼7 Å, volume ∼185 Å3) composed hemispherical cavities the external surface zeotypes with...
Methanol carbonylation to acetic acid (AA) is a large-scale commodity chemical production process that requires homogeneous liquid-phase organometallic catalysts with corrosive halide-based cocatalysts achieve high selectivity and activity. Here, we demonstrate heterogeneous catalyst based on atomically dispersed rhenium (ReO4) active sites an inert support (SiO2) for the halide-free, gas phase of methanol AA. Atomically ReO4 species nanometer sized ReOx clusters were deposited surface area...
CeO2-supported Pt single-atom catalysts have been extensively studied due to their relevance in automobile emission control and for the fundamental understanding of CeO2-based catalysts. Though nanoparticles are often more active than counterparts, former could easily redisperse single atom under oxidizing diesel conditions. Therefore, maximize reactivity every atom, it is important fully understand reaction mechanism atoms. Here, we report a CO oxidation study on Pt/CeO2 catalyst, where can...
Iron-based catalysts are considered active for the hydrogenation of CO2 toward high-order hydrocarbons. Here, we address structural and chemical evolution oxide-supported iron nanoparticles (NPs) during activation stages reaction. Fe NPs were deposited onto planar SiO2 Al2O3 substrates by dip coating with a colloidal NP precursor physical vapor deposition Fe. These model studied in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) pure O2, then H2, finally + H2 (1:3)...
The electrochemical nitrate reduction reaction (NO3RR) on titanium introduces significant surface reconstruction and forms hydride (TiHx, 0 < x ≤ 2). With ex situ grazing-incidence X-ray diffraction (GIXRD) absorption spectroscopy (XAS), we demonstrated near-surface TiH2 enrichment with increasing NO3RR applied potential duration. This quantitative relationship facilitated treatment of Ti to form TiH2/Ti electrodes for use in NO3RR, thereby decoupling formation from performance. A wide range...
Propene and 1,3-butadiene are important building-block chemicals that can be produced by dehydrogenation of propane butane on Pt catalysts. A challenge is to develop highly active selective catalysts resistant deactivation sintering coke formation. We have recently shown (Qi , J. Am. Chem. Soc. 2021, 143, 21364−21378) these objectives met for (PDH) using atomically dispersed anchored neighboring ≡SiOZn-OH groups bonded the framework dealuminated zeolite BEA. In present study, we demonstrate...