Enhancing the surface sensitivity of in-situ/operando characterization of palladium membranes through polarization modulation and synthesis of optically smooth palladium thin films

Lee, Garam; Easa, Justin; Jin, Renxi; Booth, A. D.; O’Brien, Casey P.

doi:10.1016/j.memsci.2021.119605

Cited by 6 publications

(5 citation statements)

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“…To better understand the structure and dynamics of P4VP and P2VP under cycloaddition reaction conditions, the molecular structure of the P4VP and P2VP catalysts was characterized during exposure to epichlorohydrin/CO 2 /N 2 gas mixtures using in situ PM-IRAS. PM-IRAS is a reflectance-mode infrared spectroscopy technique with high surface sensitivity that arises from the high frequency modulation of the polarization of the incident infrared light between s- and p-polarization, and the selective absorption of s- and p-polarized light by the surface (p) and bulk gas or liquid (p + s) species. , Prior to PM-IRAS measurements, the P4VP and P2VP polymer solutions were knife-cast onto reflective gold-coated slides, dried in ambient air overnight, and loaded into the reactor for PM-IRAS measurements. Epichlorohydrin/CO 2 /N 2 gas mixtures were then introduced into the reactor while the PM-IRAS spectra were recorded continuously for 4 h of the reaction.…”

Section: Resultsmentioning

confidence: 99%

“…In situ PM-IRAS measurements were performed using an experimental apparatus has been described in detail in a previous publication. 45 Briefly, the experimental apparatus consists of a Bruker Vertex 70 FTIR spectrometer with a Bruker PMA50XL external accessory and a liquid nitrogen cooled MCT detector. A Harrick RefractorReactor grazing angle accessory was positioned in the sample compartment of the PMA50XL external accessory.…”

Section: Methodsmentioning

confidence: 99%

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Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Jin

Easa

et al. 2023

J. Phys. Chem. C

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The cycloaddition of CO 2 with epoxides is a 100% atom economical reaction that utilizes CO 2 and produces valuable cyclic carbonate products. Organic bases are attractive catalysts for this reaction because of their green characteristics, such as low cost and low toxicity. However, further catalyst development is required to achieve acceptable yields at mild temperatures and pressures. This work aims to establish catalyst structure−performance relationships to accelerate the rational design of high performance organic base catalysts for the cycloaddition reaction. Toward this end, we investigate the influence of steric crowding at the ring nitrogen atom of a series of pyridine-based catalysts on the reaction mechanism and catalyst performance using batch reactor measurements at a mild temperature (57 °C) and atmospheric pressure under solventless conditions combined with in situ infrared spectroscopic characterization of the catalysts. We show that steric crowding at the ring nitrogen atom has a significant influence on the reaction mechanism and catalyst performance. Catalysts with unhindered access to the ring nitrogen atom, such as pyridine, 4vinylpyridine, 3-vinylpyridine, and poly(4-vinylpyridine), are completely transformed during the cycloaddition reaction by quaternization from the epoxide reactant, producing zwitterionic pyridinium-epoxide adducts and ammonium salts that precipitate out of solution. Catalysts with hindered access to the ring nitrogen atom, such as 2-vinylpyridine and poly(2-vinylpyridine), resist quaternization from the epoxide reactant due to the high degree of steric hindrance at the ring nitrogen atom. The poly(2vinylpyridine) catalyst in particular displayed high stability, high product selectivity, and high activity for cyclic carbonate synthesis. These molecular-level insights have significant implications for the rational design of active, stable, and metal-free catalysts for cyclic carbonate synthesis by tuning the steric crowding at the active site.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Jin

Easa

et al. 2023

J. Phys. Chem. C

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“…Separation of H 2 from dense metallic membranes occurs in three steps: 1 - dissociative adsorption of H 2 on the upstream side of the membrane, 2 - diffusion of H atom through the interstitial space within the bulk metal, 3 - recombinative desorption of H 2 from the downstream side of the membrane. Considering this process as a whole reveals Pd as the prime candidate for membrane material due to its high H 2 activity and near-infinite permselectivity [ 2 , 10 – 12 ]. However, the cost of Pd poses a challenge, prompting researchers to focus on fabricating thin palladium layers (1–15 μm) on support materials/substrates, which increases the mechanical stability of the membrane [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…To overcome this limitation, an intermediate layer can be introduced to reduce the pore size and ensure a narrow pore size distribution on the alumina surface [ 13 , 17 , 20 ]. Among the various intermediate layers explored, γ-Al 2 O 3 has been frequently utilized [ 12 , 21 – 23 ].…”

Section: Introductionmentioning

confidence: 99%

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces

GÜR,

TOPRAK

2024

Turkish Journal of Chemistry

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Dense metallic membranes, especially Pd and Pd alloys, have been intensely investigated to provide an alternative and economical way to obtain H 2 with ultrahigh purity. To overcome the high cost of Pd, composite membrane structures that comprise a thin layer of Pd are utilized. However, it is a challenge to obtain a thin, dense, and uniform Pd layer on the support materials. This study investigates the parametric analysis of γ-Al 2 O 3 interlayer formation and the electroless Pd plating (Pd ELP) procedures on α-Al 2 O 3 supports with the aim to achieve a thin, uniform Pd surface without annealing. Adjustments in PEG/PVA concentration, dipping time, and heat treatment enabled creating a thin γ-Al 2 O 3 interlayer on α-Al 2 O 3 , minimizing pore size and density. Hydrazine concentration, heat treatment, and bath temperature were adjusted to optimize Pd ELP to achieve maximum yield from the plating bath and a dense, uniform surface without annealing. Pd/γ-Al 2 O 3 /α-Al 2 O 3 structures were analyzed using scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis to observe the impact of varied parameters on surface structures. Optimized sample was compared to an annealed Pd/α-Al 2 O 3 prepared in accordance with literature methods and a Pd/graphite/α-Al 2 O 3 sample to validate the use of optimized ELP procedure and the γ-Al 2 O 3 interlayer. Results show that a dense and uniform 13 μm Pd coating was achieved on a γ-Al 2 O 3 -coated α-Al 2 O 3 support without annealing, using three fresh ELP baths. This was done using sequential hydrazine addition with a decreased concentration (1 M) into the ELP baths at 30 °C, and applying heat treatment at 120 °C between each fresh ELP bath.

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“…× 10 4 H 2 vs N 2 with a good plating yield and cycling stability level that make it competitive for practical use.More recent work by O'Brien and co-workers389 has provided an improved process resulting in an optically smooth EL Pd film (i.e., roughness ∼ 0.39 μm) on Al 2 O 3 substrates. In their work, substrate activation involves 6 cycles of successive immersions in SnCl 2 /HCl and Pd(NO 3 ) 2 /HCl solutions with intervening H 2 O rinses.…”

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confidence: 99%

Electroless Metallization of the Elements: Survey and Progress

Turró

Dressick

2022

ACS Appl. Electron. Mater.

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The electroless plating of metals and their alloys, oxides, and chalcogenides represents a critically important technology for the automotive, aerospace, machine tools, and, especially, the electronics industries. Since the initial efforts involving the plating of industrially important metals, such as Ni, Co, Cu, Ag, and Au, in the mid-20th century, the process has evolved to encompass a growing number of elements. At the same time, this expansion in the palette of accessible metals has enabled progress in these industries and evoked new nonconventional applications. In this review, we collect and survey available electroless processes in aqueous and organic solvent systems for each element organized according to position in the Periodic Table as a resource for the reader. Examples illustrating progress in the field are presented and are described in sufficient detail to be useful and understandable for both the expert and nonexpert. Given the historical importance of electronics as a driver for development of electroless processes, examples are electronics-related where possible. However, we strive to also include examples of applications in nontraditional fields to provide the reader with a sense of generality available for electroless methods. The review closes with an outlook for the field and a challenge to scientists and engineers to adapt electroless processes for new applications to continue the growth of the field.

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Enhancing the surface sensitivity of in-situ/operando characterization of palladium membranes through polarization modulation and synthesis of optically smooth palladium thin films

Cited by 6 publications

References 58 publications

Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces

Electroless Metallization of the Elements: Survey and Progress

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Enhancing the surface sensitivity of in-situ/operando characterization of palladium membranes through polarization modulation and synthesis of optically smooth palladium thin films

Cited by 6 publications

References 58 publications

Cycloaddition of CO2 to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Cycloaddition of CO2 to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces

Electroless Metallization of the Elements: Survey and Progress

Contact Info

Product

Resources

About

Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

Cycloaddition of CO₂ to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism