Thiourea Concentration Research Articles

A Novel Approach to Study the Time-Varying Additive Activity during the Electrorefining of Copper

Electrodeposition additives are key components to enhance the electrochemical deposition of metals, either in pure plating applications or during the electrorefining of metals. Many different additives, either organic or inorganic, are applied in industry, depending on the type of process. This work focusses on thiourea and chloride as common additives used for copper electrorefining. This electrochemical industrial process consumes an impure copper anode and produces a pure (99.995 %) copper cathode, while the anode impurities remain in the electrolyte. Additives assist the electroreduction process to produce smooth copper deposits, essential to avoid short circuits and the formation of unwanted cathode morphologies which can entrap impurities.Thiourea is a crucial but complex additive in copper refining. It is known to degenerate into formamidine disulfide (FDS) and both thiourea as FDS can undergo interactions with either copper ions in the solution or the cathode surface. Time dependent additive studies and fundamental knowledge of the effect of aged electrolyte on the cathodic part of the electrorefining process are scarce.The approach applied in this work enables the investigation of the time dependent effect of additives, in this case thiourea and chlorides, assisting the electroplating of copper. Fundamental knowledge of the assisted plating process is extended to create a corner stone for applied research, subsequently, semi-industrial circumstances are used to describe the additive behaviour in industrial relevant conditions. Operando Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) is used to study the electrochemistry of the additive system [1,2]. Hereby, a multisine input signal is added to the DC current to perform the ORP-EIS experiment simultaneously with the plating process. This measurement technique allows an in situ monitoring of the electrochemical system for hour-long electrodeposition processes. The ORP-EIS technique enables a quantification of the nonlinearities and non-stationarities during the EIS experiment [3]. Additionally, the present non-stationarities are modelled and the nonlinearities are considered as nuisance factor to result in a best linear time-varying approximation [4,5]. An equivalent electrical circuit is used as model to extract the relevant physical parameters from the impedance data. The EIS study is complemented with an ex situ analysis of the thiourea concentration, through ion chromatography, as a function of plating time. Correlations could be made between electrochemical parameters and actual thiourea concentrations [2].[1] T. Collet, et al., An operando ORP-EIS study of the copper reduction reaction supported by thiourea and chlorides as electrorefining additives, Electrochimica Acta (2021) 138762. [2] T. Collet, et al., The time-varying effect of thiourea on the copper electroplating process with industrial copper concentrations, Electrochimica Acta (2022) 141412. [3] Van Gheem, et al., Electrochemical impedance spectroscopy in the presence of non-linear distortions and non-stationary behaviour part i: Theory and validation, Electrochimica Acta 49 (2004) 4753–4762. [4] N. Hallemans, et al., Detection, Classification, and Quantification of Nonlinear Distortions in Time-Varying Frequency Response Function Measurements, IEEE Transactions on Instrumentation and Measurement, 70 (2021) 6500814. [5] N. Hallemans, et al., Best Linear Time-Varying Approximation of a General Class of Nonlinear Time-Varying Systems, IEEE Transactions on Instrumentation and Measurement, 70 (2021) 6503814.

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.

Synthesis and characterization of GA-AgNPs for highly sensitive and selective dual colorimetric detection of thiourea and thiophenol with DFT approach

This work reported a very simple, low cost and easy green method of synthesis of silver nanoparticles (GA-AgNPs) using gallic acid (GA) extracted from Terminalia chebula to detect the soil pollutants thiourea (TU) and thiophenol (TP). The GA-AgNPs were properly characterized by different techniques involving XRD, UV-Visible spectra, XPS, FE-SEM, and Raman spectroscopy. This synthesized GA-AgNPs was used as an effective colorimetric sensor and was even employed in real soil samples. Colorimetric detection was observed in a UV-visible spectrometer by analyzing the change in surface plasmon resonance of NPs when subjected to TU and TP. The result obtained was quick and visibly detectable by the naked eye. The colorimetric study resulted in a good linear relationship and the limit of detection (LoD) was calculated to be 5.79 nM for TU and 0.13 µM for TP. A color detector smartphone application was also used to detect the intensity of color change with variations in different concentrations of TU and TP. This system approach was also applied to real soil samples. Additionally, HPLC was used to validate the presence of TU and TP in the soil and to evaluate their recovery percentage. Density functional theory (DFT) analysis was done to support the plausible mechanism of the interaction between NPs and the sensing molecules. Moreover, the synthesized NPs showed excellent selectivity towards TU and TP in the presence of a wide range of interferences.

In Situ Growth of Nano-MoS2 on Graphite Substrates as Catalysts for Hydrogen Evolution Reaction.

In order to synthesize a high-efficiency catalytic electrode for hydrogen evolution reactions, nano-MoS2 was deposited in situ on the surface of graphite substrates via a one-step hydrothermal method. The effects of the reactant concentration on the microstructure and the electrocatalytic characteristics of the nano-MoS2 catalyst layers were investigated in detail. The study results showed that nano-MoS2 sheets with a thickness of about 10 nm were successfully deposited on the surface of the graphite substrates. The reactant concentration had an important effect on uniform distribution of the catalyst layers. A higher or lower reactant concentration was disadvantageous for the electrochemical performance of the nano-MoS2 catalyst layers. The prepared electrode had the best electrocatalytic activity when the thiourea concentration was 0.10 mol·L-1. The minimum hydrogen evolution reaction overpotential was 196 mV (j = 10 mV·cm-2) and the corresponding Tafel slope was calculated to be 54.1 mV·dec-1. Moreover, the prepared electrode had an excellent cycling stability, and the microstructure and the electrocatalytic properties of the electrode had almost no change after 2000 cycles. The results of the present study are helpful for developing low-cost and efficient electrode material for hydrogen evolution reactions.

Continuous Growth of Carbon Nanotubes on Carbon Fiber Surface by Chemical Vapor Deposition Catalyzed by Cobalt with Thiourea

The continuous preparation of carbon nanotubes (CNTs)/carbon fiber (CF) multiscale reinforcements was realized via one-step chemical vapor deposition (CVD) method. In order to alleviate the damage of CF caused by catalyst etching at high temperature, catalytic promoter was adopted to improve the activity of the catalyst, thus reducing the CVD temperature. By adjusting the cobalt-based catalyst system, the effects of thiourea concentration on the morphology, microstructure and tensile strength of CNTs/CF samples were systematically investigated. It was found that the length and quantity of CNTs were added as the thiourea concentration increased, and the graphitization degree of the sample increased at first because of the well-grown CNTs, and then decreased due to the formation of amorphous carbon. Moreover, the tensile strength of CNTs/CF multiscale reinforcements was improved, which derived from the enhanced defect repair function of synthesized CNTs. Remarkably, CNTs/CF-0.02 exhibited a high single-filament tensile strength value (up to 4.51 GPa), which was about 6.6% higher than that of Desized cf Besides, the crystal structure and composition of reduced catalysts were analyzed, confirming the successful sulfur doping into cobalt particles. Therefore, the work offers a facile, economical, and efficient route for manufacturing CNTs/CF multi-scale reinforcements at comparatively low temperature.

Effect of thiourea concentration on chemical bath deposited CdxZn1 − xS thin films properties for Cu(In,Ga)Se2 solar cells

Effect of thiourea concentration on chemical bath deposited CdxZn1 − xS thin films properties for Cu(In,Ga)Se2 solar cells

Effects of bath parameters on structure characteristic of Ni-W Electrodeposited alloy

This study describes the effects of the bath parameters (temperature, current density, additive concentrations and stirring) on tungsten content and microstructures of Ni-W deposits prepared from thiourea-containing bath, on graphite substrate to protect it from oxidation at high temperature. The morphology of the deposits was studied by optical microscope (TEM) and the approximate composition by energy dispersive spectroscopy (EDS).Increasing the concentration of thiourea refining the structure of the deposits, while the increasing in the current density and temperature led to increase the W content with and without stirring.

INFLUENCE OF THIOUREA CONCENTRATIONS ON GROWTH AND YIELD OF LIGHT PINK LISIANTHUS

An experiment was accomplished in the Horticulture Farm, Sher-e-Bangla Agricultural University, Dhaka, during the period from November 2018 to May 2019 to study the influence of thiourea at different concentration levels on the growth and yield of light pink lisianthus (Eustoma grandiflorum). Thiourea concentrations, viz., C1: 500 ppm, C2: 1000 ppm, and C3: 1500 ppm was used in this experiment, arranged in a randomized complete block design with three replications. Data on growth, physiology, yield, and quality attribute parameters were taken, and all the treatments showed significant variations. Among thiourea concentrations, C3 treatment produced tallest plant (59.6 cm), maximum stem number/plant (4.4), flower/plant (26.6), the highest SPAD value (56.6), the largest flower head diameter (6.3 cm), and the yield/plot (793.2). Overall, thiourea at 1500 ppm concentrations produced the best result and the greatest potential for increasing the Lisianthus flower production.

Effect of Impurity Ions and Additives in Solution of Copper Electrorefining on the Passivation Behavior of Low-Grade Copper Anode

Cu electrorefining using a low-grade copper anode is desirable from the standpoint of electric power savings. Cu electrolysis was carried out in an unagitated sulfate solution with a low-grade copper anode, and the effect of impurity ions and additives in the solution on the passivation of the anode was investigated. The time when anode passivation firstly occurs shortened significantly in a solution containing 0.596 mol·dm−3 of Ni2+ ions as impurity and shortened somewhat in a solution containing As5+(0.053 mol·dm−3) or Bi3+(0.0005 mol·dm−3) ions. Sn2+(0.0004 mol·dm−3) and As3+(0.053 mol·dm−3) ions slightly decreased the time to passivation, but Sb3+(0.004 mol·dm−3) ions did not. The viscosity coefficient of the solution increased when the 0.596 mol·dm−3 of Ni2+ ions were added to the solution, while the diffusion coefficient of Cu2+ ions decreased. The compound of the As–Sb–O or As–Bi–O system was formed in anode slime when the As5+(0.053 mol·dm−3) or Bi3+(0.0005 mol·dm−3) ions were added to the solution, which seemed to increase the compactness of slime. The time to passivation was slightly longer in thiourea-free solution but shortened when the concentration of thiourea was increased from 0.525 to 2.24 mmol·dm−3. The time to passivation was constant in solutions containing 0 to 1.13 mmol·dm−3 of Cl− ions, but significantly decreased as the concentration of Cl− ions increased above 1.13 mmol·dm−3. Cl− ions formed Cu–Cl at the upper area of anode slime, which increased the compactness of slime and promoted the passivation.

Porous 3D columnar-sphere of NiO nanomaterials synthesized for supercapacitors via hydrothermal route: impact of thiourea concentration.

The charge storage application has witnessed a dramatic increase in terms of the short charge-discharge time of supercapacitors, specifically in highly active electrode materials. For charge storage supercapacitor applications, highly porous materials are preferable. In this research article, thiourea acts as a leaving agent in the preparation of the porous 3D spherical architecture of NiO nanomaterials. The influence of the molar concentration of thiourea on structural, morphological, and electrochemical charge storage applications has been studied. X-ray diffraction reveals a cubic structure with Fm3̄m space group for the NiO nanomaterials. The scanning electron microscopy (SEM) images show the porous 3D columnar spherical structure, and FTIR has been used for the optical analysis of the NiO materials. The 1D-3D columnar-spherical structure of the NiO flakes exhibits a high electrochemical charge storage pseudocapacitive nature. The optimized 0.40 M thiourea-NiO (Th-NiO) nanomaterial is highly hydrophilic, exhibiting a maximum specific capacity of 171.1 mA h g-1 at 5 mV s-1 by CV and 148.5 mA h g-1 at 0.2 mA cm-2 by GCD. The highest power, energy densities are 0.96 kW kg-1 and 6.66 W h kg-1 with the highest charge-discharge cycle rating of 92% up to 5000 cycles of the asymmetric NiO//rGO hybrid supercapacitor device.

Inhibition of Aluminium Alloy Corrosion by Thiourea and Lithium Ion in 3.5 % NaCl Solution Using Gravimetric, Adsorption and Theoretical Studies.

The adsorption and inhibition performance of thiourea and lithium ion on aluminium corrosion in 3.5% NaCl were investigated using gravimetric measurement, scanning electron microscope (SEM) analysis and quantum chemical computational techniques respectively. Gravimetric analysis revealed that thiourea has a good inhibitory efficacy of 82% at 1 mM concentration of thiourea on the corrosion inhibition of aluminum under the conditions studied. Also, poor inhibitory effects were recorded with an increase in the concentration of inhibitor, and improvement in inhibition efficiency was observed with the addition of lithium ion. In addition, the effects of temperature (303–333K) on corrosion inhibition was investigated. The findings showed that the effectiveness of the inhibition rises with temperature. The adsorption of thiourea molecules onto an aluminium surface followed the Temkin adsorption isotherm, while the mixed inhibitor of thiourea and lithium ion followed the Langmuir adsorption isotherm model. SEM results confirmed that the inhibition mechanism is due to the formation of a protective thin film on the aluminium surfaces that prevents corrosion. Quantum chemical calculations based on the density functional theory (DFT) revealed that the presence of sulphur and nitrogen in the structure of thiourea molecules is responsible for the strong inhibitory performance due to possible adsorption with Al atoms on the metal surface. The computed experimental and theoretical parameters in this investigation are in good agreement.

Impact of additives on the chemical bath deposition of Zn(O,S) used as buffer layer in high-efficiency Cu(In,Ga)Se2-based solar cells

Cu(In,Ga)Se2-based solar cells achieve highest efficiencies up to 23.4% by using solution-grown Zn(O,S) as the buffer layer. State-of-the-art procedures for Zn(O,S) deposition based on the ammonia-thiourea approach are still characterized by a low growth rate and a high material consumption of reactants. One of the approaches to improve the Zn(O,S) deposition rate is the implementation of compounds leading to a much faster thiourea decomposition and thus to a higher availability of sulfide anions. In this work, we test the impact of oxidative and reductive additives, namely sodium peroxydisulfate Na2S2O8 and hydroxylamine NH2OH, respectively. The Zn(O,S) growth rate could be significantly increased and the consumption of reactants drastically reduced without compromising the performance of fabricated solar cell devices. The composition of the layers was quantified by time-of-flight secondary ion mass spectrometry measurements and the [S]/([S]+[O]) molar ratio was found to vary between 0.65 and 0.85 depending on the thiourea and additive concentration. For cell preparation, in-line co-evaporated Cu(In,Ga)Se2 with RbF post-deposition treatment was used and conversion efficiencies up to 19%, comparable to reference cells with a CdS buffer, could be realized. We discuss the reaction mechanism and conclude for both additives that the resulting sulfide concentration increase evolves via formation of N-hydroxyguanidine intermediates.

A novel and simple naphthol azo dye chemosensor as a naked eye detection tool for highly selective, sensitive and accurate determination of thiourea in tap water, juices and fruit skins

In the present study, a highly accurate and sensitive azo-dye-based colorimetric sensor based on Eriochrome Black T (EBT) was proposed to detect and determine thiourea (TU). TU is truly an important toxic and carcinogenic hazardous pollutant as approved by EPA and IARC. This chemosensor shows a distinct color change from blue to pink during interaction with TU in aqueous medium. So EBT is capable as an applied tool for naked eye detection of TU as its color change is easily observed without any means. The sensing mechanism was also investigated using UV–vis absorption and FT-IR spectra. The linear range and the detection limit of TU sensing were respectively 0.15–18.5 μmol/L and 0.02 μmol/L. In addition, the relative standard deviation (RSD) based on ten repetitions calculated for two different TU concentrations 4.4 and 9.0 μmol/L were 2.3 % and 1.8 %, respectively. Besides its useful application as a naked eye detection tool, the advantages of the developed method include simplicity, elimination of tedious separation and pre-concentration steps, executable in neutral aqueous media, low costs, high accuracy, linear response for wide range of concentrations, low detection limit, high sensitivity, compatibility, and excellent selectivity. The concentration of TU in tap water, fruit juices or fruit skin samples can be visually detected and determined easily using this method. The results showed that EBT is an ideal colorimetric chemosensor for TU, which has been reported for the first time.

Inhibition to dual enzyme-like activities of Ag/CeO2 nanozymes for the detection of thiourea

Although thiourea and its derivatives are applied in medical, food, and chemical industries, sensitive thiourea detection remains a challenging and noticeable topic. Surface-enhanced Raman spectroscopy assay based on an enzyme-inhibition strategy is promising for the detection of thiourea residues. Therefore, in this study, Ag/CeO2 nanomaterials with dual enzyme-Like Activities were synthesized to detection thiourea. We discovered that the Ag/CeO2 nanozymes demonstrated strong peroxidase-like activity and oxidase-like activity, moreover they can accelerate and catalyze 3,3′,5,5′-tetramethylbenzidine enzymatic reaction, with significantly increasing the Raman signal. Instead, once thiourea was introduced into Ag/CeO2 nanozymes, due to the influence of thiourea molecules occupation and nanozymes aggregation, the peroxidase-like activity and oxidase-like activity of Ag/CeO2 decreased sharply, and the colorless substrate 3,3′,5,5′-tetramethylbenzidine would not undergo color changes. Based on this observation, a Raman method for detecting thiourea using oxidized 3,3′,5,5′-tetramethylbenzidine as a probe molecule was developed. The Raman intensity showed a good linearity for the concentration of thiourea in the range of 10−11 M−10−1 M with a correlation coefficient of R2 = 0.9881, and the limit of detection is 2.4 × 10−13 M. Therefore, the proposed Raman mode sensors exhibited excellent selectivity and anti-interference ability which offers a new avenue for exploiting environmental monitoring.

Selective Sorption of Silver Ions from Aqueous Solutions Using Poly(N-thiocarbamoyl‑ 3-aminopropylsilsesquioxane)

The accumulation of electronic waste (e-waste) on the ground leads to environmental pollution with toxic metal ions, which subsequently harms all living organisms. Many countries still use hydrometallurgical or manual methods to extract silver ions from e-waste. These methods are unsustainable and highly toxic; therefore, it becomes necessary to introduce new environmentally compatible methods for separating valuable components from objects of various compositions. This article proposes an environmentally compatible method for the extraction of silver ions from multicomponent systems using poly(N-thiocarbamoyl‑3-aminopropylsilsesquioxane). The sorbent surface was studied by Fourier-transform infrared spectroscopy using an attenuated total internal reflection accessory. The concentration of grafted thiourea groups is 1.39 mmol/g according to elemental analysis. It has been determined that this sorbent is capable of quantitatively extracting silver ions in the pH range from 0 to 6 at a concentration of silver ions in the initial solution of 1·10–4 mol/dm3; the static sorption capacity for silver ions under experimental conditions reaches 1.22 mmol/g. When sorption is carried out in dynamic mode, the value of the dynamic capacity before breakthrough is 0.046 mmol/g, and the value of the total dynamic capacity for silver ions is 0.132 mmol/g. The highest desorption (71–78 %) is achieved using sulfuric acid solutions with a thiourea concentration gradient.

Interactive effect of thiourea application on morphological and physiological characteristics in Cicer arietinum L. grown at different temperatures

Global warming affects many metabolic events in plants and significantly reduces yield and product quality. One of the physiological events most affected by heat stress is nitrogen metabolism. In this study, 5 and 10 mM thiourea was applied to chickpea plants grown at 15, 25, and 35 °C and it was aimed to determine how the plant can cope with heat stress with nitrogen supplementation. It was determined that the root length decreased significantly at all three temperatures depending on the increasing thiourea concentration, while the shoot length increased at 15 and 35 °C compared to the control. There was a decrease in root fresh weight in all three experimental groups due to increasing thiourea concentrations. Only at 5 mM at 15 °C was a highly significant increase seen over the control. When the experimental groups at all temperatures were compared, the highest chlorophyll a, b, and total chlorophyll values were found at 35 °C. It was determined that SOD activity decreased at all three temperatures compared to the control, while CAT and APX activity increased. A significant increase in NR and GS activity was determined in both thiourea treatments at 25 and 35 °C compared to the control.

Highly efficient and fast electrochemical sensor based on aluminium oxide (Al2O3) nanoparticle for the detection of organosulfur compounds

Aluminium oxide (Al 2 O 3 ), otherwise known as alumina, is extensively utilised in various products ranging from electronics, ceramics, thermal, and catalysts. Al 2 O 3 has a number of different phases: γ, η, δ, θ, κ, χ and ρ, with the γ form widely utilised as a catalyst in industrial applications. Although Al 2 O 3 has a wide range of uses, limited studies have been done on detecting organosulfur compounds, such as thiourea (TU), which is an industrial compound that is utilised in chemical and biomedical applications. Therefore, in this study γ-Al 2 O 3 quantum dots (γ-Al 2 O 3 QDs) are used as a sensor material to sense TU in Phosphate Buffered Saline (PBS). The γ-Al 2 O 3 QDs were processed hydrothermally, and the recovered powder was characterised with an X-ray diffraction pattern (XRD), scanning electron (SE) and transmission electron microscopy (TEM) and Fourier transform infra-red spectroscopy (FT IR). The experimental setup had a layer of γ-Al 2 O 3 QDs pasted onto a glassy carbon (GC) electrode and dried in order to make the sensing efficiency of the three electrode system. The γ-Al 2 O 3 QDs/GCE based sensor was tested with very low to high concentrations of TU (3.56, 7.815, 15. 625, 31.25, 62.5, 125, 250, 500, and 1000 μM in PBS) and variable potentials (1 ×10 −2 , 2 ×10 −2 , 3 ×10 −2 , 4 × 10 −2 , 5 ×10 −2 , 6 ×10 −2 , 7 ×10 −2 , 8 ×10 −2 , 9 ×10 −2 , 10 ×10 −2 and 15 ×10 −2 mV/s). The sensor’s sustainability was tested in terms of its cyclic response in longer time periods of one, seven, and thirty days. The electrochemical impedance spectroscopy (EIS) was also analysed, and it showed a number of wide and shallow lines in the high-frequency regions that were used to examine the resistance and conductance of γ-Al 2 O 3 QDs/GCE sensor. In addition to this, a real sample analysis was conducted with γ-Al 2 O 3 QDs/GCE for the tap water samples collected from three different places. The acquired results are then discussed in detail. Graphical representation for sensing of thiourea with γ-Al 2 O 3 QDs/GCE sensor • The γ-Al 2 O 3 QDs were prepared via hydrothermal process and well characterized. • The γ-Al 2 O 3 QDs were employed for the sensing against thiourea at varied conc. • Effect of conc., potential, cyclic responses, impedance and real sample analysis were studied. • Impedance of γ-Al 2 O 3 QDs/GCE were studied with varied thiourea concentrations. • The discussion related to influence with γ-Al 2 O 3 QDs for thiourea was explained.

Physical properties of Cu2MgSnS4 thin films prepared by chemical spray pyrolysis technique: The effect of thiourea concentration

In this work, chemical spray pyrolysis is employed to prepare Cu2MgSnS4 thin films using different concentrations of thiourea (0.14, 0.16, 0.18, 0.20, 0.22, 0.24) M at a substrate temperature of 400 ℃ and thickness of (300±10) nm. The XRD results displayed that all thin films are polycrystalline with tetragonal structure and favorite orientation along the (112) plane. The crystallite size of films is estimated by Scherrer's equation and it was found that it increases with increasing thiourea concentration up to 0.20 M and then it decreases with further increase in thiourea concentration. The FESEM result exhibited the appearance of nanostructures with different particle sizes and shapes. The band gap was estimated using Tauc's relationship and it was found that the value of the band gap increases with increasing thiourea concentration from 1.68 eV at 0.14 M to 1.83 eV at 0.20 M and then it decreases to 1.60 eV at 0.24 M. Raman spectroscopy investigation confirms the purity of the sample formation phase. The main peak for all films is located at about 330 cm-1 . The broadening of this peak in solid solutions can be attributed to the disturbance effects related to the locations of the metal and sulfur atoms in the tetrahedral lattice due to chemical substitutions in the crystalline positions. Hall effect results showed that all films are P-type. The increase in carrier concentration and its motility with increasing thiourea concentrations leads to a decrease in the resistance of the films.

The Effect of Surface-Abundant Hydrogen Bonding on the Electrolyte Reduction for the Stable SEI in Lithium Metal Batteries

Lithium (Li) metal anodes (LMAs) have been attracted world-wide attention as an ideal anode because of its extra-high theoretical capacity (3860 mAh g-1) and low electrode potential (-3.04 V vs S.H.E.). However, the dendritic growth of Li and low Coulombic efficiency (CE) are still hindering their practical uses [1]. To date, numerous methods such as construction of artificial solid electrolyte layer (ASEI) [2], adoption of 3D current collector [3], and tuning of the electrolyte composition [4] have been proposed to prevent Li dendrite growth and increase the CE. Among them, introducing functional additives is one of the most efficient approaches for practical application considering its cost-effectiveness. Until now, various functional additives were introduced to form stable and robust SEI layer in LMBs [4]. Among them, lithium nitrate (LiNO3) is considered as the most efficient electrolyte additive, ensuring high coulombic efficiency (CE) as well as long lifespan of LMBs. When LiNO3 is dissolved in the electrolyte, NO3 - anions are mainly reduced to form inorganic species such as Li3N, which has a high ionic conductivity and mechanical strength. As such species contribute to the construction of the robust and ionic-conductive SEI layer, and hence the reduction of NO3 - is important for stable Li cycling. In this regard, many researchers have focused on increasing reduction of NO3 - by using high-concentration LiNO3 [4], or adding solubilizer to increase more NO3 - in the electrolyte [5]. However, those remedies are still insufficient because most of them increase the viscosity of electrolyte leading to low kinetics, hence a novel and more efficient way to increase NO3 - reduction is needed for practical application.On the other hand, recent researches have reported that the preferential reduction of specific anions is possible by regulation of inner Helmholtz plane (IHP) structure [6]. For instance, Huang et al. reported that intermolecular force between PF6 - anions and surface adsorbent tris(trimethylsilyl) borate could derive in PF6 --abundant IHP, successfully resulted in LiF-rich SEI layer to increase the stability of LMA [6]. Inspired by those works, we expected that NO3 --derived SEI layer would be achieved by using surface adsorbent showing strong intermolecular interaction with NO3 -.In this context, we introduce the adoption of thiourea (TU) as a catalytic additive for the LiNO3 reduction during the SEI formation. Due to its unique molecular structure, addition of TU could induce NO3 - derived SEI layer. Firstly, TU could adsorb onto metallic surface by its S atom. Meanwhile, thiourea could form hydrogen bonding with NO3 - anion by its N-H bonds [7]. Hence in the presence of TU, we suggest that NO3 --abundant electrode surface would be achieved by interaction between TU-NO3 -, resulting in Li3N-rich SEI layer.The adsorption behavior of TU on the Cu electrode was investigated by potential of zero charge (PZC) measurement (Figure 1(a)). As the TU concentration increases, PZC decreases, indicating more surface coverage by TU. Figure 1(b) shows 1H NMR spectra of electrolytes with different components. Upshift displacement of N-H bond of TU were detected after addition of DME and LiTFSI, indicating that intramolecular H-bond of TU were weakened. By contrast, downshift displacement appeared when LiNO3 was added, which means NO3 - would form strong hydrogen bonding with TU. Furthermore, linear scanning voltammetry (LSV) curves at different concentration of TU were measured to investigate the effect of TU on electrolyte reduction (Figure 1(c)). The distinct peaks at 1.6 V and 1.3 V in the cell with 5 wt% LiNO3 indicate reduction of LiNO3 and LiTFSI, respectively. Interestingly, in the presence of TU, negative potential shift and increased current of those redox peaks were shown, indicating that the TU significantly increases the LiNO3 reduction.Importantly, from the XPS analysis, it was found that more abundant Li3N components are in the ASEI layer with TU than that without TU, implying that TU accelerates the reduction of LiNO3 (Figure 2(a-b)). As a result, Li|Cu@ASEI with TU shows better cyclability and higher average CE of 96.44% during 80 cycles compared to Li|Cu@NSEI and Li|Cu@ASEI w/o TU (Figure 3). In addition, morphological and chemical investigation on the favorable ASEI layers assisted by TU, and its electrochemical performance in LMBs will be discussed in this presentation.[1] Cheng et al, Chem. Rev, 117, 10403, 2017.[2] Lopez Jeffrey, et al. JACS 140.37 (2018): 11735-11744.[3] Yang Chun-Peng et al. Nature communications 6.1 (2015): 1-9.[4] Kang et al. Journal of Power Sources 490 (2021): 229504.[5] Zhang et al. Advanced Materials 32.24 (2020): 2001740.[6] Huang et al. Angewandte Chemie. 60.35 (2021): 19232-19240.[7] Nishizawa et al. Tetrahedron letters 36.36 (1995): 6483-6486. Figure 1

Mechanism of Chemical Bath Deposition of CdS Thin Films: Influence of Sulphur Precursor Concentration on Microstructural and Optoelectronic Characterizations

In this study, we aimed to improve our understanding of the response mechanisms associated with the formation of CdS thin films. CdS thin film remains the most valuable option for many researchers, since it has shown to be an effective buffer material for film-based polycrystalline solar cells (CdTe, CIGSe, CZTS). We performed experimental and numerical simulations to investigate the effect of different thiourea concentrations on the characteristics of the CdS buffer layer. The experimental results reveal that an increase in thiourea concentrations had a direct effect on the optical results, with bandgap values ranging from (2.32 to 2.43) eV. XRD analysis confirmed that all deposited films were polycrystalline, except for [1/0.75], where there is no CdS formation. Electrical studies indicated that CdS with a molar ratio of [Cd]/[S] of 1 had the maximum carrier concentration (3.21 × 1014 cm−3) and lowest resistivity (1843.9 Ω·cm). Based on the proposed mechanism, three kinds of mechanisms are involved in the formation of CdS layers. Among them, the ion-by-ion mechanism has a significant effect on the formation of CdS films. Besides, modelling studies reveal that the optic-electrical properties of the buffer layer play a crucial role in influencing the performance of a CIGS solar cell.