Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.langmuir.5c01016

Other Link： https://pubs.acs.org/doi/10.1021/acs.langmuir.5c01016

Language：English   Publisher：Journal of Physical Chemistry Letters  

In situ X-ray absorption spectroscopy (XAS) is a powerful tool to probe the electronic and structural properties of materials under operating conditions. However, its bulk-sensitive nature often obscures the surface-specific dynamics critical to understanding catalytic processes. We herein demonstrate successful extraction of surface dynamics from bulk XAS spectra by applying modulation excitation spectroscopy to XAS (ME-XAS). Methane oxidation over Pt/Al<inf>2</inf>O<inf>3</inf> was chosen as a model reaction to verify the strength of ME-XAS for extracting surface dynamics of Pt nanoparticles of different sizes. ME-XAS spectra revealed that during methane oxidation, only surface Pt atoms were repeatedly oxidized and reduced while the bulk Pt remained mostly metallic. Samples with low Pt loadings were more oxidizable and showed lower methane oxidation activity, in line with metallic Pt being more active for methane dissociation than Pt oxides. This study underscores the potential of ME-XAS to enhance our understanding of surface-bulk dynamics and rationalize catalytic phenomena, offering a pathway to the development of more efficient and selective catalysts.

DOI： 10.1021/acs.jpclett.5c00380

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PubMed

Publisher：ACS Sustainable Chemistry and Engineering  

This study aimed to design materials for CO<inf>2</inf> capture with low regeneration temperatures without compromising the adsorption capacity (AC). Branched polyethylenimine (BPEI) functionalized with acrylonitrile (AN), 2-ethylhexyl acrylate (EHA), and butyl acrylate (BA) was impregnated onto fumed silica and tested for its adsorption and desorption properties. Higher functionalization degrees led to decreased desorption temperatures (DTs) from 73 to 97 °C to as low as 25 °C, which was attributed to the higher percentages of secondary amines upon functionalization and changes in the CO<inf>2</inf> adsorption mechanism. However, the adsorption capacities also decreased with functionalization. Bayesian optimization using machine learning models predicted optimal compositions of adsorbents for high adsorption capacities at low regeneration temperatures. The isothermal operation of CO<inf>2</inf> capture and release was also demonstrated to lower the energy requirement for CO<inf>2</inf> capturing systems. The functionalized BPEI materials steadily adsorb and release CO<inf>2</inf> for 20 cycles under isothermal conditions without any deterioration of the performance. BPEI 10,000 functionalized with AN, EHA, and BA offers a promising balance between AC and DT, making it suitable for industrial applications.

DOI： 10.1021/acssuschemeng.5c01250

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Publisher：Journal of Catalysis  

Cyclic and repeatable CO<inf>2</inf>/H<inf>2</inf> formation under periodic CO ↔ H<inf>2</inf>O feeds, that is unsteady-state water–gas shift reaction (uss-WGS), was found to be catalyzed by a gold nanoparticles-loaded CeO<inf>2</inf> (Au/CeO<inf>2</inf>) catalyst. Kinetics of the CO-reduction of Ce⁴⁺ to Ce³⁺ and Ce³⁺ reoxidation by H<inf>2</inf>O in combination with transient CO<inf>2</inf>/H<inf>2</inf> formation over Au/CeO<inf>2</inf> were studied by operando ultraviolet–visible (UV–vis) and infrared (IR) spectroscopies at 175 °C. The Ce⁴⁺–OH species were reduced by CO to give Ce³⁺-□-Ce³⁺ (□: oxygen vacancy) and gas phase products (H<inf>2</inf>, CO<inf>2</inf>). The Ce³⁺-□-Ce³⁺ species were oxidized by H<inf>2</inf>O to give H<inf>2</inf> and Ce⁴⁺–OH species. The reduction and reoxidation rates of Ce⁴⁺/Ce³⁺ redox couple were close to the rates of transient CO<inf>2</inf>/H<inf>2</inf> formation. The X-ray absorption spectroscopy results showed that the oxidation states of Au remained unchanged during the redox reactions. These results indicate that the uss-WGS is primary driven by the Ce⁴⁺/Ce³⁺ redox couple. Combined with the observation of adsorbed carboxylate intermediates as a precursor of H<inf>2</inf> and CO<inf>2</inf>, associative redox mechanism is proposed as the main pathway for the unsteady-state WGS reaction on Au/CeO<inf>2</inf> at 175 °C.

DOI： 10.1016/j.jcat.2024.115500

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Scopus

Publisher：Materials Advances  

Perovskite oxides with a low cost and high catalytic activity are considered as suitable candidates for the oxygen evolution reaction (OER)/oxygen reduction reaction (ORR), but most of them favour only either the ORR or the OER. Besides, their underlying catalytic mechanisms are subject of an ongoing debate. Herein, La0.8Sr0.2CoO3-δ (LSC) was selected as a base perovskite oxide for doping different elements into its B-site to fabricate four different La0.8Sr0.2Co0.8M0.2O3-δ (LSCM; M = Ni, Fe, Mn, and Cu) perovskite oxides. Among the catalysts tested with and without multi-walled carbon nanotubes (MWNTs), La0.8Sr0.2Co0.8Fe0.2O3-δ (LSCF) outperformed any other catalysts in terms of both OER and ORR activity. The OER/ORR activity enhancement with LSCF is also discussed based on spectroscopic and microscopic analyses and lattice oxygen transportation.

DOI： 10.1039/d1ma00632k

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Scopus

Language：English   Presentation type：Poster presentation  

Venue：九州大学   Country：Japan  

Language：English   Presentation type：Poster presentation  

Venue：九州大学   Country：Japan  

Language：Japanese   Presentation type：Poster presentation  

Venue：関西大学   Country：Japan  

Language：Japanese   Presentation type：Poster presentation  

Venue：大阪大学   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学   Country：Japan