Noble metal-free dual cocatalysts for improved H₂ production from water splitting under solar irradiation

Anil Kumar Reddy Police(Police Anil Kumar Reddy),Sungjun Bae(배성준) 대한환경공학회 2022 대한환경공학회 학술발표논문집 Vol.2022 No.11

Eco-friendly, hydrogen fluoride-free, morphology-oriented synthesis of TiO₂ with exposed (001) facets

Police, Anil Kumar Reddy,Vattikuti, S.V. Prabhakar,Baik, Young-Jin,Chan, Byon Elsevier 2019 Ceramics international Vol.45 No.2

<P><B>Abstract</B></P> <P>Owing to its excellent properties, TiO<SUB>2</SUB> is considered as a wonder material and has been studied extensively in various fields of research. Furthermore, because of its morphology-oriented properties, anatase TiO<SUB>2</SUB> synthesized with controllable morphology and exposed (001) facets has been a subject of interest in recent times. In this perspective, herein, we report the controlled synthesis of anatase TiO<SUB>2</SUB> with different morphologies by an eco-friendly method. Samples of anatase TiO<SUB>2</SUB> with various morphologies were prepared with sodium titanates and urea as the starting materials under a one-pot hydrothermal method. Their morphologies were simply controlled by varying the concentration of urea in the aqueous solutions. From the FESEM and TEM images, changes in the morphologies, such as the presence of rods, rhombohedral, square bi-pyramidal, and truncated square bi-pyramidal structures, were observed. The growth mechanism of different morphologies of TiO<SUB>2</SUB> was established by considering the changes in the FTIR, Raman and TG-DTA patterns of the samples. These studies confirmed that the ammonium and carbonate ions formed during the hydrothermal conditions adsorbed on some crystal planes and hindered the growth of that plane, which resulted in TiO<SUB>2</SUB> with various morphologies. The UV–Vis DRS of the prepared samples showed intense absorption with a band gap of 3.2 eV, which confirmed the optical properties of TiO<SUB>2</SUB>. The photocatalytic activity of the as-synthesized samples was tested through methylene blue degradation. Optimum activity was seen for the TiO<SUB>2</SUB> with a truncated square bi-pyramidal morphology. The highly reactive exposed (001) facets of the truncated square bi-pyramidal morphology were responsible for the enhanced photocatalytic activity.</P>

Enhanced hydrogen production activity over BiO X TiO 2 under solar irradiation: Improved charge transfer through bismuth oxide clusters

Reddy, Police Anil Kumar,Manvitha, Chennaiahgari,Reddy, Pullagurala Venkata Laxma,Kim, Ki-Hyun,Kumari, Valluri Durga Elsevier Inc 2017 Journal of Energy Chemistry Vol.26 No.3

<P>A series of titania nanoparticles and nanotubes deposited with various quantities of bismuth (Bi) were prepared via sol-gel and hydrothermal methods, respectively. They were then characterized using X-ray diffraction spectroscopy (XRD), X-ray photo electron spectroscopy (XPS), UV-Vis diffused reflectance spectra (DRS), photoluminescence spectra (PLS), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), and BET surface analysis. These catalysts were employed for the photocatalytic production of hydrogen from a mixture of pure water and glycerol under solar light irradiation. The presence of the Bi(3 + x)+ species was found to play a vital role in enhancing activity while minimizing electron hole recombination (relative to bare TiO2). The nanotubes exhibited better activity than the nanoparticles of Bi-deposited TiO2, showing the significance of the morphology; however, photocatalytic activity is predominantly dependent on the deposition of bismuth. The activity increased by approximately an order of magnitude at the optimum concentration of Bi deposited over TiO2 (2 wt%). The presence of the Bi(3 + x)+ species played a vital role in minimizing electron hole recombination, resulting in higher activity compared to bare TiO2. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.</P>

Bismuth oxide cocatalyst and copper oxide sensitizer in Cu₂O/TiO₂/Bi₂O₃ ternary photocatalyst for efficient hydrogen production under solar light irradiation

Police, Anil Kumar Reddy,Vattikuti, S.V. Prabhakar,Mandari, Kotesh Kumar,Chennaiahgari, Manvitha,M.V., Phanikrishna Sharma,Valluri, Durga Kumari,Byon, Chan Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.10

<P><B>Abstract</B></P> <P>A novel Cu<SUB>2</SUB>O/TiO<SUB>2</SUB>/Bi<SUB>2</SUB>O<SUB>3</SUB> ternary nanocomposite was prepared, in which copper oxide improves the visible light absorption of TiO<SUB>2</SUB> and bismuth oxide improves electron–hole separation. The ternary composite exhibited extended absorption in the visible region, as determined by UV–Vis diffuse reflectance spectroscopy. High-resolution transmission electron microscopy images showed close contact among the individual semiconductor oxides in the ternary Cu<SUB>2</SUB>O/TiO<SUB>2</SUB>/Bi<SUB>2</SUB>O<SUB>3</SUB> nanocomposite. Improved charge carrier separation and transport were observed in the Cu<SUB>2</SUB>O/TiO<SUB>2</SUB>/Bi<SUB>2</SUB>O<SUB>3</SUB> ternary composite using electrochemical impedance spectroscopy and photocurrent analysis. TiO<SUB>2</SUB> modified with bismuth and copper oxides showed exceptional photocatalytic activity for hydrogen production under natural solar light. With optimum bismuth and copper oxide loadings, the Cu<SUB>2</SUB>O/TiO<SUB>2</SUB>/Bi<SUB>2</SUB>O<SUB>3</SUB> ternary nanocomposite exhibited an H<SUB>2</SUB> production (3678 μmol/h) 35 times higher than that of bare TiO<SUB>2</SUB> (105 μmol/h). The synergistic effect of improved visible absorption and minimal recombination was responsible for the enhanced performance of the as-synthesized ternary nanocomposite.</P>

Single-step hydrothermal synthesis of wrinkled graphene wrapped TiO₂ nanotubes for photocatalytic hydrogen production and supercapacitor applications

Police, Anil Kumar Reddy,Chennaiahgari, Manvitha,Boddula, Rajender,Vattikuti, S.V. Prabhakar,Mandari, Kotesh Kumar,Chan, Byon Elsevier 2018 Materials research bulletin Vol.98 No.-

<P><B>Abstract</B></P> <P>Herein, we discuss the synthesis of reduced graphene oxide and TiO<SUB>2</SUB> (rGO-TiO<SUB>2</SUB>) nanocomposites with varying ratios of rGO to TiO<SUB>2</SUB> by hydrothermal method. Photocatalytic ability of the nanocomposites was assessed for H<SUB>2</SUB> production under natural sunlight. At 5wt% GO loading, the rGO-TiO<SUB>2</SUB> exhibited 24,880μmol/g/h H<SUB>2</SUB>, 12.9 times to commercial P25-TiO<SUB>2</SUB> (1920μmol/g/h). The symmetric supercapacitor device fabricated using rGO-TiO<SUB>2</SUB> demonstrated 160F/g specific capacitance with 99% retention. The efficient charge carrier separation and transportation between TiO<SUB>2</SUB> nanotubes and rGO resulted high photocatalytic activity. The synergistic double layer pseudo capacitor behavior of rGO-TiO<SUB>2</SUB> is the reason for improved specific capacitance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wrinkle rGO wrapped TiO<SUB>2</SUB> nanotubes were prepared by alkanine hydrothermal method. </LI> <LI> Improved visible absorption and reduced recombination was witnessed in rGO-TiO<SUB>2</SUB>. </LI> <LI> H<SUB>2</SUB> production of 24,880μmole/g/h was achieved by rGO-TiO<SUB>2</SUB>, 12.9 folds to P25 TiO<SUB>2</SUB>. </LI> <LI> Double layer and pseudo capacitance of rGO-TiO<SUB>2</SUB> showed specific capacitance 160F/g. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Natural Zeolite Supported Ni/fe Bimetal Catalyst For Enhanced Dechlorination Of Trichloroethylene

POLICE ANIL KUMAR REDDY,Sungjun Bae(배성준),Minhee Choi(최민희),Sunho Yoon(윤선호),Jaehwan Shin(신재관),Kangmin Jeon(전강민) 대한환경공학회 2021 대한환경공학회 학술발표논문집 Vol.2021 No.11

TiO₂-based photocatalytic disinfection of microbes in aqueous media: A review

Laxma Reddy, P.Venkata,Kavitha, Beluri,Kumar Reddy, Police Anil,Kim, Ki-Hyun Academic Press 2017 Environmental research Vol.154 No.-

<P><B>Abstract</B></P> <P>The TiO<SUB>2</SUB> based photocatalyst has great potential for the disinfection/inactivation of harmful pathogens (such as <I>E.coli</I> in aqueous media) along with its well-known usefulness on various chemical pollutants. The disinfection property of TiO<SUB>2</SUB> is primarily attributed to surface generation of reactive oxygen species (ROS) as well as free metal ions formation. Furthermore, its disinfection capacity and overall performance can be significantly improved through modifications of the TiO<SUB>2</SUB> material. In this review, we provide a brief survey on the effect of various TiO<SUB>2</SUB> materials in the disinfection of a wide range of environmentally harmful microbial pathogens (<I>e.g</I>., bacteria, fungi, algae, and viruses) in aqueous media. The influencing factors (such as reactor design, water chemistry, and TiO<SUB>2</SUB> modifications) of such processes are discussed along with the mechanisms of such disinfection. It is believed that the combined application of disinfection and decontamination will greatly enhance the utilization of TiO<SUB>2</SUB> photocatalyst as a potential alternative to conventional methods of water purification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The advent of industrialization jeopardized the quality of drinking water. </LI> <LI> TiO<SUB>2</SUB> photocatalysis holds promise both in the degradation of pollutants and for disinfection. </LI> <LI> The applicability of TiO<SUB>2</SUB>-based decontamination is explored for microbial disinfection. </LI> <LI> Here we provide a comprehensive review on titania-based photocatalysts for disinfection. </LI> </UL> </P>

Rare earth metal Gd influenced defect sites in N doped TiO₂: Defect mediated improved charge transfer for enhanced photocatalytic hydrogen production

Mandari, Kotesh Kumar,Police, Anil Kumar Reddy,Do, Jeong Yeon,Kang, Misook,Byon, Chan Elsevier 2018 International journal of hydrogen energy Vol.43 No.4

<P><B>Abstract</B></P> <P>In this experimental studies, we report the synthesis of TiO<SUB>2</SUB> co-doped by both cationic and anionic sites by simple sol-gel based method. All the prepared samples exhibit the anatase crystalline morphology however, showed lattice distortion caused by the displacement of Ti<SUP>4+</SUP> sites by Gd<SUP>3+</SUP>. The improved visible absorption is witnessed by the Gd and N co-doping with an assured redshift in the absorption edge. The N and Gd displacement inside TiO<SUB>2</SUB> lattice accompanied by the creation of OTiN and GdOTi bonds are characterized by the X-ray photoelectron spectra. The strong resonance signal by Gd4<I>f</I> electrons in the electron paramagnetic resonance spectroscopy further substantiate the displacement of lattice cites of TiO<SUB>2</SUB> by Gd<SUP>3+</SUP> ions. The longevity of the photo produced charges observed in fluorescence spectra of Gd and N co-doped TiO<SUB>2</SUB> is because of the effective transfer of charges to the defect sites. The aforementioned catalysts are tested for their capacity for the H<SUB>2</SUB> production from water splitting. The 2 wt% gadolinium and nitrogen co-doped TiO<SUB>2</SUB> has shown 10764 μmol g<SUP>−1</SUP> H<SUB>2</SUB> production which is 26 times higher than the commercial Degussa P-25 catalyst. The enhanced activity for hydrogen production can be attributed to factors such as increased absorptivity under visible light and effective charge carrier separation.</P> <P><B>Graphical abstract</B></P> <P>Schematic representation of excitations in N-doped TiO<SUB>2</SUB>, Gd-doped TiO<SUB>2</SUB> and Gd, N co-doped TiO<SUB>2</SUB>.</P> <P>[DISPLAY OMISSION]</P>

Solar light response with noble metal-free highly active copper(II) phosphate/titanium dioxide nanoparticle/copper(II) oxide nanocomposites for photocatalytic hydrogen production

Mandari, Kotesh Kumar,Do, Jeong Yeon,Vattikuti, S.V. Prabhakar,Police, Anil Kumar Reddy,Kang, Misook Elsevier 2018 Journal of alloys and compounds Vol.750 No.-

<P><B>Abstract</B></P> <P>A novel Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TiO<SUB>2</SUB> nanoparticle (TNP)/CuO nanocomposite with an excellent natural solar-light-driven photocatalytic H<SUB>2</SUB> production performance was synthesized using a sol-gel method. The 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalyst displayed a better photocatalytic H<SUB>2</SUB> production yield (59.5 mmolg<SUP>−1</SUP>; natural solar light; 151 times higher than that of TNP under the optimal conditions; catalyst dosage of 0.010 g and 5% aqueous glycerol concentration) than TNP, CuO/TNP, Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP, and various Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> loadings in the Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalysts. The improved photocatalytic H<SUB>2</SUB> yields could be attributed to a suppressed recombination of charge carriers, preferable visible absorption ability, crystallinity, strong interactions, and high surface areas of 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO, which were confirmed using X-ray diffraction, temperature programmed reduction, diffuse reflectance spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, Brunauer-Emmett-Teller surface area analysis, elemental mapping, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence, and photocurrent techniques. The 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalyst could also contribute to the enhanced photostability and recyclability towards the photocatalytic hydrogen production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO nanocomposites were prepared by sol-gel method. </LI> <LI> Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO shows enhanced visible absorption and inhibit the recombination. </LI> <LI> Strong interaction between Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> and/or CuO nanoclusters with TNP by H<SUB>2</SUB>-TPR. </LI> <LI> Synergetic effect of Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>, CuO and TNP displayed effective redox reactions. </LI> <LI> Optimum H<SUB>2</SUB> yields obtained 59.5 mmol g<SUP>−1</SUP>, 151 times toTNP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Natural solar light-driven preparation of plasmonic resonance-based alloy and core-shell catalyst for sustainable enhanced hydrogen production: Green approach and characterization

Mandari, Kotesh Kumar,Do, Jeong Yeon,Police, Anil Kumar Reddy,Kang, Misook Elsevier 2018 Applied Catalysis B Vol.231 No.-

<P><B>Abstract</B></P> <P>Plasmonic Co and/or Ag monometal and their combinations as bimetal alloy and core-shell nanoparticles were prepared under natural sun light, using aqueous glycerol (in-situ reducing agent) and TNP (stabilizer). The formation of bimetallic alloy and core-shell NPs, and their uniform dispersion on the surface of TNP were evidenced by different characterization techniques. Ultraviolet-visible diffuse reflectance spectroscopy evidenced the two distinct characteristic surface plasmon resonance (SPR) absorption bands for the core-shell nanoparticles and a single distinct characteristic SPR band for the alloy. X-ray photoelectron spectroscopy revealed the presence of Ag and Co in the metallic form. The results of H<SUB>2</SUB>-temperature programmed reduction of fresh and used samples emphasized the characteristic reduction peaks for the reduction of monometal/bimetal oxide to metallic/bimetallic particles. The interaction of the loaded bimetallic particles with TNP resulted in a shift in the Raman bands. The photoluminescence spectra of the used samples revealed the formation of bimetallic alloy and core-shell structures, which resulted in a decrease in the recombination of charge carriers. X-ray diffraction, electron paramagnetic resonance spectroscopy, high-resolution transmission electron microscopy, and cyclic voltammetry analyses substantiated the same. The monometal-loaded photocatalysts and the bimetal alloy and core-shell nanoparticle-loaded photocatalysts were further examined for H<SUB>2</SUB> production with pure water/aqueous glycerol/crude glycerol under natural solar light irradiation. The (Ag-Co)<SUB>coloaded</SUB>TNP catalyst yielded the maximum H<SUB>2</SUB> evolution rate of 63 mmol g<SUP>−1</SUP>. For comparison, experiments were conducted under artificial solar light irradiation with similar experimental conditions. Based on the results, different mechanistic paths for insitu photoreduced Ag-Co bimetallic alloy and core-shell nanoparticles on TNP for H<SUB>2</SUB> production are envisaged.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Co/Ag bimetal alloy and core-shell are synthesized by in-situ photoreduction. </LI> <LI> Ag<SUB>core</SUB>@Co<SUB>shell</SUB> loaded TiO<SUB>2</SUB> exhibited enhanced H<SUB>2</SUB> production under sun light. </LI> <LI> Different aqueous scavengers are tested for H<SUB>2</SUB> production under solar light. </LI> <LI> Alloy and core-shell NPs act as electron sink and efficiently suppress the recombination. </LI> <LI> The formation mechanism of bimetal alloy and core-shell structures were discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>