Influence Of Thiourea Research Articles

A highly efficient method for characterizing the kinetics of hydrogen evolution reaction

PurposeThe purpose of this study is to provide a highly efficient method to obtain the kinetics of the hydrogen evolution reaction (HER) on metal electrodes in an alkaline solution and to analyze the effect of thiourea addition on HER under the same cathodic overpotential.Design/methodology/approachA novel method based on hydrogen permeation tests, potentiodynamic polarization tests and electrochemical impedance spectroscopy was put forward to characterize the HER kinetics on metal electrode.FindingsThe study found that adding thiourea accelerated the Volmer, Heyrovsky and Tafel reactions associated with HER. In addition, it reduced the hydrogen surface coverage and increased the hydrogen permeation steady-state current density. As a result, thiourea facilitated HER, promoted the diffusion of hydrogen atoms into iron and reduced the number of hydrogen atoms in the adsorbed state.Originality/valueThis work provides novel insights into the influence of thiourea on HER kinetics, demonstrating that thiourea addition can significantly enhance HER efficiency by altering reaction dynamics and promoting hydrogen atom diffusion into iron. This has implications for hydrogen energy applications, cathodic protection and understanding hydrogen embrittlement mechanisms.

Influence of thiourea and salicylic acid on yield and quality parameters of corms and cormels of gladiolus

Influence of thiourea and salicylic acid on yield and quality parameters of corms and cormels of gladiolus

Theoretical calculations and electrochemical investigation of additives in aqueous methanesulfonic acid for lead electrodeposition

The methanesulfonate system is gradually replacing the traditional highly polluting fluoride electroplating lead （Pb） system with its eco-friendly advantage, and searching for suitable additives is crucially important to obtain uniform Pb coatings in the methanesulfonate system. In this work, a potential additive of thiourea suitable for methanesulfonate-based Pb electroplating was screened based on the theoretical calculations and cyclic voltammetry tests, and the effect of thiourea in the Pb electrodeposition was investigated. Specifically, the adsorption-coordination mechanism was proposed to explain the effect of thiourea by calculating the Bader charge density difference of thiourea on Pb surface and its interaction with Pb2+. Meanwhile, the effects of thiourea on the electrochemical behavior of lead electrodeposition were investigated by cyclic voltammetry and chronoamperometry. The nucleation and growth of Pb follow 3D diffusion-controlled progressive nucleation at the low potential and high thiourea concentration but follow 3D diffusion-controlled instantaneous nucleation at the high overpotential. The appropriate concentration of thiourea could improve the surface morphology of lead coating and make the layer flat and dense. The influence of thiourea on the crystalline orientation and grain size of the coating was analyzed, which indicated that the increase of thiourea concentration favored the formation of the Pb (220) crystal plane and the decrease of grain size.

Influence of thiourea in the precursor solution on the structural, optical and electrical properties of CZTS thin films deposited via spray coating technique

CZTS films were prepared by spray coating using non-aqueous precursor solutions with and without sulphur source and studied their structural, optical and electrical properties. The films prepared by both the routes were sulphurized at different temperatures to study the effect of temperature on the phase formation. Phase purity was confirmed by XRD, Raman analysis and Rietveld refinement technique. The studies revealed proper phase and crystallinity for the films of both routes sulphurized at 550 °C. These films exhibited dense and improved grain structure, optimal bandgap and higher absorption coefficient. The non-thiourea films sulphurized at 550 °C had a carrier concentration of 1.544 × 1019 cm−3, mobility of 0.87 cm2V−1 s−1 and resistivity of 0.46 Ω·cm, while the thiourea films achieved carrier concentration, mobility and resistivity of 3.67 × 1019 cm−3, 0.33 cm2V−1 s−1 and 0.52 Ω·cm, respectively. The comparative study demonstrates that the films under investigation have the potential for the fabrication of efficient solar cells.

Influence of thiourea on electroless Ni–P films deposited on silicon substrates

Electroless nickel–phosphorus films were produced on silicon substrates in alkaline bath solutions, with the addition of thiourea in a concentration range of 1.0–5.0 mg L−1. The influence of thiourea on the chemical composition, morphology and corrosion resistance of the films was studied. The results revealed thiourea had a major influence on plating rate, phosphorus-content and aggregate size. The optimal content of thiourea was 1 mg L−1. Thiourea accelerated the deposition rate at low concentration of 1 mg L−1, but deceased the deposition rate and the phosphorus content at high concentration. The surface of the film without thiourea was smooth and dense. Also, with increasing thiourea content, the surface evolved into coarse nodular morphology with clear intercolonial boundaries. With the addition of 1 mg L−1 thiourea, the film had better corrosion resistance compared to film without thiourea.

Influence of thiourea on the synthesis and characterization of chemically deposited nano structured zinc sulphide thin films

Nanocrystalline ZnS thin films incorporated onto glass substrates by chemical bath deposition method were investigated by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV–Visible Spectroscopy (UV–Vis), Photoluminescence (PL), and Raman Spectroscopy (FT-R) studies. The influence of thiourea on the structural and optical properties of ZnS films was discussed in detail. The X-ray diffraction patterns confirmed the rhombohedral structure of ZnS thin films. AFM measurements indicated the nano carpet-like surface morphology variation in film with influence of thiourea. The optical absorption studies in the wavelength range of 200–800 nm showed that the band gap energy of ZnS has decreased from 3.69–3.36 eV, as thiourea varied from 0.2–0.8 M. The PL spectra divulged a shift near band edge emission around 360 nm, when thiourea concentration was increased. The Stokes shift calculations from PL emission spectra supported the relative intensities estimated from PL energy band spectra and showed a dependable repeatability for different molar concentrations. The Zn–S complexes were identified in the Raman spectra and the Raman spectral shift for 0.6 M composition of thiourea, which was found to be appreciable for ZnS thin films. The characterization studies clearly exposed the effect of thiourea onto the chemically deposited ZnS thin films.

Metallic 1T-MoS2 with defect induced additional active edges for high performance supercapacitor application

Influence of thiourea on the formation of active-edges and the metallic phase of MoS2 and investigation of its energy storage properties.

Growth, optical and thermal studies of pure and thiourea doped ammonium pentaborate nonlinear optical single crystals

Single crystals of pure and thiourea doped ammonium pentaborate have been successfully grown by slow solvent evaporation technique. The growth conditions and surface morphology of pure and thiourea doped single crystals of APBO are optimised and the grown crystals are confirmed by X-ray diffraction. The crystals are characterised by Fourier transform infrared spectroscopy and UV-vis-NIR spectral techniques. The grown crystals of pure and thiourea doped APBO are subjected to thermal studies. The thermogravimetry and derivative thermogravimetry studies confirm that the decomposition of pure and doped crystals takes place in three different stages making them suitable for device fabrication for frequency conversion applications. The second harmonic generation of the crystals are confirmed by Nd∶YAG pulsed laser employing Kurtz powder technique and the influence of thiourea is also discussed. The Vicker microhardness test was carried out on the grown crystals to study the mechanical strength therein the Vicker’s hardness number (Hv) and Work hardening coefficient (n) were calculated.

The effect of thiourea, l(−) cysteine and glycine additives on the mechanisms and kinetics of copper electrodeposition

The influence of thiourea, l(−) cysteine and glycine on the mechanisms and kinetics of copper electrodeposition from aqueous solution at pH 1.00 ± 0.05 and 25 °C was investigated using several complementary techniques. Rotating disc electrode current density measurements and the kinetic parameters calculated from Koutecký–Levich analysis indicated that at 5 × 10−3 M thiourea and l(−) cysteine addition the electro-reduction of Cu(II) was significantly inhibited. By contrast, upon similar addition of glycine, the reduction current density increased and the equilibrium potential moved towards more positive values. Microscopic imaging studies of the resulting Cu films showed that thiourea and l(−) cysteine led to fine-grained deposits, whilst glycine addition resulted in a coarser deposit. It is suggested the additives substantially altered the electron and mass transfer processes during electrodeposition. Both thiourea and l(−) cysteine appear to act by specific chemical interactions that lead to CuS co-crystallization. On the other hand, glycine is believed to act by mediating the Cu(II) to Cu(I) reduction process.

Hydrothermal synthesis of WO3·0.5H2O microtubes with excellent photocatalytic properties

Pyrochlore WO3 microtubes were synthesized via a hydrothermal method for the first time. In this process, thiourea was employed to overcome the hydrogen bonds on the rim of WO3·0.5H2O and hydroxylamine hydrochloride was used as a viscosity regulator. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy observations revealed that large amounts of uniform single-crystal WO3·0.5H2O microtubes with diameters ranging from 100 to 300nm and length of tens of micrometers were obtained. The thickness of the tube wall was about 40nm. A possible rolling mechanism was proposed to explain the formation of the tubular structures, and the influence of thiourea and hydroxylamine hydrochloride on the uniform tubular morphology was discussed. The WO3·0.5H2O microtubes showed excellent photocatalytic activity toward the degradation of organic molecules such as RhB, which may find potential applications in the fields of photocatalysts, sensors and transistors.

Preparation, characterization, and electrochemical studies of sulfur-bearing nickel in an ammoniacal electrolyte: the influence of thiourea

Sulfur-bearing nickel was prepared by a direct electrodeposition in an ammoniacal Ni(II) electrolyte containing thiourea. This sulfur-bearing nickel showed an excellent dissolving activity when used as anodic materials in the traditional Watt bath. The influence of thiourea on the surface microstructure, crystallization texture, and electrocrystallization process of sulfur-bearing nickel were investigated by scanning electron microscopy, X-ray diffraction, and electrochemical techniques. The results show that the S element is uniformly distributed in the electrodeposited nickel. The prepared nickel samples present a blade shape microstructure, and the blade size decreases by the addition of thiourea. Sulfur-bearing nickel exhibits face-centered cubic structure and (111) preferred orientation, and the orientation distribution is strengthened with increased thiourea concentration. The nucleation parameters, such as N0, A, and J0, are obtained from the initial parts of the transients making use of Sharifker–Mostany theoretical model. Both the nucleation rate and the vertical growth rate are increased by the addition of thiourea, leading to finer grains and better dissolving activity.

Copper electrodeposition onto hydrogenated Si(111) surfaces: Influence of thiourea

Kinetics of initial steps of copper electrodeposition onto hydrogen terminated n-Si(1 1 1) surfaces from sulfuric acid electrolyte, was obtained using cyclic voltammetry and potentiostatic transients. Capacitance measurements at different potentials in Cu2+ ion-free solutions with different thiourea concentrations were used to determine the flat band potential of n-Si(1 1 1) substrates. The analysis of the j/t transients according to existing theories indicates that copper deposition occurs by three-dimensional nucleation followed by diffusion controlled growth of nuclei. The presence of thiourea (TU) produces an inhibition of the copper electrocrystallization. Adsorption of the additive on the hydrogenated substrate is evidenced by the changes observed in the flat band potential of the Si(1 1 1)–H surface. Copper deposition kinetics from TU-containing solutions corresponds to a progressive nucleation with diffusion controlled crystal growth. From analysis of current transients at different overpotentials, nucleation rates of copper deposition for additive-free and TU-containing solutions were determined.

Influence of ammonium selenate and thiourea mixture on mechanical properties and morphology of Zn–Mn alloy coatings electrodeposited from sulphate–citrate bath

The influence of thiourea (TU, 0·5 g L−1) and additive mixture of ammonium selenate and thiourea (AS–TU, 0·5 g L−1) on electrodeposition of Zn–Mn alloy coatings from sulphate–citrate bath (SCB) has been studied. Investigations of alloy composition were carried out by atomic absorption spectroscopy and inductively coupled plasma. A profile of the relative concentration of sulphur was obtained using glow discharge spectroscopy. The morphology of the coatings was studied by scanning electron microscopy. The crystal structure was investigated by X-ray diffraction. Two phases (metastable ϵ and β) were detected in coatings electrodeposited from SCB with TU and mixture of AS–TU at jc≥10 A dm−2 (≥50%Mn). Zn–Mn alloy coatings, electrodeposited from an SCB with 0·5 g L−1 TU were harder than coatings electrodeposited from SCB with AS alone, and a mixture of AS–TU. Coatings electrodeposited from SCB with a mixture of AS–TU had the lowest tensile stress.

The influence of thiourea on copper electrodeposition: Adsorbate identification and effect on electrochemical nucleation

The effect of thiourea on copper deposition onto a copper seed layer from an electrolyte composed of CuSO 4, H 2SO 4, deionized water, and thiourea was investigated. Even in the presence of very low concentrations of thiourea, extremely smooth and bright copper deposits were obtained. From the results of X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electrochemical analyses, thiourea was found to react with copper or copper ions leading to the generation of CuS. CuS adsorption onto the copper seed layer seemed to inhibit the initial nucleation of the copper adions, resulting in the formation of smaller Cu grains compared to those forming in the absence of thiourea. CuS was observed to cover all active sites of the 1 cm 2 copper seed layer above 0.017 g/L thiourea. The surface roughness as well as the mean grain size of the deposits also approached minimum values above this thiourea concentration. Adsorbed CuS was incorporated into the deposits during electroplating, which was believed to be the major factor for the increased resistivity of the deposits.

Electrochemical oxidation of borohydride on platinum electrodes: The influence of thiourea in direct fuel cells

The electrochemical behaviour of sodium borohydride on a platinum electrode in the absence and presence of thiourea (TU) was investigated by cyclic voltammetry. In the absence of thiourea, several overlapping peaks associated with the hydrolysis of BH 4 − appear in the domain of hydrogen oxidation, i.e., in the potential range of −1.25 to −0.50 V versus Ag/AgCl. As a consequence of secondary reactions, the borohydride oxidation in 3 M NaOH solution shows a four to six-electron process, according to its concentration, in direct fuel cells. A conveyable TU/NaBH 4 concentration ratio of 0.6 inhibits the delivery of hydrogen simultaneously with catalytic hydrolysis of BH 4 −. Thus, the coulombic efficiency in direct fuel cell discharge was increased showing an about eight-electron process for the oxidation of BH 4 −.

Biosorption of platinum and palladium for their separation/preconcentration prior to graphite furnace atomic absorption spectrometric determination

Inexpensive baker's yeast Saccharomyces cerevisiae and green algae Chlorella vulgaris, either free or immobilized on silica gel have been shown to selectively accumulate platinum and palladium from water samples in acidic medium (pH 1.6–1.8). Optimization of conditions of metals biosorption (sample pH, algae and yeast masses, adsorption time, temperature) was performed in batch mode. The procedure of matrix separation based on biosorption of platinum and palladium on algae C. vulgaris covalently immobilized on silica gel in flow mode was developed. The use of algae in flow procedure offers several advantages compared with its use in the batch mode. The procedure shows better reproducibility (<2%), improved efficiency of platinum retention on the column (93.3±1.6%), is less laborious and less time consuming. The best recovery of biosorbed metals from column (87.7±3.3% for platinum and 96.8±1.1 for palladium) was obtained with solution of 0.3 mol l −1 thiourea in 1 mol l −1 hydrochloric acid. The influence of thiourea on analytical signals of examined metals during GFAAS determination is discussed. The procedure has been applied for separation of noble metals from tap and waste water samples spiked with platinum and palladium.

Studies of the Effect of Thiourea on the Electroreduction of In(III) Ions in Perchloric Acid

The influence of thiourea on the electroreduction of In(III) ions on mercury electrode in perchloric acid solution was examined. It was observed, that thiourea can catalyze the electroreduction of In(III) ions. The presence of thiourea leads to multistage reaction where transfer of the first electron is principally catalyzed. Catalytic activity of thiourea is connected with its ability to remove molecules of coordinated water as well as with forming of active complexes of indium ions on the surface of electrode, facilitating transfer of electrons.

Studies of the Accelerating Effect of Thiourea on the Reduction of ZnII in Mixed Water–Organic Solvents at the Mercury Electrode

The accelerating influence of thiourea on the Zn II /Zn(Hg) reduction process was investigated in the following mixed solutions: water-methanol (MeOH); water-ethanol (EtOH); water-dimethyl sulphoxide (DMSO); water-dimethylformamide (DMF). It was suggested that the dominant role in acceleration of the electrode process is played by the composition of the activated complex, which is presumably composed of solvent molecules and thiourea molecules adsorbed on to the electrode. A mechanism was proposed for the process occurring.

The Influence of Thiourea on the Two-Step Electroreduction of Zn(II) Ions

The two-step reduction of Zn(II) ions at a dropping mercury electrode in 1 M NaClO4/0.001 M HClO4 in the presence of thiourea was examined in wide potential and frequency ranges using the impedance method. The catalytic activity of thiourea concerns both electron transfer steps. It was found that the acceleration of the electroreduction process depends on the surface concentration of thiourea.

Influence of Thiourea and Its Derivate on the Process of Cathodic Electrodeposition of Copper

Influence of Thiourea and Its Derivate on the Process of Cathodic Electrodeposition of Copper