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>

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

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>

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>

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>

In situ fabrication of the Bi₂O₃–V₂O₅ hybrid embedded with graphitic carbon nitride nanosheets: Oxygen vacancies mediated enhanced visible-light–driven photocatalytic degradation of organic pollut

Vattikuti, S.V. Prabhakar,Police, Anil Kumar Reddy,Shim, Jaesool,Byon, Chan Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.447 No.-

<P><B>Abstract</B></P> <P>Novel mesoporous ternary hybrids comprising Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts anchored on graphitic carbon nitride (g-C<SUB>3</SUB>N<SUB>4</SUB>) nanosheets were synthesized via an in situ co-pyrolysis approach and characterized by a series of techniques, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis, Fourier transform infrared spectroscopy, ultraviolet–visible spectrometry, photoluminescence and electron paramagnetic resonance (EPR). The hybrids were subsequently tested as photocatalysts for the degradation of the phenol red (PR) pollutant under visible light irradiation. The well-designed ternary hybrids showed pure and randomly distributed Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> (denoted as BiV) nanoparticles on monodispersed g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets. The as-prepared ternary Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB>@g-C<SUB>3</SUB>N<SUB>4</SUB> (i.e., BiV@g-C<SUB>3</SUB>N<SUB>4</SUB>) hybrids demonstrated high specific surface areas with remarkable mesoporous characteristics. The photodegradation efficiencies of the ternary hybrids for PR were 1.2 and 1.8 times higher than those of binary BiV and pristine Bi<SUB>2</SUB>O<SUB>3</SUB>, respectively, at 50 min irradiation time under simulated solar light irradiation. At the end of the phototreatment, the amount of PR pollutant was reduced to 98.1% in 50 min by using the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposites under simulated solar light irradiation and more efficient for photocatalytic H<SUB>2</SUB> production. Based on an electrochemical analysis, we propose a photocatalytic degradation pathway for PR under visible light irradiation. In addition, the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposite photocatalysts exhibited both long-term stability and photocatalytic efficiency for the degradation of the PR dye. The excellent photoelectrochemical performance of the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalysts can be ascribed to their highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> and Bi<SUB>2</SUB>O<SUB>3</SUB> nanoparticles, mesoporous structure, and high specific surface area (83.75 m<SUP>2</SUP> g<SUP>−1</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst was successfully synthesized via co-pyrolysis. </LI> <LI> Synthetic procedure may open up an opportunity to tailor the morphologies of nanocomposites. </LI> <LI> Studied the oxygen vacancies enhanced photocatalytic activity of BiV@g-C<SUB>3</SUB>N<SUB>4.</SUB> </LI> <LI> Photodegradation and H<SUB>2</SUB> evolution mechanism of the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst is elucidated and discussed. </LI> <LI> BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst demonstrated 21.08 folds higher H<SUB>2</SUB> production rate than pure ones. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hydrothermally synthesized highly dispersed Na2Ti3O7 nanotubes and their photocatalytic degradation and H2 evolution activity under UV and simulated solar light irradiation

S. V. Prabhakar Vattikuti,Police Anil Kumar Reddy,Narendra Bandaru,심재술,Chan Byon 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.4

Photocatalytic water splitting technologies are currently being considered for alternative energy sources. However, the strong demand for a high H2 production rate will present conflicting requirements of excellent photoactivity and low-cost photocatalysts. The first alternative may be abundant nanostructured titanate-related materials as a photocatalyst. Here, we report highly dispersed Na2Ti3O7 nanotubes synthesized via a facile hydrothermal route for photocatalytic degradation of Rhodamine B (RhB) and the water splitting under UV-visible light irradiation. Compared with commercial TiO2, the nanostructured Na2Ti3O7 demonstrated excellent photodegradation and water splitting performance, thus addressing the need for low-cost photocatalysts. The as-synthesized Na2Ti3O7 nanotubes exhibited desirable photodegradation, and rate of H2 production was 1,755 mol·g1·h1 and 1,130 mol·g1·h1 under UV and simulated solar light irradiation, respectively; the resulting as-synthesized Na2Ti3O7 nanotubes are active in UV light than that of visible light response.

Hydrothermally synthesized Na₂Ti₃O₇ nanotube–V₂O₅ heterostructures with improved visible photocatalytic degradation and hydrogen evolution - Its photocorrosion suppression

Vattikuti, S.V. Prabhakar,Reddy, Police Anil Kumar,NagaJyothi, P.C.,Shim, Jaesool,Byon, Chan Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.740 No.-

<P><B>Abstract</B></P> <P>There is still a need to prepare heterostructure photocatalysts with high activity and recyclability but without using precious metals to reduce the cost of photocatalysts. Thus, a facile and simple method for the synthesis of a Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst via hydrothermal synthesis is reported herein. The chemical composition, morphology, and structural features of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N<SUB>2</SUB> adsorption–desorption specific surface area analysis (BET), and diffuse reflectance absorption (DRS) methods. It was observed that the specific surface area of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst increased with the incorporation of V<SUB>2</SUB>O<SUB>5</SUB>. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst was then used for the removal of rhodamine B (RhB) under simulated solar light irradiation. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst revealed excellent photocatalytic activity and photodegradation kinetics as compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. Furthermore, both the photoactivity and long-term stability of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst were superior to those of the pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. The excellent photocatalytic performance of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst can be ascribed to its high specific surface area (283.71 m<SUP>2</SUP>g<SUP>−1</SUP>), mesoporous structure, highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> nanoparticles, and hindrance of electron–hole pair recombination of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> due to the V<SUB>2</SUB>O<SUB>5</SUB> incorporation, which is proven by the photoelectrochemical results, including photocurrent and electron impendence spectroscopy results. In addition, during the study of photocatalytic hydrogen evolution, the hydrogen yield of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> nanocomposite was 1.83 times that of pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>, which also exhibited excellent photocatalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heterojunction of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs was developed via hydrothermal method. </LI> <LI> Visible photocatalytic RhB degradation studies were performed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> <LI> Improved degradation efficiency was observed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs when compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> NPs were successfully utilized as cocatalyst for pollutant degradation. </LI> <LI> Charge recombination was diminished in the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs by the addition of V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>