Negative Potential Shift Research Articles

Enhancement effect of biomass-derived Carbon Quantum Dots (CQDs) on the performance of Dye-Sensitized Solar Cells (DSSCs)

Corn stover, an agricultural waste, was used to prepare nitrogen self-doped carbon quantum dots (CQDs) through a simple hydrothermal method with only water at near room temperature for the first time. The surface, electrochemical, and photovoltaic characteristics of CQDs doped TiO2 in dye-sensitized solar cells (DSSCs) were thoroughly and systematically examined. The average diameter of blue-fluorescence CQDs measured by a high-resolution transmission electron microscope (HR-TEM) was 4.63 ± 0.87 nm, which consisted of polar functional groups. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy of the biomass-derived CQDs, determined by the cyclic voltammetry (CV) test, were, −5.48 eV and −3.89 eV, respectively. The negative shift of flat band potential (Vfb) in CQDs incorporated photoanode implies the fermi level shifted upward. Experimental results revealed that the improved performance of DSSCs was due to charge transport enhancement and separation, which resulted in the improved energy level configuration between TiO2, CQDs, and electrolytes. In this regard, the CQDs serve as a mediator that enables charge carrier transport without hindrance. In this study, CQDs added to TiO2 + N719, increased short circuit current density (JSC) and power conversion efficiency (PCE) value by ∼26.00 % (10.13 to 12.69 mA/cm2) and 27.20 % (4.78 % to 6.08 %), respectively.

Enhancement mechanism study on the fine hematite flotation by hydrophobic glass microspheres

Previous studies have primarily focused on the use of coarse mineral particles or hydrophobic materials as carriers, whereas this study was the first to investigate the impact of different hydrophobic glass microspheres (HGM-butane, HGM-pentane and HGM-octane) on the flotation behavior of fine hematite, and it revealed the interaction mechanism through Zeta potential and flotation kinetics analysis. The results of micro-flotation tests indicated that the addition of HGM-pentane can increase the flotation recovery of fine hematite from 65.27 % to 84.64 %, which was significantly better than using the collector NaOL alone. Zeta potential results showed that the incorporation of HGM-pentane caused a further negative shift in the surface potential of hematite, enhancing its adsorption capacity with bubbles. Flotation kinetics analysis demonstrated that the addition of HGM-pentane increased the flotation kinetic constant, promoting the flotation rate of fine hematite. This study revealed that the interaction between hydrophobic glass microspheres and fine hematite was primarily through hydrophobic forces and electrostatic attraction, forming a hematite-HGM complex, which in turn improved the flotation recovery of fine hematite. This provided a theoretical basis for the development of efficient flotation reagents and offers new insights into the efficient utilization of fine hematite.

Cathodic shift in flatband potential of hematite based photoelectrodes: Evaluating and correlating the redshift to solar driven photocatalysis

As a promising metal oxide semi-conductor, hematite (α-Fe2O3) has interesting optical properties to be regarded as photoactive material. In this study, we evaluated the cathodic shift in onset potential (Eonset) and the negative shift in flat band potential (Efb). It was observed that the Eonset value of −0.457 V for α-Fe2O3 based electrode shifted to −0.638 V for the ternary nanocomposite (PNFC) [Pani/Ni-α-Fe2O3/CNT] based electrode. The flat band potential for α-Fe2O3 in 1 M NaOH is at −0.49 V which shifts to −0.68 V for the ternary nanocomposite (PNFC). This photoelectrochemical enhancement appears due to electron-hole pair separation. Therefore, it apparently increases the photocurrent trace for PNFC at −0.60 V to 7.04 mA cm-2, compared to the photocurrent of 4.52 mA cm-2 observed for pristine α-Fe2O3. According to the Mott-Schottky plot, the donor concentration (Nd) for the α-Fe2O3 is 4.83 × 109 cm-3, whereas for the ternary nanocomposite (PNFC) is 7.68 × 109 cm-3, respectively. As evident, the Nd value increase for the ternary nanocomposite PNFC points to the proximity of the Fermi (Ef) level below the CB edge when Ni doped α-Fe2O3 comes in contact with polyaniline (Pani). Indeed, the ternary nanocomposite PNFC with lower Eg value (1.32 eV) and higher photocurrent (7.04 mA cm-2) show higher photo-activity with percent degradation of 98.42 % for photocatalytic degradation of Sunset Yellow under visible light irradiation. The aforementioned correlations of the energetic levels of band edges with the shifting of Efb to more negative potentials provide insight into the high photo-activity observed.

Poly-methionine/graphitic carbon nitride modified screen-printed electrodes: A metal-free, bio-interface for tryptophan sensing

Tryptophan (TRP) is an essential amino acid needed for the growth and proper functioning of the human body. A balanced intake of TRP-rich food products is essential to meet the daily requirements. As both low and high levels of TRP are associated with clinical disorders, an optimum amount of TRP intake is critical. Hence, developing a method to efficiently detect TRP in food and nutritional supplements is essential. Accordingly, this study reports the electrochemical detection of TRP using poly-methionine/graphitic carbon nitride modified screen-printed electrode (gCN.Meth|SPE). To our knowledge, this study is the first attempt to decipher the electrodeposition of gCN.Meth on a conducting substrate through a systematic analysis of the electro-functionalized gCN.Meth surface using XRD, FT-IR, HR-SEM, EDX, and AFM. The synergistic benefits of both the gCN and conducting poly(methionine) resulted in augmented electrochemical performance exhibiting a pronounced TRP oxidation peak in both cyclic voltammetry (CV) and square wave voltammetry (SWV). The improved electrochemical response can be ascribed to the specific interactions between the TRP and gCN through π- π interactions and hydrogen bonding and electrostatic interaction between TRP and methionine. This facilitated interaction resulted in the electro-catalytic oxidation of TRP with a negative potential shift of 0.126 V and a 16.6-fold increase in the current response compared to unmodified SPE. The gCN.Meth|SPE exhibited a 25.12 times higher sensitivity compared to bare SPE, with a linear response in the concentration ranges of 1.0–300.0 μM and a low detection limit of 29.9 nM. The interference study further indicated that gCN.Meth-modified SPEs is highly effective for the precise and reliable detection of tryptophan in real samples.

Hybrid Overlayer of Defective Ni-MOF and NiO Nanoparticles toward Efficient TiO2/CdS Type-II Heterojunction.

The severe photocorrosion of cadmium sulfide (CdS) restricts its practical application for solar hydrogen production. Although remarkable progress has been achieved with an overlayer strategy for isolating the CdS surface, the lifetime of CdS-based photoanodes is still far from the actual requirements. Herein, a hybrid overlayer of defective Ni-MOF and NiO nanoparticles has been developed through the chemical bath deposition method with postannealing. This hybrid overlayer of Ni-MOF-d is coated on the surface of the TiO2/CdS type-II heterojunction. The composite photoanode exhibits a photocurrent density of 4.41 mA cm-2 at 1.23 VRHE, which is 3.47- and 1.32-fold that of CdS and TiO2/CdS, respectively. The Ni-MOF-d overlayer gives rise to a negative shift of the onset potential by 59.51 mV. After a long-term stability test of 11 h, a photocurrent retention of 70% is observed, which is among the most robust CdS-based photoanodes. The kinetics studies reveal that the performance improvements can be attributed to the multiple functions of the Ni-MOF-d hybrid overlayer, including isolating the CdS surface from the electrolyte, cocatalyzing the electrode oxidation processes, passivating the surface defect states of CdS, and facilitating the charge injection from the photoanode to the electrolyte.

Creating electron traps in BiOBr nanosheet arrays by bulk-phase F doping to restrain carrier recombination for efficient photoelectrochemical water splitting system

Bismuth oxide semiconductors in the field of photoelectrochemical (PEC) water splitting face the problems of narrow photo response range and fast carrier compounding. On the basis of the above problems, we used a solvothermal method to prepare BiOBr nanosheet arrays (NSAs), which have a special structure that facilitates carrier transport. Subsequently, the F element was introduced into the bulk phase of BiOBr using a simple hydrothermal method. The results show that the BiOBr-F photoelectrode exhibits excellent photoelectrocatalysis performance under light and bias voltage. The photocurrent density of the BiOBr-F photoelectrode reached 28.35 μA cm−2 at 1.23 V vs. RHE, which is 2.01 times higher than that of the pure BiOBr, while a negative shift of the onset potential of 119 mV was obtained. The optical absorption tests show that the introduction of the F element forms an impurity energy level thereby extending the optical absorption range of BiOBr. Photoluminescence tests reveal that the introduction of F element effectively restricts the electron-hole pair recombination. This is due tothe fact that the F atoms replace some of the O atoms in BiOBr to create electron traps, thus forming a large number of electron-rich regions in the structure, which in turn reduces the electron-hole pair recombination. This work provides an effective solution to reduce the recombination between carriers by creating electron traps in semiconductor materials through bulk phase doping.

(Invited) Photocatalytic H2 Evolution Activity of Anisotropic-Shaped ZnSe-AgInSe2 Solid Solution Quantum Dots with a Near-IR-Responsivity

Semiconductor nanocrystals, often referred to as quantum dots (QDs), exhibit unique physicochemical properties due to the quantum size effect when their size is less than 10 nm. In our previous works, we successfully synthesized Zn-Ag-In-S (ZAIS) solid solution QDs with a tunable energy gap (Eg) and then reported the photocatalytic activity for H2 evolution depending on their morphology and particle composition [1,2]. However, ZAIS QDs have limited light absorption with wavelengths less than ca. 600 nm, restricting their utilization of near-infrared light in solar light. In this study, we report the preparation of near-IR-responsive QD photocatalysts with use of Zn-Ag-In-Se (ZAISe) solid solution semiconductors. Precise controls over their morphology and particle composition enabled to vary their photocatalytic H2 evolution activity.ZAISe QDs with different compositions and particle shapes (sphere or rod) were synthesized by thermal decomposition of corresponding metal acetates and selenourea in a mixture solution of oleylamine and dodecane thiol at 250 oC. The chemical composition of QDs was controlled by varying the Zn fraction in metal precursors, ensuring nearly stoichiometric composition.The obtained QDs with a rod shape had lengths varying from ca. 10 to 100 nm, correlating with an increase in the Zn fraction. The onset wavelengths of absorption spectra of the ZAISe QDs were red-shifted from 500 nm to 900 nm with decreasing Zn fraction, indicating that the Eg of ZAISe QDs was controlled between visible and near-infrared wavelength regions.The QDs modified with dodecane thiol showed poor dispersibility in water and almost no photocatalytic activity for H2 evolution. In contrast, the surface modification of QDs with 3-mercaptopropionic acid enabled to uniformly disperse in an aqueous solution. The photocatalytic activity of ZAISe QDs was investigated for H2 evolution as a model reaction. The irradiation to ZAISe QDs in an aqueous solution containing Na2S and Na2SO3 as hole scavengers was carried out using Xe lamp light (λ> 350 nm). The H2 evolution rate exhibited a remarkable dependence on both the composition and particle shape of ZAISe QDs. The photocatalytic activity showed a tendency to increase with the enlargement of the Eg of QDs, probably due to the negative shift of conduction band minimum potential. The optimum H2 evolution activity was obtained with rod-shaped QDs having the Eg of 1.65 eV, being twice as large as that of spherical QDs with a similar Eg. This behavior can be attributed to the change of the crystal facets exposed on the QD surface. References Kameyama, T. Takahashi, T. Machida, Y. Kamiya, T. Yamamoto, S. Kuwabata, and T. Torimoto, J. Phys. Chem. C, 2015, 119, 24740-24749.Torimoto, Y. Kamiya, T. Kameyama, H. Nishi, T. Uematsu, S. Kuwabata, and T. Shibayama, ACS Appl. Mater. Interfaces 2016 , 8, 27151-27161.

Electrochemical and Spectroscopic Investigations of Bismuth(III) Pharmaceuticals with L-Glutathione

Due to the importance of L-cysteine in the human system, the interaction of metals with this amino acid are worthy of investigation by various methods. In this laboratory1, we have investigated the interaction of bismuth(III) compounds with L-cysteine by both cyclic voltammetry and UV-VIS spectroscopy in an attempt to understand the role of bismuth in treating gastrointestinal maladies.2 The addition of bismuth(III) compounds to solutions of L-cysteine causes a negative potential shift for bismuth(III) reduction as an indication of complex formation between bismuth(III) and L-cysteine. This interaction is also evident by the appearance of a UV-VIS spectroscopic band at 340 nm (Bi-sulfur bond). Even at low pH values (pH 1.0), electrochemical studies show evidence of some kind of interaction even when there is no 340 nm band. These investigations have been conducted at pH 1.00 and 3.00 to simulate conditions in the human stomach and at pH 7.40 MOPS [(3-N-morpholino)propanesulfonic acid] to simulate general physiological conditions, in particular the intestinal tract. Recent work has involved extension of this work to L-glutathione, a tripeptide incorporating L-cysteine, under similar conditions. As might be expected, these interactions are considerably more complicated than those involving L-cysteine. As an example, there is a considerable positive potential shift for the reduction of bismuth(III) citrate in the presence of L-glutathione on the first and second voltammetric sweeps at gold and glassy carbon electrodes. This behavior evidently reflects the rather long (several seconds) time required for the re-formation of the bismuth complex with L-glutathione after its reductive ligand (L-glutathione) loss during bismuth(III) reduction on the first sweep. In addition, there is evidence of a film buildup on the electrode surface as observed by peak current increases during multiple potential sweeps. These observations are planned for inclusion in this symposium presentation.References T. Cheek and D. Peña, J. Electrochem. Soc., 167, 155522 (2020)Li, R. Wang, and H. Sun, Acc. Chem. Res., 52, 216 (2019).

Effect of Citrate-Based Bath pH on Properties of Electrodeposited Cu–Zn Coating on an Aluminum Substrate

In this study, Cu–Zn alloys were deposited in citrate-based electrolytes on aluminum substrate by electrodeposition method. The effect of bath pH variation on the properties of the obtained Cu–Zn alloy coatings was investigated. The electrochemical behavior of the citrate-based baths and the crystalline structure, surface morphology and elemental content, electrical resistivity and thermal behavior of the alloy coatings were analyzed. According to the results of cyclic voltammetry (CV) analysis, increasing bath pH caused a negative shift in the cathodic deposition potential. In addition, the anodic dissolution peaks first shifted to the positive side with increasing pH and then shifted back to the negative direction. According to the results of XRD analysis, the phase structure of Cu–Zn alloys generally consists of α and β′ phases, but according to differential scanning calorimeter (DSC) analysis, it is possible that there is a γ phase in the structure in addition to these phases. In addition, pH increase (4.5 to 6.5) caused a relative increase in crystal grain size (~14 to ~ 25 nm). The Zn content of Cu–Zn coatings first increased (~pct 15 to ~ pct 55) with pH increase, then followed a horizontal trend (~pct 55 to ~ pct 59) with further pH increase and then exhibited a slight decreasing trend (~pct 59 to ~ pct 52). The pH increase significantly affected the surface morphology of the coatings and denser coatings were obtained with increasing pH. While the electrical resistivity of Cu–Zn coatings first increased (0.0408 to 0.0696 µΩcm for 297 K) with increasing pH, it tended to decrease (0.0696 to 0.0479 µΩcm for 297 K) again at higher pH values. In addition, the electrical resistivity of the coatings increased with increasing measurement temperature. According to DSC analysis of the coatings, endothermic peaks were obtained, possibly representing the transformation from γ to β′ phase.Graphical

Designing nanoporous Pd catalyst with dual enhancement of thermodynamics and kinetics for formic acid oxidation reaction

Conventional strategies for developing highly efficient electrocatalysts involve enhancing thermodynamics to minimize overpotential and improving kinetics to maximize reaction current. However, current research on Pd-based catalysts for formic acid oxidation reaction (FAOR) mainly focuses on accelerating its kinetics to increase the peak current. This study proposes a catalyst design that can simultaneously improve the kinetics and thermodynamics of FAOR. Specifically, the home-made catalyst (NPG-Pt1-Pd1) is obtained by sequentially depositing monolayer Pt and Pd shells on the surface of nanoporous gold (NPG) substrate. Compared with commercial Pd/C, this electrocatalyst exhibits a noticeable negative shift in onset potential (∼100 mV) and a significantly improved peak current (∼6 times). Experimental data and theoretical calculations demonstrate that NPG-Pt1-Pd1 exhibits a comparatively suitable adsorption energy for small molecules, not only reducing the overpotential but also accelerating the reaction rate of FAOR. Moreover, when applied in direct formic acid fuel cells (DFAFC), the NPG-Pt1-Pd1 anode with an exceptionally low Pd loading of 8.5 μg cm−2, achieves a remarkable power density of 141 mW cm−2. The power efficiency of Pd is 230 times that of Pd/C (1 mg cm−2, 73 mW cm−2). Therefore, this work provides a new methodology for developing efficient Pd-based FAOR electrocatalysts.

Chiral Effect on the Electrochemistry of Magnetic Ferrite Colloidal Nanocrystal Assembly Modified by Amino Acids.

Chirality on the molecular or nanometer scale is particularly significant in chemistry, materials science, and biomedicine. Chiral electrochemical reactions on solid surfaces are currently a hot research topic. Herein, a chiral solid surface is constructed in aqueous solutions by mixing chiral molecules, d- and l-glutamic, with γ-Fe2O3 and Fe3O4 nanoparticles (NPs) and MnFe2O4 colloidal nanocrystal assembly (CNA). Cyclic voltammetry and differential pulse voltammetry measurements are conducted in a phosphate buffer solution (PBS) containing ascorbic acid (AA) or isoascorbic acid (IAA), and a chiral effect appears on the electroreduction of ferric ions of amino acid-modified magnetic samples. A negative or positive potential shift is observed, respectively, for magnetic structures modified by l- and d-glutamic acid in aqueous AA electrolyte, while the opposite is observed for these samples in IAA electrolyte. The reduction peak current increases by 0.8-1.2 times for the electrodes modified with l- and d-glutamate molecules, improving the electron transport efficiency. The chiral effect is absent when the electrolytes contain achiral uric acid or dopamine, or even chiral l-/d-/ld-tartaric acid. The chiral recognition between d-/l-glutamic acid and AA/IAA at the electrochemical interface is suggested to be related to their spinal configurations. These observations will be helpful for the rational design of inorganic functional chiral micro/nanostructures.

One-Step Electrodeposition of MnO2-Graphitic Carbon Nitride Composite Layer on Screen Printed Electrode for Electrocatalytic Dopamine Sensing

Electroanalysis using screen-printed electrodes offers a cost-effective, rapid, and on-site analyte quantification. Nevertheless, ensuring the necessary stability, sensitivity, and selectivity of SPE in order to perform precise ultra-low-level analyses is critical. The use of nano-structured materials for surface functionalization is one of the most prevalent strategy to augment the sensitivity and selectivity of sensors. However, the selection of the surface functionalization technique and material plays a crucial role. The present study outlines a single step electro-functionalization of the screen-printed sensor (SPE) with a carbon–metal oxide composite consisting of graphitic carbon nitride and manganese oxide (gCN.MnxOy). The electrodeposited gCN.MnO2 layer has been thoroughly analysed using spectroscopic, microscopic, and electrochemical techniques. As a test case, the electro-functionalized SPE was used to quantify dopamine by monitoring its electrocatalytic oxidation. Due to π-π interaction between the aromatic ring structures of the gCN and dopamine molecules, H-bonding, enhanced electroactive site, and facilitated charge transfer at the MnO2.gCN surface layer, the modified SPEexhibited a 15-fold higher peak current and a negative potential shift of 150 mV for DA oxidation. Being 44 times more sensitive, gCN.MnO2|SPE exhibited a detection limit of 10 nM compared to 5.36 µM for the unmodified electrode. As proof of application, the gCN.MnO2|SPE successfully estimated dopamine in pharmaceutical formulations, banana peel, and clinical samples namely saliva, urine and blood serum with an error of less than 9 %. We believe, the proposed modification protocol has the potential to create low-cost disposable functional interfaces that match the desirable properties of commercial products.

Cavitation erosion-corrosion properties of as-cast TC4 and LPBF TC4 in 0.6 mol/L NaCl solution: A comparison investigation

In this work study, a comparative analysis was undertaken to investigate investigation into the cavitation erosion (CE) and corrosion behavior of laser powder bed fusion (LPBF) TC4 and as-cast TC4 in 0.6 mol/L NaCl solution. Relevant results indicated that LPBF TC4 revealed a rectangular checkerboard-like pattern with a more refined grain size compared to as-cast TC4. Meanwhile, LPBF TC4 surpassed its as-cast counterpart in CE resistance, demonstrating approximately 2.25 times lower cumulative mass loss after 8 h CE. The corrosion potential under alternating CE and quiescence conditions demonstrated that both LPBF TC4 and as-cast TC4 underwent a rapid potential decrease at the initial stages of CE, while a consistent negative shift in corrosion potential was observed with the continuously increasing CE time, indicative of a gradual decline in repassivation ability. The initial surge in corrosion potential during the early CE stages was primarily attributed to accelerated oxygen transfer. As CE progressed, the significant reduction in corrosion potential for both LPBF TC4 and as-cast TC4 was attributed to the breakdown of the passive film. The refined and uniform microstructure in LPBF TC4 effectively suppresses both crack formation and propagation, underscoring the potential of LPBF technology in enhancing the CE resistance of titanium alloys. This work can provide important insights into developing high-quality, reliable, and sustainable CE-resistant materials via LPBF technology.

Study on electrodeposition of gallium-selenium binary alloy films from Deep Eutectic Solvent

Ga-Se alloy coatings were successfully electrodeposited at different deposition potentials from Deep Eutectic Solvent (choline chloride-ethylene glycol). The co-deposition mechanism of Ga and Se was investigated through cyclic voltammetry (CV) and chronoamperometry (CA). The results indicate that the co-deposition of Ga and Se occurs through an induced co-deposition mechanism, with Se deposition taking place initially, followed by the induced deposition of Ga. Furthermore, the Ga-Se co-deposition process was analyzed with the Scharifker-Hills model. The research results indicate that with the negative shift of the deposition potential, the Ga-Se co-deposition process gradually transitions from diffusion-controlled three-dimensional progressive nucleation and growth to three-dimensional instantaneous nucleation and growth.Characterization of the surface morphology and composition of the obtained coatings at different potentials was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results reveal that with the negative shift of the deposition potential, the morphology of the coating transforms from spherical to granular, and as the deposition potential continues to decrease, the granules further refine. Simultaneously, with the negative shift of the deposition potential, the relative content of Ga in the coating increases, while the relative content of Se decreases. The Ga-Se alloy coatings before and after annealing were characterized by X-ray diffraction spectroscopy (XRD). The results indicate that, after annealing, the coating exhibits the phase of GaSe. Besides, the optical and electrical properties of the annealed Ga-Se alloy coating were investigated by UV–visible spectroscopy and photoelectrochemical techniques. The results demonstrate that the coating exhibits excellent optical and electrical characteristics, with a photocurrent response of 0.014 mA/cm2, a bandgap of 1.98 eV, and p-type conductivity.

Optimized porous nanostructure of carbon fibers enabling excellent stability of Pt-based catalysts for oxygen reduction reaction

Facile synthesis of highly-dispersed Pt-based electrocatalysts on porous carbon supports with strong durability is extremely desirable for oxygen reduction reaction but remains challenging. The influence of pores in carbon supports on the stability and activity of catalysts is ambiguous and needs to be elucidated. Targeting this aim, herein, we prepared a series of carbon nanofibers with tunable pore diameter and specific surface area using the resorcinol-formaldehyde (RF) resins as a model system. Homogeneous composite precursors composed of RF resins and silica colloids were synthesized by the surfactant-assisted simultaneous polycondensation of RF resins and tetraethylorthosilicate (TEOS). The diameter of the pores induced by removal of silica could be controllable tailored through thermal treatment of the composite under various target temperatures. Pt3Co alloy nanoparticles loaded on the as-synthesized porous carbon nanofibers were prepared by an optimized wet-impregnation method. The experimental results indicated that the carbon nanofibers with pore size distribution focused on ∼1.27 nm and ∼2.34 nm provided the best stability without limiting current density decay, and negative shift of half-wave potential (E1/2) and mass activity (MA) loss of Pt after 20000 potential cycles are relatively mild. Conversely, negative shift of 21 mV, 15 mV and 22 mV in E1/2 and mass activity loss of 51.8%, 30.2% and 33.0% were observed for the Pt3Co nanoparticles supported on MC-60, MC-100 and MC-140 matrices which have pore size distribution focused on ∼2.73 nm, ∼2.73 nm as well as ∼4.66 nm, and ∼4.66 nm, respectively. This work demonstrates the importance of micropores and small mesopores for activity and long-term stability enhancement of carbon supported Pt-based electrocatalysts.

Electrochemical study on under-deposit corrosion evolution of oil pipelines

In the development of oil and gas fields, due to the sand, calcium, and magnesium ions in the produced liquid, the under-deposit corrosion formed by deposition during the transportation process has become one of the key factors of pipeline failure. Therefore, aiming at the problem of CaCO3 under-deposit corrosion in CO2-flooded oil pipelines, this paper studied the influence of deposit thickness change on metal corrosion based on electrochemical experiments, image characterization, and corrosion product analysis. The results showed that the corrosion process of the deposit layer can be divided into three stages. (1) The deposit layer promoted the movement of the electrolyte and then enhanced the corrosion rate of the matrix, leading to the increase of the size and maximum pit depth of the matrix, which was manifested as a rapid negative shift of the open circuit potential. (2) The deposit layer played a certain physical shielding role, leading to the size and maximum pit depth of the pit decreasing, and the number of pits increasing, at which the open circuit potential basically remained unchanged. (3) The deposit layer can play an effective physical shielding role, and the oxygen concentration corrosion inside and outside the deposit layer made the number of pits increase sharply, which was manifested as a slow negative shift of open circuit potential. The deposit layer mainly affected the cathode reaction process of the corrosion process. With the increase of the deposit thickness, the metal corrosion intensified with an increasing corrosion current density.

Effect of cathodic polarizations on the failure behavior of epoxy coating/low alloy steel systems under high hydrostatic pressure

Failure behavior of epoxy coating/low alloy steel systems applied with cathodic polarization at 0.1 MPa and 15 MPa was investigated based on a deep−sea environment simulation test device. The results showed that the diffusion of water into the coating was significantly accelerated by the high hydrostatic pressure under the same polarization potential, and the time of water uptake of the coating that reached saturation was shortened; the coating's physical structure was significantly affected by the high hydrostatic pressure; the generation of highly conductive Fe3O4 was promoted in the corrosion products, which accelerated the metal corrosion process. Under the same hydrostatic pressure, with the negative shift of the polarization potential, the coating protective performance was significantly reduced and metal corrosion was mitigated to a certain extent; the water transport behavior showed a tendency to shorten the time of water uptake of the coating that reached saturation and lengthen the duration of the saturation state, which may be related to a more severe degree of cathodic delamination and the increase of water consumption for cathodic reactions under the coating. In addition, the increase of the weakly conductive α−Fe2O3 content in the corrosion products may cause a reduction in the cathodic protection current at the same polarization potential, resulting in the reduction of the protection effect on the metal.

Enhanced photovoltaic performance of dye sensitized solar cells using cesium bromide modified TiO2 electron transport layer

TiO2 is one of the most widely explored materials as an electron transport layer (ETL) in dye sensitized solar cells (DSSCs) due to its excellent physical and chemical properties. However, recombination at the device's interface slackens the charge carrier movement, adversely affecting their device performance. Rapid extraction of photogenerated charge carriers plays a vital role in developing high efficiency DSSCs. The conduction band alignment of TiO2 ETL and N719 dye light absorber plays a crucial role in charge carrier dynamics of DSSCs. Herein, the band structure of TiO2 ETL is finely tuned by the incorporation of cesium bromide (CsBr). At the optimal concentration (0.4 Wt. %), DSSCs achieved the best power conversion efficiency (PCE) of 9.28 % compared to 7.61 % for pristine TiO2. The modified TiO2–CsBr ETL induced a negative shift in flat band potential (Vfb) from −0.46 to −0.50 V, which improved the open circuit voltage (VOC), its work function (ɸ) from −4.71 to −3.75 eV and increased conduction band minimum (CBM) from −3.58 to −2.42 eV. CsBr incorporation increased electron density in TiO2 matrix, indicating the suppression of trap state and significantly improved the overall photovoltaic performance of DSSCs.

Assessment of the electrostatic binding of ferrocenylmethyl-nitroaniline derivatives to DNA: A combined experimental and theoretical study

The present study investigates the electrostatic binding interactions between ferrocenylmethylnitroaniline derivatives and DNA using a combination of experimental and theoretical approaches. The objective is to elucidate the binding mechanisms and evaluate the potential of these derivatives as DNA-targeting agents. Experimental techniques, including cyclic voltammetry (CV) and UV–Vis spectroscopy (UV–Vis), were employed to assess the binding affinity and conformational changes in DNA upon interaction with the derivatives. Our findings reveal that the ferrocenylmethylnitroaniline derivatives exhibit strong electrostatic interactions with DNA, as confirmed by the negative formal potential shift observed in CV. The binding constants and free binding energies obtained from the docking simulation were found to be consistent with those obtained from CV and UV–Vis spectral analysis. Furthermore, the binding site size was determined from the voltametric data. Complementary theoretical calculations such as geometry optimization, MEP analysis, Mulliken charge distribution, and HOMO-LUMO surface were performed by DFT approach (B3LYP/aug-cc-pVTZ/6-311++G (d,p)) to gain insights into the structural data, active regions, and chemical reactivity of derivatives. Molecular docking simulation verifies that electrostatic attraction plays a fundamental role in the interaction of Fc2N, Fc3N, and Fc4N with DNA. The molecular dynamics simulations elucidated the stability of DNA-ligand complexes formed with Fc2N, Fc3N, and Fc4N compounds. Analysis of root mean square deviation (RMSD) and radius of gyration (Rg) indicated stable binding and maintained compactness of DNA structures, underscoring the robustness of these interactions for potential therapeutic applications.Top of Form

Mechanistic analysis and validation of an efficient novel inhibitor for scheelite and calcite flotation separation: A DFT and MD simulation study

Due to the similar surface characteristics of scheelite and calcium-bearing minerals, the efficient utilization of scheelite has become a current research focus. This study investigated a novel inhibitor, phosphonic carboxylic acid copolymer (POCA), and explored its influence on the flotation separation of scheelite and calcite in a sodium oleate collector system. The flotation experiments demonstrated that 3 mg/L POCA can effectively inhibit the flotation of calcite. The results of zeta potential and Fourier transform infrared spectroscopy (FTIR) indicate the emergence of a novel carboxyl (C = O) characteristic peak in the infrared spectrum of calcite following the introduction of POCA. This suggests that the interaction between POCA and the calcite surface occurs via chemical adsorption. Additionally, a markedly negative shift in the surface potential of calcite is observed, suggesting that this interaction is more robust compared to the interaction with scheelite. Density functional theory (DFT) and molecular dynamics (MD) simulations suggest that POCA can chemically adsorb onto the Ca site on the calcite surface through the –SO3H and –PO3H2 functional groups, simultaneously enhancing the hydrophilicity of the calcite surface to a certain degree.