BITS Faculty Publications
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867
Browse
14 results
Search Results
Item Tin and lanthanum modified Ni/CeO2 catalyst systems for low temperature steam reforming of ethanol(Elsevier, 2024-01) Roy, BanasriThis work examines the Ni–Sn/Ce–La–O catalyst systems for low-temperature stream reforming of ethanol. Catalysts of 5 and 20 wt% metal loading, and different Ce:La ratios are prepared by ultra-sonication assisted solution combustion synthesis method. Catalysts at total metal loading 5 wt% with 33 and 67 at. % La and optimum Sn (Ni:Sn = 14:1) demonstrate better efficiency compared to the Ni/CeO2 catalysts. At 20 wt% metal loading and Ni:Sn = 1:1 atomic ratio, catalytic activity degrades. The best activity and stability are revealed for the N14S1(5)/CL21 catalyst with 5 wt.% total metal loading, Ni:Sn = 14:1, and Ce:La = 2:1 mol ratio. Physico-chemical characterizations (XRD, H2 -TPR, NH3-TPD, Raman, FESEM, TEM, XPS, N2 adsorption-desorption, DTA/TGA, etc.) are performed to understand the role of the metal loading, Sn, and La in the catalytic activity and coke deposition behavior.Item Synthesis of Highly Ordered TiO2 Nanorods on a Titanium Substrate Using an Optimized Hydrothermal Method(Springer, 2022-02) Sarkar, Bibhas R.; Hazra, ArnabIn this study, highly stable and well-oriented one-dimensional (1D) TiO2 nanorods were grown over a conductive titanium (Ti) substrate by optimizing various physical and chemical parameters involved in the hydrothermal method. Previous works have reported extensively on the synthesis of 1D TiO2 nanorods on fluorine-doped tin oxide-coated glass substrates using the hydrothermal method. However, glass substrates suffer from poor integration, compatibility, and stability issues when implemented in device applications. To overcome the challenges with glass substrates, in the current study, we propose an optimized hydrothermal route to synthesize highly ordered 1D TiO2 nanorods on a metal (Ti) substrate. The structural and morphological parameters of the nanostructures, including crystal phase, length, diameter, and density of nanorods, were studied with the help of field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction spectroscopy, and photoluminescence spectroscopy. The morphology of the nanostructures was varied by changing the chemical composition of the mother solution and physical parameters of time and temperature of the reactions involved during hydrothermal synthesis. It was shown that by optimizing the reaction parameters, multi-crystalline three-dimensional TiO2 nanoflowers could be transformed to single-crystalline 1D TiO2 nanorods. One-dimensional TiO2 nanorods on the Ti substrate were then implemented in a metal–insulator–metal (MIM) type of device (Au/TiO2 nanorods/Ti) and used for ethanol sensing. At 100°C, the sensor showed the maximum response magnitude of 61% towards 300 ppm of ethanol.Item Matrix-isolation FTIR spectroscopic study and quantum chemical calculations of 1:1 adduct of CHCl3 and C2H5OH in N2 matrix(Elsevier, 2024-06) Chakraborty, Amrita; Chakraborty, Shamik[Image 1-Image 2] mixture is a common binary solvent used in industries, organic synthesis, lipid extraction, drug extraction, etc. The purpose of this study is to have a molecular level understanding of the interaction of Image 1 with Image 2. The experiments have been carried out in low temperature Image 3 matrix using Fourier Transform Infrared spectroscopy. Electronic structure calculations have been performed to identify the possible binding motifs between Image 1 and Image 2. Three minima have been obtained on the dimer potential energy surface stabilised by Image 4 and Image 5 hydrogen bond, and Image 6 halogen bond interactions. Formation of more than one complexes have been confirmed using the experimental and simulated IR spectra. Energy decomposition analysis and Natural bond orbital analysis have been performed to understand the nature of interaction and the driving force for complexation. This is one of the first reports where separate complexes have been identified between Image 1 and anti and gauche conformers of Image 2 in the low temperature matrix.Item Study of preparation method and oxidization/reduction effect on the performance of nickel-cerium oxide catalysts for aqueous-phase reforming of ethanol(Elsevier, 2015-12) Roy, BanasriThe effect of preparation method and oxidation state of the active metal on the catalytic activity of Ni–Ce–O catalysts was studied for aqueous phase reforming of ethanol. A sol-gel (SG) route and a solution combustion synthesis (SCS) method were used for the preparation of 10 wt% Ni loaded catalysts. The catalytic activity of three groups of catalysts; reduced at 425 °C (HR, metallic Ni), reduced at 1000 °C (FR, metallic Ni), and not reduced (NR, as NiO) were tested at different operating conditions. The difference in the metal particle sizes, governed by the preparation method, affects the catalytic efficiency most, not the reduced or oxidized state of Ni. The SG samples were superior for ethanol conversion and selectivity for H2 and CO2 compared to the SCS samples. The X-ray photoelectron spectroscopy (XPS) analysis of the samples demonstrated that the relative ratio of Ce2O3 to CeO2 increased inside the reactor. While Ni doping increases oxygen mobility in the Ce–O lattice, Ce3+ converts Ni2+ to metallic Ni inside the reactor. This can explain why the reduction stage for Ni–Ce–O system in APR is irrelevant. Higher oxygen mobility through the support helps oxidation of CO to CO2 leading to improved catalytic performance.Item Low temperature steam reforming of ethanol over cobalt doped bismuth vanadate [Bi4(V0.90Co0.10)2O11-δ (BICOVOX)] catalysts for hydrogen production(Elsevier, 2021-01) Roy, BanasriThe atmospheric pressure low temperature steam reforming of ethanol over Bi4(V0.90Co0.10)2O11-δ (BICOVOX) catalysts, synthesize by a solution combustion synthesis method and calcined at 400, 600 and 800 °C, has been investigated at different reactor temperatures, H2O: EtOH molar ratios and feed flow rates. For fresh catalysts amount, crystallinity and particle size of pure γ-BICOVOX phase is observed to increase with increasing calcination temperature. Phase purity and crystallinity of the catalysts are almost retained till 30 h of activity study with some amount of carbon formation as derived from XRD, XPS, FESEM and simultaneous DTA-TGA study. Catalyst calcined at 600 °C (BICOVOX-600) exhibits the highest ethanol conversion (100%) with maximum H2 selectivity (80%) under reaction conditions of 400 °C, 23:1H2O: EtOH molar ratio and 0.35 cc min−1 feed flow rate. The maximum O2− vacancy present in lattice and lowest coke deposition could explain the best performance of BICOVOX-600 catalyst.Item Deactivation study of the BICOVOX catalysts used in low temperature steam reforming of ethanol for H2 production(Elsevier, 2021-10) Roy, BanasriThe γ-BICOVOX, having high O2- mobility at low temperature (≤300 °C), might be a good catalyst for hydrogen production by low temperature steam reforming (LTSR) of ethanol. LTSR (at atmospheric pressure) of ethanol over Bi4(V0.90Co0.10)2O11-δ (BICOVOX) catalysts (synthesized by a solution combustion method and calcined at 400, 600 and 800 °C) has been investigated at the reaction conditions of 400 °C, H2O: EtOH molar ratio 23:1 and 0.35 ml min−1 feed flow rate. Catalysts remain active for the time period of ~30 h and after that start to deactivate. According to the XRD analysis γ- BICOVOX decomposes to BiVO4, Bi2O3, and Bi phases due to a reducing environment present inside the reactor. According to the XPS analysis, decrease in γ- BICOVOX amount diminishes the oxygen vacancy in the lattice. This probably causes significant decline in O2- mobility through the lattice and consequently carbon deposition occurs (derived from XPS, FESEM & DTGA) leading to an almost complete deactivation of the catalysts within 150 h.Item Nanostructural evolution of hydrothermally grown SrTiO3 perovskite and its implementation in gaseous phase detection of ethanol(IOP, 2023-07) Ghosh, Sarbani; Hazra, ArnabA group of SrTiO3 nanostructures with unique nano-architecture have been synthesized in the current study. Sol–gel derived TiO2 nanoparticles along with Sr(OH)2 solution was processed with facial hydrothermal reaction at 180 °C and highly stable and distinct morphologies of SrTiO3 were developed after different reaction time. Nanobush, nanograss, nanorod and nanosphere morphologies were created after 10, 14, 18 and 24 h of hydrothermal reaction. SrTiO3 nanosphere was transformed into nano-hollow sphere morphology after thermal annealing at 600 °C. Detailed morphological, structural and chemical characterizations were carried out for all the distinct nanoforms of SrTiO3 where they exhibited high crystallinity, and chemical stability along with excellent surface properties like high porosity, roughness, and large effective surface area. Due to having rich surface properties, all the SrTiO3 morphologies were then implemented for gaseous phase detection of multiple volatile organic compounds (VOCs). However, all the SrTiO3 nanoforms showed ethanol selective behavior among all the VOCs. Nanograss and nano-hollow spheres exhibited excellent ethanol sensing with 69 and 78 response values (Rv/Ra) in 50 ppm ethanol at 150 °C with appreciably fast response/recovery times of 36 s/34 s and 150 s/ 58 s, respectively. Additionally, all the SrTiO3 nanostructures exhibited anti-humidity characteristics and potential sensing in humid ambient (up to 80% RH). Later, the ethanol selective behavior of SrTiO3 was established by density functional theory simulations which envisaged the highest negative adsorption energy and smallest distance (r) for ethanol molecule, implying stable adsorption with SrTiO3 (110) system.Item Ultrathin Films of TiO2 Nanoparticles at Interfaces(ACS, 2015-01) Gupta, Raj Kumar; Manjuladevi, V.; Hazra, ArnabThe properties of a material change remarkably as a result of the scaling dimensions. The Langmuir–Blodgett (LB) film deposition technique is known to offer precise control over the film thickness and the interparticle separation. To form a well-ordered LB film, it is essential to form a stable Langmuir film at the air–water interface. Here, we report our studies on ultrathin films of TiO2 nanoparticles at air–water and air–solid interfaces. The Langmuir film of TiO2 nanoparticles at the air–water interface was found to be very stable, and it exhibits loose-packing and close-packing phases. The LB films were transferred onto solid substrates for characterization and application. The surface morphology of the LB film was obtained by a field emission scanning electron microscope. The optical and electronic properties of the LB films of TiO2 nanoparticles were studied using UV–vis spectroscopy and current–voltage measurements, respectively. The LB film of TiO2 nanoparticles was employed for ethanol gas sensing, and the sensing performance was compared to that of bulk material. Because of the enormous gain in the surface to volume ratio and the increase in crystalline defect density in the ultrathin LB film of TiO2 nanoparticles, the LB film is found to be a potential functional layer for ethanol sensing as compared to the bulk material.Item Highly Repeatable Low-ppm Ethanol Sensing Characteristics of p-TiO2-Based Resistive Devices(IEEE, 2015-01) Hazra, ArnabIn this paper, we report on the development of a highly sensitive, relatively low-temperature ethanol sensor based on sol-gel derived p-TiO 2 thin film. The p-type anatase TiO 2 thin film was deposited by sol-gel technique on a thermally oxidized <;100> p-Si (resistivity 5 Ω cm) substrate. Anatase TiO 2 phase with <;101> nanocrystallinity was confirmed with an average particle size of ~11 nm from X-ray diffraction and field emission scanning electron microscopic study. Ethanol sensor study, in the resistive mode, was carried out at a relatively low operating temperature range (75 °C-175 °C) for sensing low concentrations of ethanol in air (5-100 ppm). Response magnitude of ~146% was observed at 150 °C toward 100-ppm ethanol (in air) with corresponding response time and recovery time of 39 and 15 s, respectively. The sensor showed appreciably high-response magnitude (129%) even at low ethanol concentration (5 ppm) with acceptable response and recovery time (54 and 22 s, respectively) at the same operating temperature (150 °C). At a particular temperature, for all the ethanol concentrations, sensor showed minimal base line resistance drift, thereby offering highly repeatable and stable sensing performance. Ethanol selectivity study against other volatile organic compounds, such as methanol, acetone, and 2-butanone, was also investigated and was found to be quite promising. Ethanol sensing mechanism for such p-type TiO 2 has also been discussed in the light of corresponding oxygen vacancy model.Item Electroless deposition of Pd/Pt nanoparticles on electrochemically grown TiO2 nanotubes for ppb level sensing of ethanol at room temperature(RSC, 2021) Hazra, ArnabThis work presents a comparative sensing study of three sensors based on pristine TiO2 nanotubes, Pd loaded TiO2 nanotubes, and Pt loaded TiO2 nanotubes. Pristine TiO2 nanotubes were synthesized using an electrochemical anodization method and an electroless plating method was used for the uniform deposition of noble metal nanoparticles of either Pd or Pt over the surface of TiO2 nanotubes. The samples were thoroughly characterized by XRD, FESEM, EDS, TEM, and XPS techniques. The sensitivity of all three sensors was investigated at room temperature (300 K) for different volatile organic compounds like ethanol, methanol, 2-propanol, acetone, and benzene. The results revealed that loading of Pd and Pt nanoparticles improved the response magnitude of the sensor remarkably as these noble metals possess better oxygen dissociation capability than pristine TiO2. The Pd–TiO2 nanotube sensor exhibited a maximum response magnitude of 20–98% towards 100–1000 ppb of ethanol at room temperature. Notably, the formation of Pd/Pt–TiO2 discrete heterojunctions on the surface of TiO2 nanotubes was found to be responsible for enhanced sensitivity of the sensors.