Unbiased Spontaneous Solar Fuel Production using Stable LaFeO3 Photoelectrode

This is the final version of the article. Available from Springer Nature via the DOI in this record.Photoelectrochemical (PEC) water splitting to produce solar fuel (hydrogen) has long been considered as the Holy Grail to a carbon-free hydrogen economy. The PEC concept to produce solar fuel is to emulate the natural photosynthesis using man made materials. The bottle-neck in realising the concept practically has been the difficulty in identifying stable low-cost semiconductors that meet the thermodynamic and kinetic criteria for photoelectrolysis. We have fabricated a novel p-type LaFeO3photoelectrode using an inexpensive and scalable spray pyrolysis method. Our nanostructured LaFeO3photoelectrode results in spontaneous hydrogen evolution from water without any external bias applied. Moreover, the photoelectrode has a faradaic efficiency of 30% and showed excellent stability over 21 hours. From optical and impedance data, the constructed band diagram showed that LaFeO3can straddle the water redox potential with the conduction band at -1.11 V above the reduction potential of hydrogen. We have fabricated a low cost LaFeO3photoelectrode that can spontaneously produce hydrogen from water using sunlight, making it a strong future candidate for renewable hydrogen generation.We acknowledge EPSRC-DTP for Ph D student ship to GSP. The financial support was provided by Engineering and Physical Science Research Council, UK (EPSRC) under the research grant No EP/P510956/1 and EP/R512801/1. We also acknowledge UKIERI-DST2016-17-0089 project for partly funding the present work. NSG Pilkington Glass Ltd. is acknowledged for kindly providing the FTO substrates for this work. The funders had no role in study design, data collection and analysis or preparation of the manuscript

Structural and electronic properties of oxygen defective and Se-doped p-type BiVO⁠4(001) thin film for the applications of photocatalysis

This is the final version. Available on open access from Elsevier via the DOI in this record.There is another record in ORE for this publication: http://hdl.handle.net/10871/36011Monoclinic BiVO4 is being used as a photocatalyst due to its stability, cost-effectiveness, ease of synthesis, and narrow band gap. Although, the valence band maximum, VBM (∼−6.80 eV vs vacuum) of BiVO4 is well below the redox potential of water but having less positive conduction band minimum, CBM (−4.56 eV vs vacuum), responsible for its low efficiency. We have carried out a comprehensive periodic density functional theory (DFT) simulations for the pristine, Oxygen defective (Ov) and Se doped BiVO4, to engineer not only its CB edge position but the overall photocatalytic and charge carrier properties. Our theoretical method has nicely reproduced the experimental data of pristine BiVO4, which encouraged us to elaborate further its Ov and Se-doped characteristics. It is found that both the Ov (1% Oxygen vacancy) and Se-doped BiVO4 (1–2% Se) have ideal band edges, band gaps, and small effective masses of electrons and holes, responsible for high photocatalytic activities. Moreover, Se-doped BiVO4 behave as p-type semiconductor. Finally, the photocatalytic water-splitting behaviour of the selected surfaces were counterchecked with water interaction, where the strong water adsorption energy of about ∼−38 to −50 kcal/mol, confirms and predicts their higher efficiencies compared to that of parent BiVO4.The financial support was provided by Engineering and Physical Science Research Council, UK (EPSRC) under the research grant No EP/P510956/1

Fabrication of Bi2 WO6 photoelectrodes with enhanced photoelectrochemical and photocatalytic performance

This is the final version. Available from Elsevier via the DOI in this record.Visible light active semiconductor Bi 2 WO 6 photoelectrodes with desired physical and chemical properties are sought for solar energy conversion and photocatalytic applications. The porous nanostructured Bi 2 WO 6 photoelectrodes are prepared by Spray Pyrolysis (SP). A detail study has been conducted to correlate the annealing temperature, morphology and crystallographic orientation with the photoelectrochemical (PEC), electrochemical and photocatalytic properties. The photoelectrodes possess an optical bandgap of 2.82 eV and exhibit anodic photocurrent. The current-voltage characterization of Bi 2 WO 6 photoelectrodes reveals that the photocurrent density and photocurrent onset potential is strongly dependent on the deposition parameters. The PEC study shows that the photoelectrode annealed at 525 °C has photocurrent density of 42 μAcm −2 at 0.23 V (vs Ag/AgCl/3M KCl) under AM1.5 illumination and exhibit superior photocatalytic activity for Rhodamine B (RhB) degradation. The electrochemical study shows that the photoelectrode has flatband potential of 2.85 V which is in good agreement with photocurrent onset potential. This finding will have a significant influence on further exploitation of Bi 2 WO 6 as a potential semiconductor material in solar energy conversion and photocatalytic applications.The Saudi Arabian Cultural BureauEngineering and Physical Sciences Research Council (EPSRC

Structural and electronic properties of oxygen defective and Se-doped p-type BiVO⁠4(001) thin film for the applications of photocatalysis

This is the final version. Available on open access from Elsevier via the DOI in this record.There is another record in ORE fro this publication: http://hdl.handle.net/10871/30528Monoclinic BiVO4 is being used as a photocatalyst due to its stability, cost-effectiveness, ease of synthesis, and narrow band gap. Although, the valence band maximum, VBM (∼−6.80 eV vs vacuum) of BiVO4 is well below the redox potential of water but having less positive conduction band minimum, CBM (−4.56 eV vs vacuum), responsible for its low efficiency. We have carried out a comprehensive periodic density functional theory (DFT) simulations for the pristine, Oxygen defective (Ov) and Se doped BiVO4, to engineer not only its CB edge position but the overall photocatalytic and charge carrier properties. Our theoretical method has nicely reproduced the experimental data of pristine BiVO4, which encouraged us to elaborate further its Ov and Se-doped characteristics. It is found that both the Ov (1% Oxygen vacancy) and Se-doped BiVO4 (1–2% Se) have ideal band edges, band gaps, and small effective masses of electrons and holes, responsible for high photocatalytic activities. Moreover, Se-doped BiVO4 behave as p-type semiconductor. Finally, the photocatalytic water-splitting behaviour of the selected surfaces were counterchecked with water interaction, where the strong water adsorption energy of about ∼−38 to −50 kcal/mol, confirms and predicts their higher efficiencies compared to that of parent BiVO4.Engineering and Physical Sciences Research Council (EPSRC

Highly Efficient Nanostructured Bi2WO6 Thin Film Electrodes for Photoelectrochemical and Environment Remediation

This is the final version. Available on open access from MDPI via the DOI in this recordNanostructured Bi2WO6 thin film electrodes with enhanced solar energy conversion and photocatalytic properties have been fabricated using Aerosol-Assisted Chemical Vapor Deposition (AACVD). By conveniently controlling the deposition process parameters, Bi2WO6 electrodes were fabricated with nanoplates and hierarchical buckyball-shaped microsphere structures morphology. A detailed study has been conducted to correlate the structure and morphology with the photoelectrochemical (PEC) and photocatalytic dye degradation performance. The PEC investigations revealed that the hierarchical buckyball-shaped microsphere structured Bi2WO6 electrodes have shown the photocurrent density of 220 μAcm-2 while nanoplates have a photocurrent density of 170 μAcm-2 at 0.23 V (vs. Ag/AgCl/3M KCl) under AM1.5 illumination. The PEC characterization of Bi2WO6 electrodes also reveals that the photocurrent density and photocurrent onset potential is strongly dependent on the orientation and morphology, hence the deposition parameters. Similarly, the methylene blue (MB) and rhodamine B (RhB) photodegradation performance of Bi2WO6 electrodes also show a strong correlation with morphology. This finding provides an appropriate route to engineer the energetic and interfacial properties of Bi2WO6 electrode to enhance solar energy conversion and the photocatalytic performance of semiconductor materials.Engineering and Physical Sciences Research Council (EPSRC)UK-India Education and Research Initiative (UKIERI

Photoelectrochemical properties of texture-controlled nanostructured α-Fe2O3 thin films prepared by AACVD

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Nanostructured α-Fe2O3 thin film electrodes were deposited by aerosol-assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α-Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current-voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 μA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C

Donor-acceptor polymer for the design of All-Solid-State dye-sensitized solar cells

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordDensity functional theory study has been carried out to design a new All-Solid-State dye-sensitized solar cell (SDSC), by applying a donor-acceptor conjugated polymer instead of liquid electrolyte. The typical redox mediator (I1−/I3−) is replaced with a narrow band gap, hole transporting material (HTM). The electronic and optical properties predict that donor and acceptor moieties in the polymeric body have increased the visible light absorption and charge transporting ability, compared to their parent polymers. A unique “upstairs” like band energy diagram is created by packing N3 between HTM and TiO2. Upon light irradiation on the proposed configuration, electrons will move from the dye to TiO2 and from HTM to dye (to regenerate dye), simultaneously. Our theoretical simulations prove that the proposed configuration will be highly efficient as the HOMO level of HTM is 1.19 eV above the HOMO of sanitizer (dye); providing an efficient pathway for charge transfer. High short-circuit current density and power conversion efficiency is promised from the strong overlapping of molecular orbitals of HTM and sensitizer. A low reorganization energy of 0.21 eV and exciton binding energy of 0.55 eV, confirm the high efficiency of HTM. Finally, a theoretical open-circuit voltage of 1.49 eV would results high quantum yield while, the chemical stability of HTM towards oxidation can be estimated from its high ionization potential value (4.57 eV)

Density Functional Theory Study of Selenium-Substituted Low-Bandgap Donor-Acceptor-Donor Polymer

This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this recordTheoretical study of an optically transparent, near-infrared-absorbing low energy gap conjugated polymer, donor-acceptor-donor (D-A-D), 2,1,3-benzosele-nadiazole (A) as acceptor and 3,4-ethylenedioxyselenophene (D) as donor fragments, with promising attributes for photovoltaic application is reported herein. The D and A moiety on the polymeric backbone has been found to be responsible for tuning the band gap, optical gap, open circuit (VOC), and short-circuit current density (JSC) in the polymers solar cells. D-A-D has a key role in charge separation and molecular architecture which ultimately influences the charge transport. Reduction in the band gap, high charge transformation, and enhanced visible light absorption in the D-A-D system is because of strong overlapping of molecular orbitals of D and A. The polaron and bipolaron effects are also investigated which has a direct relation with visible light photocurrent generation. In addition, the enhanced planarity and weak steric hindrance between adjacent units of D-A-D resulted in red-shifting of its onset of absorption. The simulated band gap of the D-A-D has excellent correlation with experimentally reported values for closely related systems, which validates the level of theory used. Finally, PSC properties of the designed D-A-D was modeled in the bulk heterojunction solar cell, which gives a theoretical VOC of about 1.02 eV. (Graph Presented)

The prevalence of hyperthyroidism at university of maiduguri teaching hospital (UMTH), Maiduguri.

Hyperthyroidism and hypothyroidism are the two common thyroid disorders but there is paucity of information on the prevalence of hyperthyroidism in Nigeria in general and in Northeast of Nigeria in particular. Objective: To determine the prevalence of hyperthyroidism at University of Maiduguri Teaching Hospital. Method: A retrospective study done over a period of one year that reviews the results of serum TSH, T4 and T4 from 203 patients. Results: Eighty-nine (43.8%) and 79 (38.9%) patients had elevated serum levels of T3 and T4 respectively (i.e. were hyperthyroid), 114 (56.2%) and 112 (55.2%) patients had normal serum levels of T3 and T4 respectively (i.e. were euthyroid) while 12 (5.9%) patients had low serum levels of T4 only (i.e. were hypothyroid). The female to male ratio of hyperthyroidism was 4 and 1[T3 — female 68 (35.4%), male — 17(89%); T 4— female 59 (30.7%), male 15(7.8%)]. Age —group from 25—34 years was the most frequent. (51 patients) and with the highest prevalence of hyperthyroidism [T4- 19(14.2%); T4 18(13.4%)].The study further revealed a decline in the prevalence of hyperthyroidism as age increased. The finding of high prevalence of low TSH (20.8%) against high prevalence of elevated T3 and T4 [89(44.1% and 79(38.9%) respectively] in this study could suggest that the hyperthyroidism in the studied patients could have been largely caused by Graves' disease. Conclusion: This study revealed that thyroid disorders are not uncommon in our environment and the finding of high prevalence of low TSH above high TSH, suggested that the hyperthyroidism discovered in our study may have been largely caused by Grave's disease. We recommend that more laboratory diagnostic centre should be established in our environment where thyroid disorders can be diagnosed

Electronic properties of Β-TaON and its surfaces for solar water splitting

This is the final version of the article. Available from Elsevier via the DOI in this record.Recently, oxynitrides materials such as β-TaON has been using as a photoanode material in the field of photocatalysis and is found to be promising due to its suitable band gap and charge carrier mobility. Computational study of the crystalline β-TaON in the form of primitive unit cell, supercell and its N, Ta, and O terminated surfaces are carried out with the help of periodic density functional theory (DFT). Optical and electronic properties of all these different species are simulated, which predict TaON as the best candidate for photocatalytic water splitting contrast to their Ta 2 O 5 and Ta 3 N 5 counterparts. The calculated bandgap, valence band, and conduction band edge positions predict that β-TaON should be an efficient photoanodic material. The valence band is made up of N 2p orbitals with a minor contribution from O 2p, while the conduction band is made up of Ta 5d. Turning to thin films, the valence band maximum; VBM (−6.4 eV vs. vacuum) and the conduction band minimum; CBM (−3.3 eV vs. vacuum) of (010)-O terminated surface are respectively well below and above the redox potentials of water as required for photocatalysis. Charge carriers have smaller effective masses than in the (001)-N terminated film (VBM −5.8 and CBM −3.7 eV vs. vacuum). However, due to wide band gap (3.0 eV) of (010)-O terminated surface, it cannot absorb visible wavelengths. On the other hand, the (001)-N terminated TaON thin film has a smaller band gap in the visible region (2.1 eV) but the bands are not aligned to the redox potential of water. Possibly a mixed phase material would produce an efficient photoanode for solar water splitting, where one phase performs the oxidation and the other reduction.We acknowledge the financial support of Engineering and Physical Science Research Council, UK (EPSRC)under the research grant Nos. EP/P510956/1, EP/P003435/1 and EP/R512801/1. S.K acknowledges the Notur Norwegian supercomputing facilities through project nn4608k and the HyMatSiRen project 272806 by the Research Council of Norway. We also acknowledge Prof. Neil Allan and Dr. Sergio C. Espindola for their help in completing this work