Faculty Publications
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Item 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.Item Novel Co-Ni-graphene composite electrodes for hydrogen production(Royal Society of Chemistry, 2015) Subramanya, B.; Ullal, Y.; Shenoy, S.U.; Bhat, D.; Hegde, A.C.Active, stable and cost-effective electrocatalysts are key to water splitting for hydrogen production through electrolysis. Herein, we report the facile preparation of highly porous Co-Ni-graphene (Co-Ni-G) composite electrodes by electrodeposition for electrocatalytic applications. The incorporation of graphene into the Co-Ni matrix enhances the catalyst's activity for the hydrogen evolution reaction (HER) in an alkaline solution. The best coating exhibits a maximum current density of -850 mA cm-2 at -1.6 V, which is approximately 4 times better than that of the binary Co-Ni alloy indicating higher activity for hydrogen production. The addition of graphene to an electrolyte bath results in a porous encapsulated bundle of alloy nano-particles within the graphene network which effectively increases the electrochemically active surface area. As indicated by XPS analysis results, on addition of graphene the Co(0) and Ni(0) content in the deposit increases and as a result both cobalt/cobalt oxide and nickel/nickel oxide sites are evenly distributed on the Co-Ni-G electrode surface which is responsible for increased HER activity. The Tafel slope analysis showed that the HER follows a Volmer-Tafel mechanism. The structure-property relationship of the Co-Ni-G composite coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © The Royal Society of Chemistry 2015.Item Novel Fe-Ni-Graphene composite electrode for hydrogen production(Elsevier Ltd, 2015) Badrayyana, S.; Bhat, D.K.; Shenoy, U.S.; Ullal, Y.; Hegde, A.We have developed a novel, efficient and economical composite electrode for hydrogen production. The electrode has been formed by embedding graphene in the Fe-Ni matrix via room temperature electrodeposition. The obtained active coatings have been tested for their efficiency and performance as electrode surfaces for hydrogen evolution reaction (HER) in 6 M KOH by cyclic voltammetry and chronopotentiometry techniques. The coating obtained at 60 mA cm-2 exhibited approximately 3 times higher activity for hydrogen production than that of binary Fe-Ni alloy. Addition of graphene to electrolyte bath resulted in porous 3D projections of nano-sized spheres of Fe-Ni on the surface of graphene, which effectively increased the electrochemically active surface area. XPS analysis results showed the equal distribution of both Ni metal and NiO active sites on the composite. The addition of graphene favoured the deposition of metallic nickel, which accelerated the rate determining proton discharge reaction. All these factors remarkably enhanced the HER activity of Fe-Ni-Graphene (Fe-Ni-G) composite electrode. The Tafel slope analysis showed that the HER follows Volmer-Tafel mechanism. The structure-property relationship of Fe-Ni-G coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Modification of Ni-P alloy coatings for better hydrogen production by electrochemical dissolution and TiO2 nanoparticles(Royal Society of Chemistry, 2016) Elias, L.; Hegde, A.This work reports the modification of Ni-P alloy coatings for better hydrogen production by electrochemical dissolution and TiO2 nanoparticle incorporation. The first part is devoted to optimization of a new citrate bath for the development of an efficient electroactive Ni-P electrode material by electrodeposition, using glycerol as an additive. The Ni-P alloys developed at 4.0 A dm-2 and 2.0 A dm-2 were found to be good for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively as demonstrated by cyclic voltammetry (CV) and chronopotentiometry (CP) methods. The Ni-P alloy showing good catalytic activity for HER is found to be less active for OER and vice versa. The unique electrocatalytic property of the coatings was attributed to its structure, morphology and composition, confirmed by XRD, SEM and EDS analyses. In the second part, the electrocatalytic activity of Ni-P alloy coatings for HER has been improved further by anodic dissolution and TiO2 nanoparticle incorporation. Drastic improvement in the electrocatalytic activity for HER was found in both anodically treated and Ni-P-TiO2 composite coatings, compared to as-coated Ni-P alloys. The highest electrocatalytic character of the Ni-P-TiO2 composite coating was attributed to a greater number of electroactive centres, affected by TiO2 nanoparticle incorporation, and experimental results are discussed. © The Royal Society of Chemistry 2016.Item Cadmium sulfide nanostructures: Influence of morphology on the photocatalytic degradation of erioglaucine and hydrogen generation(Elsevier B.V., 2019) Shenoy, S.; Jang, E.; Park, T.J.; Gopinath, C.S.; Sridharan, K.Size and shape of inorganic materials are known to have great effects on their physical and chemical properties. Here, for the first time we report the visible light driven photocatalytic degradation of erioglaucine – a stable organic dye molecule in the presence of chemically synthesized nanoscale CdS with 1D (nanorods), 2D (nanosheets) and 3D (hierarchical) morphology. Visible light driven photocatalytic degradation efficiency of both 1D and 3D CdS in the removal of erioglaucine are identical. Surprisingly, with 5 min of sonication, the highly crystalline 3D CdS stacked with many thin nanowires containing numerous active surface sites exhibited four-fold enhanced photodegradation efficiency in comparison to 1D and 2D CdS. Scavenger studies revealed that electrons and superoxide radicals are primary reactive species involved in the photodegradation of erioglaucine, while cyclic photodegradation studies revealed the good stability of 3D CdS against photocorrosion. Further, the photocatalytic hydrogen evolution studies also revealed the excellent activity of 3D CdS in comparison to 1D and 2D CdS. Thus, we find that the morphology indeed influences the photocatalytic activity. These results reveal that 3D CdS nanostructures investigated in the present work are efficient photocatalysts that could be fine-tuned for both environmental remediation and hydrogen generation applications. © 2019 Elsevier B.V.Item Sol-gel electrospun ZnMn2O4 nanofibers as bifunctional electrocatalysts for hydrogen and oxygen evolution reactions(Institute of Physics Publishing helen.craven@iop.org, 2019) Shamitha, C.; Shetty, A.R.; Hegde, A.C.; Anandhan, S.Electrochemical water-splitting has gained significant attention for the development of next generation fuels. The present work is an investigation on the electrocatalytic activity towards both Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER) of ZnMn2O4 (ZMO) nanofabrics synthesized by sol-gel electrospinning followed by calcination (at 500, 600 and 700 °C). Poly(styrene-co-acrylonitrile) was used as the polymeric binder for the production of nanofabrics. The morphological features of ZMO nanofabrics were studied by scanning electron microscopy and field emission scanning electron microscopy. The electrocatalytic behavior of ZMO nanofabrics obtained at different calcination temperatures was evaluated using chrono-potentiometry, cyclic voltammetry, and linear sweep voltammetry in an alkaline medium (1 M KOH). The ZMO nanofabrics calcined at 500 °C exhibited the maximum electrocatalytic activity towards HER. This can be ascribed to their superior specific surface area (79.5 m2 g-1). The nanofabrics calcined at 700 °C displayed the least potential for O2 evolution and hence they are considered to be effective for OER. The results prove that ZMO nanofabrics are promising candidates as bifunctional electrocatalysts for water-splitting applications. © 2019 IOP Publishing Ltd.Item 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. © 2021Item Effect of annealing temperature on the bifunctional electrocatalytic properties of strontium nickelate (SrNiO3) nanoparticles for efficient overall water splitting(Elsevier Ltd, 2022) J, J.; Jayalakshmi, J.; Rodney, J.D.The global trend in energy demand has paved way for clean hydrogen (H2) energy production at large scale. To address this issue, perovskite (ABX3) nanomaterials are widely researched to replace the noble metal electrocatalysts for electrochemical water splitting. In this work, the effect of annealing temperature on the structural and electrochemical properties of combustion derived strontium nickelate (SrNiO3) nanoparticles are studied. Benefitting from the unique features of perovskites, SrNiO3 nanoparticles displays excellent OER and HER activity in 1.0 M KOH with an overpotential of 259 mV and 451 mV to achieve 10 mAcm−2 respectively. SrNiO3 nanoparticles show superior HER activity when annealed at higher temperature and subtle change in OER activity. The stability of SrNiO3 nanoparticles were noteworthy as it shows no degradation even after 12 h. The overall water splitting of highly active SrNiO3 nanoparticles was carried out in a two-electrode system and the setup posted a cell voltage of 1.88 V at 10 mAcm−2 after continuous water splitting for 24 h. Thus, SrNiO3 nanoparticles may possibly serve as a potential bifunctional electrocatalyst for H2 production. © 2022 Hydrogen Energy Publications LLCItem Numerical modeling of rice husk gasification in fluidized bed gasifier for sustainable biofuel production(Elsevier Ltd, 2022) Manu, J.; Madav, V.Currently, there is a growing interest in various alternative energy sources due to the global energy scenario and rising crude oil prices. Renewable sources of energy like biomass can be exploited to produce energy-rich syngas. The biomass gasification process converts energy-rich solid fuel into syngas by partial combustion. In the present study, rice husk gasification using steam and, a mixture of steam and CO2at temperatures ranging from 650°C to 750 °C and steam to biomass ratio of 0.5-2 is studied. Steam gasification enhances hydrogen production, and mixing with CO2helps optimizing the H2/CO ratio. The study uses the Euler-Euler method in combination with kinetic theory granular of flow which is modeled using the computational fluid dynamics approach implementing user-defined functions for heterogeneous char reactions. The increased particle diameter harms the gasification performance due to the lower heating value of the syngas. As the steam to biomass ratio is increased, there is a positive effect on syngas quality, while temperature has a negative effect. The addition of CO2increases the CO conversion in the syngas. The heterogeneous reaction rate vanishes close to zero after a height of 0.4 m, where all solid carbon is consumed. © 2022 American Society of Civil Engineers (ASCE). All rights reserved.Item Boosting overall electrochemical water splitting via rare earth doped cupric oxide nanoparticles obtained by co-precipitation technique(Elsevier Ltd, 2022) Rodney, J.D.; Deepapriya, S.; Jerome das, S.J.; Robinson, M.C.; Perumal, S.; Sadhana, S.; Periyasamy, P.; Jung, H.; Justin Raj, C.J.The development of electrocatalyst based on nonprecious metals has been a persistent issue as electrochemical water splitting requires electrocatalyst with advanced activity and stability. Further, the electrocatalyst must require low overpotential above the standard potential (>1.23 V) of water splitting to produce hydrogen. This study presents the facile co-precipitation derived rare earth dysprosium (Dy) doped cupric oxide nanoparticles (Cu1−xDyxO) as a non-noble transition metal oxide nanoparticle. The 3 % Dy doped CuO (3 % Dy/CuO) and 1 % Dy doped CuO (1 % Dy/CuO) electrocatalysts showed excellent Oxygen Evolution Reaction (OER) at 1.55 V vs RHE and Hydrogen Evolution Reaction (HER) at − 0.036 V vs RHE in aqueous 1 M KOH aqueous electrolyte to attain the benchmark current density (10 mA cm−2). The stability of the driven electrocatalyst in a bi-functional electrocatalytic setup was monitored for 24 h and was found to be exhibiting a cell voltage of about 2.1 V at 30 mA cm−2 constant current density. Further, the retention capability of the electrode was observed to be 99 % with a very minimal loss. This study hugely suggests the promising consequence of doping rare earth onto a non-precious metal oxide-based electrocatalyst, making it a highly effective bifunctional material for water splitting. © 2022 Elsevier B.V.