Enhanced photoelectrochemical activity of electrochemically deposited ZnO nanorods for water splitting reaction

This paper reports the development of zinc oxide films electrodeposited at different potentials on tin-doped indium oxide substrates. The effect of deposition potential on ZnO microstructure, optical absorption, and photocatalytic activity for water splitting reaction were studied in detail. The films were potentiodynamically grown by applying different deposition potentials, such as - 0.7, - 0.8, and - 0.9 V at constant temperature (70 °C) for 30 min. The pH of precursor solution was maintained around 6 during the electrodeposition process. X-ray diffraction study revealed the hexagonal wurtzite crystal structure of the ZnO. The field emission scanning electron microscopy (FESEM) demonstrated a significant variation in the microstructure with changing deposition potential. UV–Visible spectroscopy demonstrated a significant change in the optical band gap values for the ZnO films deposited at different deposition potentials. The highest photocatalytic activity of water splitting was recorded for the films deposited at - 0.8 V under AM. 1.5 G solar light illumination. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.FDK-2014-3488Acknowledgements The authors acknowledge the financial support of the Scientific and Technological Research Council of Turkey under (TUBITAK-BİDEB) 2211-National Ph.D. Fellowship Programme and Scientific Research Project of Cukurova University (Project No: FDK-2014-3488)

Effect of Sr doping on the electronic band structure and optical properties of ZnO: A first principle calculation

Incorporating impurities in ZnO provide opportunities to manipulate its electronic and optical properties, which can be exploited for optoelectronic device applications. Among various elements doped in ZnO crystal structure, limited attempts have been accounted for the Sr-doped ZnO system. Further, no theoretical evidence has been reported so far to explore the Sr-doped ZnO frameworks. Here, we report first principle study for the pure and Sr-doped ZnO (Zn1-xSrxO) structure. We employed the Perdew-Burke-Ernzerhof exchange-correlation function parameters in generalized gradient approximations. In light of these estimations, we calculated the electronic band gap, density of states, and optical parameters, for example, absorption, dielectric functions, reflectivity, refractive index, and energy-loss. The studies suggested that Sr incorporation expanded the optical band gap of ZnO. In addition, the energy-loss significantly increased with Sr content which might be associated with an increase in the degree of disorder in the crystal lattice with Sr incorporation. Also, significant changes were seen in the optical properties of ZnO with Sr content in the low energy region. The theoretical results were likewise compared with the previously reported experimental data. © 2017 Author(s).116C035We acknowledge the financial support by the Scientific and Technological Research Council of Turkey (TUBITAK Project No. 116C035) under the 2236-Co-Funded Brain Circulation Scheme

The investigation of Cu2O electrochemical deposition time effect on ZnO for water splitting

The renewable hydrogen production has been immense research area, converting solar light to hydrogen in PEC applications. Both ZnO and Cu2O are lower cost material for commercialization on PEC. Herein, Cu2O electrochemical deposition time effect was investigated on ZnO nanorod arrays (NRAs) for water splitting with solar light irradiation (10, 20, 30 and 40 min). The deposition duration is attributed to the photocatalytic performance for hydrogen production. FESEM and UV–vis results suggest that the deposition duration plays a key role in surface structure and absorption of light, respectively. Both electrochemical impedance spectroscopy and linear sweep voltammetry indicate that ZnO/Cu2O-20 min electrode is the lowest Rp value (25486 ? cm-2) and the highest current-density (0.64 mA cm-2 at 0.5 V vs. Ag/AgCl reference electrode), respectively. This paper gives understanding into long-time electrochemical deposition of Cu2O on ZnO NRAs for water splitting via solar light irradiation. © 2019 Elsevier B.V.FDK-2014-3488 Türkiye Bilimsel ve Teknolojik Araştirma KurumuThe authors acknowledge the financial support by the Scientific and Technological Research Council of Turkey under ( TUBITAK- BİDEB ) 2211- National Ph.D. Fellowship Program and Scientific Research Project of Cukurova University (Project No: FDK-2014-3488 )

Electrocatalytic behavior of the Pd-modified electrocatalyst for hydrogen evolution

The hydrogen evolution behavior of C/CoSn, C/CoSnZn and C/CoSnZn-Pd catalysts which were prepared on a graphite substrate (C) by electrochemical deposition, as well as their electrochemical properties in the KOH solutions, have been investigated by the polarization measurements, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and electrolysis techniques. C/CoSnZn catalyst was etched in caustic to leach out zinc and to produce the Raney-type, porous electrocatalytic surface for hydrogen evolution. In order to further improve the catalytic activity of the C/CoSnZn catalyst for the hydrogen evolution reaction (HER), this catalyst was modified by loading a small amount of Pd. Results showed that the modification of C/CoSnZn catalyst by deposition of a small amount of Pd can render cathode material very active in hydrogen evolution. High catalytic activity of the C/CoSnZn-Pd catalyst depends on the surface porosity, large specific surface area and well known intrinsic catalytic activity of Pd. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.This study has been financially supported by the Çukurova University research fund. The authors are greatly thankful to Çukurova University research fund

Molybdenum disulfide as the interfacial layer in the CuO–TiO2 photocathode for photoelectrochemical cells

Photoelectrochemical cells guarantee the production of hydrogen as the clean energy source to overcome energy crisis. In this study, we have explored the impact of MoS2 as the interfacial layer in the CuO–TiO2 composite photocathode framework. The CuO was electrodeposited on the indium tin oxide (ITO) coated glass substrates and subsequently treated at high temperature (550 °C for 2 h) to develop CuO. The fitting of electrochemical impedance spectroscopy data revealed a decrease in the magnitude of total impedance (|Z|) for the composite photocathode with MoS2 as the interfacial layer between the CuO and TiO2. The magnitudes of charge transfer resistance for the ITO/CuO, ITO/CuO/TiO2, and ITO/CuO/MoS2/TiO2 electrodes were calculated as 429,170, 18,490, and 17,388 ? cm-2, respectively. Likewise, the photocurrent density was increased with the addition of MoS2 at the interface up to -0.73 mA cm2 which was recorded -0.39 mA cm2. This study is critical for the future improvement of the potential photocathode materials with enhanced photocurrent response. © 2017, Springer Science+Business Media New York

Thermal decomposition of sol-gel derived Zn0.8Ga0.2O precursor-gel: A kinetic, thermodynamic, and DFT studies

Gallium-doped zinc oxide has been widely accepted as the potential alternative to expensive tin-doped indium oxide (ITO) for transparent conductive layer applications. An extensive study reports the processing of ZnO-based semiconductor materials by utilizing a sol-gel method, however, no study has been reported to investigate both the kinetic and thermodynamic aspects of the gel decomposition for these materials. Here, we studied the kinetic and thermodynamic parameters of the sol-gel derived Zn0.8Ga0.2O precursor gel decomposition utilizing the thermogravimetric (TG) and differential thermal analysis (DTA). A non-isothermal method was used to calculate the activation energy, pre-exponential factors, reaction mechanism function, and order of reaction. In addition, density functional theory (DFT) was used to calculate the optical band gap and density of states. The results suggested that the gel decomposition followed the Jander: 3D model. The study is important for understanding the components of synthesis ranging from the formation of an activated complex to gel decomposition, while this study can be extended to other semiconductor processing methods. © 2018116C035The authors acknowledge the financial support by the Scientific and Technological Research Council of Turkey ( TUBITAK Project No: 116C035 ) under the 2236-Co-Funded Brain Circulation Scheme

Optimizing copper oxide layer on zinc oxide via two-step electrodeposition for better photocatalytic performance in photoelectrochemical cells

The microstructure of copper oxide layer on zinc oxide is optimized via a two-step electrodeposition method to create potential composite electrodes for photoelectrochemical cells. By optimizing the deposition temperature, the microstructure and photocatalytic properties can be fundamentally modified. The strategy includes the potentiostatic deposition of zinc oxide layer in the initial step following galvanostatic deposition of copper oxide at selected bath temperature, including 30, 40, 50, and 60 °C. In all cases, the copper oxide layer deposited at 40 °C significantly improves the photoanodic current density. Also, the microstructure and optoelectrical properties of the composite films are characterized by electron microscopy, impedance spectroscopy, Mott–Schottky, and solar simulation measurements. It is found that variation in copper oxide deposition temperature affects the electron-hole recombination process and photocatalytic performance. © 2019 Elsevier B.V.FDK-2014-3488The authors acknowledge the financial support by the Scientific and Technological Research Council of Turkey under (TUBITAK- BİDEB) 2211- National Ph.D. Fellowship Program and Scientific Research Project of Cukurova University (Project No: FDK-2014-3488 )

Photoelectrochemical characteristics of CuO films with different electrodeposition time

This paper explores the effect of electrodeposition time on microstructure, optical, and photoelectrochemical properties of CuO films. CuO films were electrochemically deposited on tin-doped indium oxide (ITO) substrates using a Cu2O electrodeposition method followed by annealing at 550 °C for 2 h. The electrochemical deposition was carried out at different times (300, 600, 1200, and 1800 s) utilizing a copper sulfate pentahydrate and lactic acid solution. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to perform phase and microstructure analysis. Photoluminescence (PL) studies confirmed an increase in emission intensities with increasing deposition time. In addition, a significant change was observed in photoelectrochemical properties of the film by varying the deposition time. The film deposited for 600 s showed a high photocurrent density of -0.55 mA cm-2 at -0.5 V. Moreover, a lowest resistance from electrochemical impedance spectroscopy (EIS) was recorded for the films electrochemically deposited for 600 s. © 2017 Hydrogen Energy Publications LLC116C035The authors acknowledge the financial support by the Scientific and Technological Research Council of Turkey (TUBITAK Project No: 116C035) under the 2236-Co-Funded Brain Circulation Scheme

Comprehensive investigation of butyl stearate as a multifunctional smart concrete additive for energy-efficient buildings

Using of phase change materials (PCM) for increasing energy savings in sustainable buildings is receiving a lot of interest in commercial applications. Butyl stearate (BS), as PCM, can be used to maintain ambient temperature in the human comfort zone and prevent temperature fluctuations by enhancing the thermal properties of concrete. The long-term effects of BS on concrete are not well known. In this study, the applicability of BS, as a smart concrete additive, by direct incorporation in the concrete structure was investigated comprehensively including thermal, rheological, and corrosion behaviour. The thermal characterization of PCM was achieved using DSC, TGA, thermal conductivity, and thermal buffering experiments. Thermal storage capacity of BS was measured to be 134.2 J/g, which is high enough to be used for passive solar energy storage in buildings. The fresh concrete experiments revealed that workability and flowability of fresh concrete mixes were improved. The maximum hydration temperature was reduced, and a retarding effect was observed by the addition of BS. Moreover, the corrosion behaviour of steel embedded in concrete with BS as PCM was studied in a solution of NaCl (3.5 wt%) representing an aggressive environment by utilizing electrochemical impedance spectroscopy (EIS) for long-term corrosion tests that lasted for 1 year. The open circuit potential of steel in concrete with BS showed noble potential indicating low corrosion probability. The FESEM images and polarization resistance (Rp) values showed that the addition of BS in concrete decreases corrosion of the rebar in comparison with concrete without BS. Addition of BS not only enhances thermal capacity but also exhibits corrosion protection of rebar by hindering penetration of chloride ions into the concrete. © 2019 John Wiley & Sons, Ltd.Firat University Scientific Research Projects Management Unit 111M557 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu 657466 British Association for PsychopharmacologyThe authors gratefully acknowledge the financial support from European Union's Horizon 2020 research and innovation programme under grant agreement no. 657466 (INPATH-TES), the Scientific and Technological Research Council of Turkey (TUBITAK) under project no. 111M557, the Scientific Research Projects Management Unit of Çukurova University (BAP) under project no. FDK-2015-3278, and Kambeton Company

A novel thiophene Schiff base as an efficient corrosion inhibitor for mild steel in 1.0?M HCl: Electrochemical and quantum chemical studies

This study presents the synthesis, structural characterization, and inhibition efficiency of a new sulphur containing Schiff base (4-((thiophene-2-ylmethylene)amino)benzamide) (4-TAB) on mild steel in 1.0 M HCl solution. The inhibition efficiency of the 4-TAB is analysed by using electrochemical analysis, solution assay analysis, and theoretical calculation. Electrochemical impedance spectroscopy and linear polarization resistance results show the highest inhibitor efficiency of 96.8% and 96.5%, respectively. The potentiodynamic polarization measurements indicate a decreasing corrosion rate from 9.104 to 0.481 mm year-1 by addition of 4-TAB. Theoretical calculations are performed using the density functional theory to further confirm and compare our experimental results. © 2018 Elsevier B.V.Firat University Scientific Research Projects Management Unit: FBA-2017-7056This work was supported by Çukurova University Scientific Research Project (grant numbers: FBA-2017-7056 )