Browsing by Author "Colmenares, J.C."

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Black titania: Turning the surface chemistry toward visible-light absorption, (photo) remediation of hazardous organics and H2 production
(Elsevier, 2022) Prekodravac, J.; Giannakoudakis, D.A.; Colmenares, J.C.; Nair, N.; Vasiljević, B.; Kepić, D.
Environmental protection and energy conversion by state-of-the-art photocatalysts emerge as imperative in pursuit for ideal, sustainable, and green oriented solutions. However, major drawbacks in broader application of one of the most promising semiconductor photocatalyst, titanium dioxide (TiO2), lie in the need for enhancing visible-light absorption and elevating the photocatalytic reactivity. Toward these directions, narrowing the material band gap and functionalization of the surface chemistry are among the most prosperous materials design approaches. As reported in earlier work, the surface structure engineering proved to be an encouraging approach to endow optical and electrical properties of the TiO2-based material. For the first time, the black powder of TiO2 with a disordered lattice and hydrogen surface doping was obtained through hydrogenation under high pressure and temperature, consequently leading to narrowing the optical band gap to 1.54eV. The presented chapter aims to reveal in-depth all the literature available information related to the black titania synthesis in addition of sharing in details its prosperous physicochemical properties. Feature information related to the photocatalytic activity of black TiO2 as well as of the most crucial features will also be provided. Finally, the chapter will conclude with the derived significant benefits of such material properties in photocatalytic treatment of organic pollutants and hydrogen production. © 2023 Elsevier Inc. All rights reserved.
Design and development of TiO2 coated microflow reactor for photocatalytic partial oxidation of benzyl alcohol
(Elsevier B.V., 2020) Pradhan, S.R.; Nair, V.; Giannakoudakis, D.A.; Lisovytskiy, D.; Colmenares, J.C.
The synthesis of valuable organic compounds from naturally available and renewable biomass is an open field of research towards adaptation in real-life applications. Photocatalytic valorization is assumed as a potential candidate, although the lower efficiency of the traditional batch photocatalytic reactor sets some drawbacks. Recently, photocatalytic microreactors revealed as a prosperous candidate for various photocatalytic reactions, especially for selective oxidation. This area of research is challenging due to the development of the proper photocatalytic microreactor for the targeted application. Deposition of the catalyst on the internal surface of the microreactor, the sufficient utilization of the irradiation, optimization of the reaction parameters are among the most vital parameters that should be considered upon the design. Although, to obtain the most active material and tune its crucial features to maximize its catalytic performance inside the microreactors is the uppermost important part. This work introduces ultrasound-assisted TiO2 deposition on the inner walls of a perfluoroalkoxyalkane microtube under mild conditions. The deposition experiments were carried out with commercial and sol-gel synthesized TiO2. The materials were characterized by XRD, UV–vis DRS, Scanning Electron Microscopy (SEM), and nitrogen sorption. The photocatalytic activities of the TiO2 nano-engineered fluoropolymer based microreactors were evaluated for the oxidation of benzyl alcohol in flow. © 2020 The Author(s)
Homogeneous photocatalysts immobilized on polymeric supports: Environmental and chemical synthesis applications
(Elsevier, 2021) Prekodravac, J.; Nair, V.; Giannakoudakis, D.A.; Hsu, S.H.-Y.; Colmenares, J.C.
The interest in homogeneous photocatalysis arises from the high activity and selectivity advantages of controlled photochemical transformations such as synthesis of chemical/pharmaceutical products or complete degradation/mineralization of hazardous compounds. However, the major drawback of homogeneous photocatalytic reactions lies in the separation and recovery of the photocatalyst after the reaction, necessary to make the photocatalytic process eco-friendly. Immobilization of homogeneous photocatalysts on different supports is considered to be a viable method to increase the retainability and reusability of the photocatalyst simultaneously. This chapter aims to provide an in-depth information related to the immobilization of various homogeneous photocatalysts on well-known synthetic and natural polymers. Detailed information related to the potential environmental and chemical synthesis applications of immobilized homogeneous photocatalysts are also discussed. Finally, this chapter concludes with a new direction in emerging technologies for developing better supported photocatalysts. © 2021 Elsevier Inc. All rights reserved.
Metal organic frameworks as desulfurization adsorbents of DBT and 4,6-DMDBT from fuels
(MDPI AG indexing@mdpi.com Postfach Basel CH-4005, 2019) Kampouraki, Z.-C.; Giannakoudakis, D.A.; Nair, V.; Hosseini-Bandegharaei, A.; Colmenares, J.C.; Deliyanni, E.A.
Ultradeep desulfurization of fuels is a method of enormous demand due to the generation of harmful compounds during the burning of sulfur-containing fuels, which are a major source of environmental pollution. Among the various desulfurization methods in application, adsorptive desulfurization (ADS) has low energy demand and is feasible to be employed at ambient conditions without the addition of chemicals. The most crucial factor for ADS application is the selection of the adsorbent, and, currently, a new family of porous materials, metal organic frameworks (MOFs), has proved to be very effective towards this direction. In the current review, applications of MOFs and their functionalized composites for ADS are presented and discussed, as well as the main desulfurization mechanisms reported for the removal of thiophenic compounds by various frameworks. Prospective methods regarding the further improvement of MOF’s desulfurization capability are also suggested. © 2019 MDPI AG. All rights reserved.
Metal organic frameworks as desulfurization adsorbents of DBT and 4,6-DMDBT from fuels
(MDPI AG indexing@mdpi.com Postfach Basel CH-4005, 2019) Kampouraki, Z.-C.; Giannakoudakis, D.A.; Nair, V.; Hosseini-Bandegharaei, A.; Colmenares, J.C.; Deliyanni, E.A.
Ultradeep desulfurization of fuels is a method of enormous demand due to the generation of harmful compounds during the burning of sulfur-containing fuels, which are a major source of environmental pollution. Among the various desulfurization methods in application, adsorptive desulfurization (ADS) has low energy demand and is feasible to be employed at ambient conditions without the addition of chemicals. The most crucial factor for ADS application is the selection of the adsorbent, and, currently, a new family of porous materials, metal organic frameworks (MOFs), has proved to be very effective towards this direction. In the current review, applications of MOFs and their functionalized composites for ADS are presented and discussed, as well as the main desulfurization mechanisms reported for the removal of thiophenic compounds by various frameworks. Prospective methods regarding the further improvement of MOFâ€™s desulfurization capability are also suggested. Â© 2019 MDPI AG. All rights reserved.
Role of catalyst supports in biocatalysis
(John Wiley and Sons Ltd, 2023) Manikandan, S.K.; Giannakoudakis, D.A.; Prekodravac, J.R.; Nair, V.; Colmenares, J.C.
Biocatalysis utilizes enzymes and microbial cells as catalysts for a wide range of applications in biotechnology. Immobilization of biocatalysts on various materials has several advantages, including the capacity for reuse, quick reaction termination, easy biocatalyst recovery and operational stability. The present article focuses on the use of material supports for developing immobilized biocatalysts in applications related to energy, environment and chemical synthesis. The work provides a comprehensive overview of a broad class of materials, including organic, inorganic and composites, that have been shown to be prosperous candidates to support the immobilization of enzymes and microbial cells. It also highlights the properties of nanomaterial support such as large surface area and comfort compartment for immobilization. The availability of different types of materials as catalyst support provides an opportunity to understand and develop efficient biocatalytic systems. The choice of selecting a catalyst support will mostly depend on the interaction of the material with the enzyme or microbial cell. Finally, potential challenges, future approaches in developing immobilized biocatalytic systems for various applications and novel material supports are suggested. Â© 2022 Society of Chemical Industry (SCI). Â© 2022 Society of Chemical Industry (SCI).
Role of catalyst supports in biocatalysis
(John Wiley and Sons Ltd, 2023) Manikandan, S.K.; Giannakoudakis, D.A.; Prekodravac, J.R.; Nair, V.; Colmenares, J.C.
Biocatalysis utilizes enzymes and microbial cells as catalysts for a wide range of applications in biotechnology. Immobilization of biocatalysts on various materials has several advantages, including the capacity for reuse, quick reaction termination, easy biocatalyst recovery and operational stability. The present article focuses on the use of material supports for developing immobilized biocatalysts in applications related to energy, environment and chemical synthesis. The work provides a comprehensive overview of a broad class of materials, including organic, inorganic and composites, that have been shown to be prosperous candidates to support the immobilization of enzymes and microbial cells. It also highlights the properties of nanomaterial support such as large surface area and comfort compartment for immobilization. The availability of different types of materials as catalyst support provides an opportunity to understand and develop efficient biocatalytic systems. The choice of selecting a catalyst support will mostly depend on the interaction of the material with the enzyme or microbial cell. Finally, potential challenges, future approaches in developing immobilized biocatalytic systems for various applications and novel material supports are suggested. © 2022 Society of Chemical Industry (SCI). © 2022 Society of Chemical Industry (SCI).
Ultrasound-assisted decoration of CuOx nanoclusters on TiO2 nanoparticles for additives free photocatalytic hydrogen production and biomass valorization by selective oxidation
(Elsevier B.V., 2021) Giannakoudakis, D.A.; Qayyum, A.; Nair, V.; Khan, A.; Pradhan, S.R.; Prekodravac, J.; Rekos, K.; LaGrow, A.P.; Bondarchuk, O.; ?omot, D.; Triantafyllidis, K.S.; Colmenares, J.C.
The herein presented ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic approach was followed in order to avoid the drawbacks of the conventional wet impregnation synthesis. The goal was to homogeneously decorate the surface of the TiO2 nanoparticles with nanometric sized (< 4 nm) clusters of mixed cupric and cuprous oxides. The physicochemical features of the nanocomposite (TiO2[sbnd]CuOx) were determined by high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and Diffuse reflectance (DR) spectroscopy. TiO2[sbnd]CuOx showed an enhanced and continuous capability to generate molecular hydrogen upon low power ultraviolet irradiation. The benchmark commercial TiO2 P25 did not reveal any H2 formation under these conditions. TiO2[sbnd]CuOx presented also a high efficiency for the additives-free selective partial oxidation of two well established biomass derived model platform chemicals/building blocks, 5-hydroxymethylfurfural (HMF) and benzyl alcohol (BnOH) to the value-added chemicals 2,5-diformylfuran (DFF) and benzyl aldehyde (PhCHO), respectively. The nanocomposite showed higher DFF and PhCHO yield compared to P25. © 2021