Improved experimental setup for in situ UV-vis-NIR spectroscopy under catalytic conditions

Melsheimer, Jörg; Thiede, M.; Ahmad, Rafat; Tzolova-Müller, Genka; Jentoft, Friederike C.

doi:10.1039/b304039a

Cited by 12 publications

(3 citation statements)

References 19 publications

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“…A cooling air blower was used only for prolonged DR measurements at the high (650-720 K) temperatures when the assembly was filled with oxygen at a pressure P ≥ 1 Torr. By comparison, in the study reported by Melsheimer and coworkers, 10 heating of the integrating sphere in the Lambda 9 Perkin-Elmer spectrophotometer that accompanied DR measurements at high temperatures (673 K) was suppressed by mounting either a highly reflecting tube (12 mm long) or else a quartz light conductor between the sphere and the sample; under these conditions, the DR signal in such an accessory was only 20-45% relative to the reference beam.…”

Section: The Cryostat Accessorymentioning

confidence: 84%

In situ study of photo- and thermo-induced color centers in photochromic rutile TiO2 in the temperature range 90–720 K

Кузнецов

Glazkova

Mikhaylov

et al. 2016

Photochem Photobiol Sci

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This article reports an in situ UV-Vis-NIR diffuse reflectance (DR) spectroscopic and kinetic study of the photoformation and thermal annealing of light absorbing electronic point defects (color centers) in photochromic TiO in the temperature range 90-720 K using a simple laboratory-made cryostat-type accessory (for a Cary 5000 spectrophotometer equipped with an integrating sphere). The accessory also allowed for UV-Vis-NIR DR studies to be undertaken either in vacuum or in an oxygen atmosphere at significantly high temperatures (to 720 K) to assess dark chemical events occurring in photochromic titania with the participation of color centers. The DR spectral and kinetic measurements provided the opportunity to examine the separation of photoinduced charge carriers at traps and thermally stimulated carrier detrapping and recombination, as well as the response of color centers to oxidative/reductive treatments of photochromic TiO. Kinetic results also demonstrate the applicability of the fabricated DR accessory as a high-temperature reaction cell in the systematic study of the principal regularities in the formation and destruction of color centers in titania at various temperatures and gaseous atmospheres.

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Section: The Cryostat Accessorymentioning

confidence: 84%

In situ study of photo- and thermo-induced color centers in photochromic rutile TiO2 in the temperature range 90–720 K

Кузнецов

Glazkova

Mikhaylov

et al. 2016

Photochem Photobiol Sci

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“…No trace of moisture condensation was observed at the window at low temperatures, and no noticeable heating of the sphere occurred at temperatures up to 700 K under vacuum conditions. By comparison, Melsheimer et al [2] reported heating the integrating sphere in the Lambda 9 Perkin-Elmer spectrophotometer when carrying out DR measurements at high temper atures (673 K); the DR signal level relative to the reference beam in the accessory was 15%-20% (sample distance from the sphere: 12 mm), while the DR signal was 35%-45% when the sample was mounted 120 mm distant from the sphere.…”

Section: The Cryostat Accessorymentioning

confidence: 99%

Advanced diffuse reflectance spectroscopy for studies of photochromic/photoactive solids

Кузнецов

Glazkova

Mikhaylov

et al. 2019

J. Phys.: Condens. Matter

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The present article reports novel opportunities of diffuse reflectance (DR) spectroscopy extended through the use of a cryostat accessory for UV–vis–NIR spectrophotometers to investigate temperature dependences of DR spectra at the fundamental absorption edge of semiconductors at T = 90–600 K. Examined are rutile TiO2, a photochromic rutile TiO2 with strong absorption in the visible region, and the halide double perovskite Cs2AgBiBr6 that exhibited two optical band-to-band transitions in low-temperature DR spectra. Also reported are DR spectral and kinetics measurements of the separation of photogenerated charge carriers in various trap sites, their thermostimulated detrapping and their recombination in two different photochromic materials. The similarity between absorption and temperature-programmed annealing (TPA) spectra induced in the UV and Vis regions yielded physical evidence of the photo-formation of charge carriers upon Vis-light excitation of intrinsic defects (F-type centers) in yellow rutile TiO2. High-temperature oxidative/reductive treatments of samples, together with spectral and kinetics measurements were performed in situ with the accessory. Results led to assigning color centers in yellow TiO2 to Ti3+ centers as deep electron traps, and to the establishment of several types of Ti3+-based color centers that include extra-negatively charged Tiδ+ centers (3 > δ > 2). Photochromic occurrences are also elucidated in the Bi-doped perovskite CsPbBr3 under illumination in the region of intrinsic absorption and annealing of photoinduced absorption at T = 200–400 K. These phenomena are described in terms of the photogeneration of charge carriers followed by their trapping, which yielded Bi-related electron color centers responsible for the photoinduced absorption and for the thermostimulated detrapping of photoholes that ultimately recombine with the trapped electrons. The establishment of photochromism in the perovskites may lead to a further understanding of photoinduced and dark reversible phenomena in halide perovskites and halide perovskite-based solar cells.

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“…(1) An integration sphere, which is capable of collecting >95% of the scattered light over a wide range of wavelengths (82,83). To minimize the light losses, the sphere is coated with a perfectly reflecting material such as MgO and BaSO 4 .…”

Section: In Situ Characterization Methodsmentioning

confidence: 99%

Catalyst Characterization—Heterogeneous

Stavitski

Beale

Weckhuysen

2010

Encyclopedia of Catalysis

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The study of catalysts under in‐situ conditions enables the catalyst scientist to identify and understand the important steps, e.g., the formation of important reaction intermediates and active sites, and stages in a catalyst?s lifetime, such as activation/deactivation. The development of characterization methods as well as the design and construction of appropriate in‐situ cells and reactor probes are inevitable in order to obtain such insight. Both spectroscopic and scattering techniques have been used in attempt to understand quantitative structure/composition‐activity/selectivity relationships in catalysis. Armed with such detailed knowledge about the catalyst, it is then possible for scientists to design, in a more rational way, new and efficient catalysts for sustainable production of bulk and fine chemicals as well as for the removal of harmful compounds in industrial catalytic processes. This chapter provides an overview of the in‐situ characterization techniques available for investigation of catalytic materials. The possibilities and limitations of the methods are discussed and illustrated with numerous case studies.

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Improved experimental setup for in situ UV-vis-NIR spectroscopy under catalytic conditions

Cited by 12 publications

References 19 publications

In situ study of photo- and thermo-induced color centers in photochromic rutile TiO2 in the temperature range 90–720 K

In situ study of photo- and thermo-induced color centers in photochromic rutile TiO2 in the temperature range 90–720 K

Advanced diffuse reflectance spectroscopy for studies of photochromic/photoactive solids

Catalyst Characterization—Heterogeneous

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