Cyclic Voltammetry Measurements Research Articles

Experimental and computational study on antioxidant activity and molecular properties of novel ferrocenyl Schiff bases

In this study, antioxidant and molecular properties of some important novel ferrocenyl Schiff bases were studied. The 4-Ferrocenyl aniline synthetic pathway was chosen as the general procedure for the synthesis of Schiff bases. Two experimental techniques, UV–Visible spectroscopy and cyclic voltammetry, and one theoretical DFT method was employed to find out their antioxidant activity and molecular properties of some novel ferrocenyl Schiff bases and compared it with standard antioxidant (Ascorbic acid). Maximum wavelength, extinction coefficient, IC30 and IC50 were estimated by using UV–Visible spectroscopy. For theoretical investigations, computational Amsterdam density function software was employed to study the molecular properties and reaction parameters based on density functional theory calculations. The cyclic voltammetry (CV) measurements in electrochemical experiments were done at room temperature while diffusion coefficient was estimated by using CV graphs. UV–Vis spectra of these compounds exhibited similar peaks with greater intensity ranges from 312 nm to 314 nm and smaller intensity ranges 471 nm to 473 nm which occurred because of the only substituent R (naphthoxy, phenoxy and phenoxy) in these compounds. Registered Amsterdam density function was utilized to determine the optimized structure, FTIR spectra, UV–Visible spectra, HOMO, LUMO, dipole moment, ionization potential, electron affinity, band gap, hardness, chemical potential and electrophility index. The overall electrode processes were found to be diffusion controlled and the novel compounds showed appreciable antioxidant activities.

Activation flotation of lime-depressed pyrite with carbon dioxide: Performances, mechanism and pilot-scale application

Activation flotation of lime-depressed pyrite by sulfuric acid (H2SO4) is usually accompanied by safety hazards and environmental pollution. Exploring eco-friendly, economical and effective activator to replace H2SO4 holds great significance for the sustainable development of mining industry. In this study, carbon dioxide (CO2) as a potential activator was applied in activation flotation of lime-depressed pyrite. Micro-flotation experiments results showed CO2 significantly improved the floatability of pyrite, and a maximum recovery of 93.94% was achieved under optimal operating conditions. The activation mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated the depression of pyrite by lime was attributed to the formation of iron oxide/hydroxide species and calcium film, and CO2 effectively eliminated these hydrophilic compounds from the surface of pyrite, thus promoted the adsorption of xanthate onto the pyrite surface. Moreover, the anodic oxidation of xanthate on pyrite and the influence of CO2 on this process were investigated by cyclic voltammetry measurements. It was found that xanthate oxidation to form dixanthogen was more likely to occur in the presence of CO2, and this reaction replaced pyrite surface oxidation as the dominant anodic process. Finally, pilot-scale experiments were successfully conducted and the recovery of pyrite reached 93.18%, surpassing the ore dressing index of using H2SO4 as activator in actual production at the same period. Moreover, the concentration of sulfate ions in mineral processing wastewater was significantly reduced, and the annual cost of activator can be saved by 0.52 million RMB. The new process of activation flotation pyrite with CO2 has prospects for large-scale application in terms of activation performance, cost-effectiveness and environmental impact.

MnO@Mn2O3 nanocrystals embedded in biochar networks for sustainable anode of lithium-ion batteries

MnO is an alternative for commercial graphite as anode material for lithium-ion batteries (LIBs), if the issue of unstable performance caused by volume changes, poor conductivity, and changes in valence state of Mn is addressed. In this study, a series of nano MnO/biochar-containing composite materials were prepared with Mn(NO3)2, urea and pomelo peel as raw materials, via simple hydrothermal treatment and calcination, as anode materials for LIBs, where the biochar was used as inexpensive conductive medium and volume buffer. The electrochemical performance of the composite materials shows complicated correlation with the biochar contents, which associate with different carbonization temperatures. Elaborate characterizations with XRD, SEM, TEM, and Mn 2p, Mn 3s XPS spectra were conducted and jointly analyzed, which revealed that the surface of MnO nanocrystals undergoes different degrees of oxidation. The thickness of the surface amorphous Mn2O3 layer on the MnO nanocrystals influences the long-term electrochemical stability more significantly than the circumstances of biochar encapsulation, which was proved through cyclic voltammetry (CV) measurements. A composite material with moderate biochar content and thin layer of Mn2O3 coating on MnO nanocrystals will show more stable electrochemical performance. Based on this principle, one regulated composite material (MnOx/BC-650) gives an ultra-stable capacity of 446.9 mAh∙g−1 at 500 mA∙g−1 after 200 cycles. This study provides new insight for both revealing the true structure of manganese oxides and developing long-term stable MnO-containing anode materials for LIBs.

Activated carbon synthesized from Jack wood biochar for high performing biomass derived composite double layer supercapacitors

In this study, the electrochemical properties of bioderived activated carbon-based electrodes for supercapacitors formed using a sintered ceramic binder were investigated. Activated carbon derived from Jack wood tree (Artocarpus heterophyllus) with variable amounts of TiO2 nanoparticles as a binder, were used as electrodes in order to get good, activated carbon films on FTO substrates. No other binders were used in this study since most conventional binders devastate the electrical conductivity in the films. Furthermore, TiO2 has higher temperature tolerance compared to polymeric binders thus the electrode prepared can be used in wider applications. A series of electrochemical double-layer capacitors were fabricated and characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The supercapacitors prepared showed double-layer capacitive behavior. The electrodes that contain 90 % activated carbon and 10 % TiO2 show optimum performance along with an impressive specific capacitance of 147 F g−1 at 2 mV s−1 scan rate. This supercapacitor exhibits a power density of 68.5 W kg−1 while the energy density is 8.02 Wh kg−1. When the power density is as high as 1186.51 W kg−1 the energy density drops to 5.71 Wh kg−1. According to cyclic voltammetry measurements taken for 1000 cycles, the supercapacitor shows excellent cycle stability without any traces of capacitance drop.

Effective polysulfide control in lithium–sulfur batteries utilizing BiFeO3 nanoparticles

Lithium–sulfur batteries (LiSBs) offer high energy density, cost-effectiveness, and eco-friendliness, making them promising for future energy storage. This study explores using BiFeO3 (BFO) nanoparticles (NPs) to tackle challenges such as lithium polysulfides (LiPs) and shuttle issues in LiSBs. It employs a solid-state melt diffusion technique, encapsulates sulfur in single-walled carbon nanotubes (SCNTs), and utilizes BFO for effective polysulfide control. Herein, composite cathodes of sulfur (S)/SCNTs (abbr. SCNT) were fabricated, and cells were designed using a BFO-coated separator (SCNT-BFS). In addition, a cathode modification was performed with composite S/SCNTs/BFO (SCNT-BF), and a comparative analysis was conducted to assess the effectiveness of the BFO in the separator and the cathode. Cyclic voltammetry measurements revealed that the increased current peak intensity at lower reduction potential in SCNT-BF and SCNT-BFS indicated control of higher-order LiPs (Li2Sx, where 4 ≤ x ≤ 8), resulting in the generation of more stable lower-order products (Li2S2/Li2S). The charge/discharge analysis revealed controlled LiPs, resulting in high-capacity retention in SCNT-BF (∼75%) and SCNT-BFS (∼88%) over 200 cycles, which yielded capacities of 526 and 700 mAh/g at C/8 (1C = 1675 mA/g). These promising results suggest that incorporating BFO into the cathode and separator can advance the commercialization of durable LiSBs.

The influence of phosphine ligands on the redox properties of 1,4-divinylanthrylene-bridged diruthenium complexes and a derived macrocyclic analog

We report on a series of dinuclear 1,4-divinylanthrylene-bridged diruthenium complexes 1A-Ru-PR3 with different phosphine ligands (PiPr3, PiPr2Me, PPh3, and PMe3) and with coordination numbers of five or six. All compounds were characterized by NMR spectroscopy, high resolution ESI-MS and, in the case of 1A-Ru-PiPr3 and 1A-Ru-PMe3, single crystal X-ray diffraction. Cyclic voltammetry measurements reveal that the PR3 ligands, besides tuning the redox potentials, exert a strong influence on the stability of their one- and two-electron oxidized forms. Information on the charge- and spin-density distribution was obtained by IR, UV/Vis/NIR and EPR spectroscopy. Our results indicate full charge and spin delocalization in 1A-Ru-PiPr3•+, 1A-Ru-PMe3•+ and macrocyclic, isophthalate-bridged 2A-Ru-PiPr2Me••2+, whereas 1A-Ru-PiPr2Me•+ constitutes a peculiar case, where valence-delocalized and valence-localized structures seem to coexist.

Transport properties of mechanochemically synthesized copper (I) selenide for potential applications in energy conversion and storage

This work studied the thermal stability, electrical, and thermoelectrical properties of copper(I) selenide, Cu2Se synthesized by high-energy milling in a planetary ball mill. The phase composition was investigated by X-ray powder diffraction analysis and scanning electron microscopy. The conversion of the precursors during mechanochemical synthesis and the stability of the product was monitored by thermal analysis. The dependence of electrical properties on the product porosity was observed. For the densification of Cu2Se, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric characterization. High-temperature thermoelectric properties of synthetic Cu2Se were compared to its natural analogue-mineral berzelianite in terms of its potential application in energy conversion. Based on the results a relatively high figure-of-merit, ZT parameter (~ 1.15, T = 770 K) was obtained for undoped Cu2Se, prepared by rapid mechanochemical reaction (5 min). Cyclic voltammetry measurements of Na/NaClO4/Cu2Se cell implied that mechanochemically synthesized Cu2Se could be used as a promising intercalation electrode for sodium-ion batteries.

Co-Ni co-sputter deposited bimetallic thin film catalysts for alkaline hydrogen and oxygen evolution reactions

Co-Ni bi-metallic thin films with different stoichiometries have been deposited by magnetron co-sputtering technique on Ni foam (NF), Si and carbon paper substrates. The structural and morphological characterisations of these films have been done by X-ray diffraction, X-ray absorption spectroscopy and Field Emission Scanning Electron Microscope measurements. The performances of these films for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been evaluated through electrochemical measurements like Linear Sweep Voltammetry, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy measurements. Operando X ray absorption near edge spectroscopy measurements have also been carried out during HER and OER to decipher the redox reaction mechanisms. It has been observed that the HER and OER performance of all the Co Ni bi-metallic thin films on NF are found to be better than that of bare NF. The CoNi sample with composition of 58.7 % Co and 41.3 % Ni shows the best catalytic activity and stability towards HER and OER reactions. Though the HER activity is not the best but is comparable to many results reported in the literature, however the catalyst shows excellent OER activity with overpotential of 214 mV for 10 mA/cm2 current density. This is much better than that of the OER benchmark catalyst RuO2 and most of those reported in the literature. The OER is kinetically slower than HER and requires more overpotential, hence a significant improvement in the catalytic OER activity will definitely enhance the overall water splitting activity and hydrogen production efficiency. Thus the Co-Ni bi-metallic catalyst prepared by an easily scalable and highly reproducible magnetron co-sputtering technique has significant potential to emerge out as a technologically viable water splitting catalyst.

Palladium/coconut husk biochar composite material as an effective electrocatalyst for ethanol oxidation reaction

This study utilised coconut husk biochar as an alternative sustainable carbon support for Pd-based electrocatalyst for ethanol oxidation reaction in basic medium. Coconut husk biochar (BC) was prepared via slow pyrolysis at 800 °C for 1 h at a ramp rate of 5 °C min−1. The Pd/BC catalyst was prepared via borohydride-facilitated reduction of palladium chloride solution. TEM analysis revealed good dispersion of the Pd nanoparticles on the biochar support with particle size ranging from 1.9 to 3.4 nm. Cyclic voltammetry (CV) measurements of Pd/BC in 1.0 M ethanol in 0.1 M KOH gave an on-set potential of −0.615 V (versus Ag/AgCl) with a forward peak current density of 23.87 mA cm−2, which is slightly higher than the commercial Pd/C catalyst. The Pd/BC also has a higher electrochemical stability and durability than the commercial Pd/C catalyst based on chronoamperometry studies (i.e., 44.43% versus 39.64% current retention). The synthesised coconut husk biochar–supported Pd catalyst exhibited promising results for ethanol oxidation reaction for alkaline direct ethanol fuel cell application.

Sr and Fe substituted LaCoO3 nano perovskites: Electrochemical energy storage and sensing applications

Perovskite-type LaCoO3 (LCO), La0.8Sr0.2CoO3 (LSCO), and La0.8Sr0.2Co0.9Fe0.1O3 (LSCFO) were prepared though a sol gel assisted hydrothermal method for supercapacitors and electrochemical sensors for heavy metal ions detection applications. Rhombohedral crystal structure was confirmed using experimental and DFT based computational XRD pattern. LCO, LSCO and LSCFO based modified carbon paste electrodes were prepared for cyclic voltammetry, electrochemical impedance spectra and galvanostatic charge discharge measurements. Among all electrodes, LSCFO results with 715.5 Fg−1 specific capacitance with 97 % retention after 1500 cycles. Cyclic voltammetry measurements for the sensing and detection of heavy metal ions (chromium and mercury) were carried out using all three electrodes and observed that LSCFO showed better response comparatively to that of other two electrodes, thus can be claimed as a potential mixed metal oxide nanomaterial for the fabrication of electrodes for storage of energy and sensor applications.

Ornated hydrangea-like M-MO/graphitic porous carbon derived via direct carbonization of MOFs for electrooxidation of methanol in alkaline DMFC

Due to their low operating temperature, ease of storage, transportation, and low greenhouse gas emissions, direct methanol fuel cells (DMFC) are considered the best choice of fuel cells for energy conversion. Although its theoretical thermodynamic energy conversion efficiency is ~97 %, its achievable energy conversion efficiency is still in the range of 30–40 %. To improve the reaction kinetics, it is important to look for an electrocatalyst with low cost and high efficiency. In the present study, direct carbonization of [Ni, Cu, and (Ni/Cu)] metal-organic framework (MOF) was carried out under a nitrogen gas flow at 800 °C for 2.5 h, where the MOF precursor was completely converted into graphitic porous carbon well ornamented with Metal/Metal oxides (M/MO). The as-prepared nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectric spectroscopy (XPS), Fourier transform infrared (FTIR), and the Brunauer–Emmett–Teller technique (BET). The prepared materials were used as electrocatalysts in a methanol oxidation reaction solution in an alkaline solution. The cyclic voltammetry (CV) measurements for Ni-MOF, Cu-MOF, (Ni/Cu) MOF, Ni-MOF800, Cu-MOF800, and (Ni/Cu)MOF800 showed excellent current densities of 17, 1.05, 44.25, 30, 11.56, and 53 mA∙cm−2, respectively at 0.6 V with a scan rate of 50 mV∙s−1. Whereas, the retention percent value is (96.2 %) for Ni-MOF, (93.1 %) for (Ni/Cu) MOF800, (96.7 %) for (Ni/Cu) MOF, (87.5 %) for Ni-MOF800, (97 %) for Cu-MOF, and (50.2 %) for Cu-MOF800 after an hour. Since M/MO/C800 demonstrated remarkable catalytic activity in relation to methanol oxidation and an abundance of cheap value, it is regarded as a promising candidate for future electrooxidation catalysis of MeOH in direct methanol fuel cells (DMFCs).

Poly (aniline-co-aniline-2,5-disulfonic acid) / L-ascorbic acid / Ag@SiO2 / polysafranin nanocomposite: synthesis, characterization and anomalous electrical behaviour.

We report the synthesis of sulfonated copolyaniline/polysafranin/L-ascorbic acid/Ag@SiO2 fine powdered nanocomposites and investigate the influence of incorporating the dye on their conductivity. The composite was characterized via IR, UV, cyclic voltammetry (CV), electric, dielectric, SEM, TEM, TGA and DSC measurements. Microscopy images revealed intensified spherical particles that were dispersed across the entire surface, and the SiO2/Ag particles were distributed on the surface. The XRD results exhibited peaks at many 2q values, and their interatomic spacing (d) and crystallite (grain) sizes were calculated. The thermal degradation curves exhibited an interesting model of stability. The cyclic voltammogram exhibited redox peaks identical to those of the reported analogues. The d.c. conductivity of the oligomer varied from 0.06 - 0.016 (s/cm), and that of the composite varied from 0.008 to 0.016 (s/cm). The material changed from a semiconductor to a metallic material. The observed conductivity is mainly attributed to self-doping between the sulfonate groups and the charged nitrogen atoms in the polymer chains. The frequency dependence of the permittivity, ε', showed a marked effect on the frequency window under consideration. The permittivity, ε', is independent of the increase in the frequency of the oligomer and the composite. This behavior supports the non-Debye dependency by confirming the occurrence of electrode polarization and space charge effects. In conclusion, the incorporation of safranin dye with a thermally stable, highly sulfonated polyaniline derivative/Ag@SO2 nanocomposite achieved improved conductivity after heating. The d.c. conductivities are comparable to those of many commercial inorganic or organic composites, and because of their attractive electrical properties, we suggest that these materials are promising for electronic field applications.

Electrochemically polymerized dopamine activated carbon paste sensor for selective and sensitive detection of rutin in the presence of riboflavin

In this work, a sensor was developed for the quantification of RT in food and medicine samples using electro-polymerization of dopamine (DA) on the surface of a carbon paste electrode in 0.2 M phosphate buffered saline (PBS) of 7.0 pH by cyclic voltammetry (CV). The surface properties of bare carbon paste electrode (BCPE) and poly (DA) modified carbon paste electrode (PDAMCPE) were studied using scanning electron microscopy (SEM), electrochemical impedance study (EIS), and CV techniques. Two electron two proton transfer process was seen during the electrochemical reaction of RT with adsorption-controlled process. Under optimum conditions, the peak current increased linearly with an increase in RT concentration for CV in the range of 0.4 to 2.0 μM and differential pulse voltammetry (DPV) in the range of 0.4 to 2.5 μM and the limit of detection (LOD) was found to be 0.0045 μΜ and for CV and 0.079 μM for DPV techniques respectively. Even in the presence of some interferents like organic compounds and metal ions, the developed electrode exhibits good anti-interference ability for RT, and good selectivity was obtained for RT in the presence of riboflavin (RF). The developed sensor presents good stability, repeatability, and reproducibility. The CV measurement was performed for the analysis of RT in real samples such as green tea and medicine samples which showed a good recovery and this work has been not reported previously.

Silicon-tin thin-film anodes for low and high power-density lithium-ion batteries

Silicon (Si) is a promising replacement material for graphite, the commonly utilized anode material in lithium-ion batteries (LIBs). Si has a theoretical specific capacity up to 11 times higher than that of graphite. However, pure Si has two main issues: high electronic resistivity and significant volume change during charge/discharge cycling. To overcome these issues, Si was alloyed with high-conductivity materials. In this contribution, physical vapor deposition was utilized to produce binderless silicon-tin anodes for LIBs. Tin is a lithium-active alloying material that has high electrical conductivity and high specific capacity (i.e., up to three times that of graphite). Electronic resistivity, residual film stress, X-ray photoelectron spectroscopy, Raman spectroscopy, and cyclic voltammetry measurements were performed to thoroughly analyze the deposited Si-Sn films and help understand their charge/discharge cycling performance at low and high C-rates. At a low C-rate of 0.5 C, the alloyed films did not show any improvement compared to pure Si. However, the alloyed films showed better performance compared to pure Si when tested at a high C-rate of 10 C. Si-Sn films with (40 – 50 wt.% Sn) were able to retain a specific capacity of around 680 mAh g−1 after 1000 cycles.

Novel, compact electrochemical and impedance instrumentation

This paper presents the development of a novel, compact electrochemical and impedance instrumentation utilizing an analog integrated circuit (IC) for biosensing applications. Given the increasing availability of multifunctional integrated circuits (ICs), there is a growing need for devices capable of versatile applications spanning multiple fields. To address this requirement, a design was tailored to accommodate multifunctional techniques for biosensing. By combining multi-layer printed circuit board (PCB) techniques with 3D printing, the module was compact and capable of cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) measurements. Additionally, a comparison was conducted between the CV functionality of a commercial and the customized module. The results demonstrated that the customized module outperformed the commercial module. The Bode and Nyquist plots obtained from the EIS measurements accurately depicted the impedance values of resistance (R) and capacitance (C) in basic RC circuits. The experimental results show the error of R was below 2% and C was below 4% across the full frequency range from 500 Hz to 10 kHz. Furthermore, the high performance of this system was demonstrated by its successful application in monitoring the ripeness of bananas through EIS measurements. These measurements specified the total impedance and phase to assess the ripening stages accurately. This suggests the potential of the proposed system for utilizing impedance measurements in controlling fruit quality. Based on the achieved results, the proposed system holds promise for various electrochemical research and monitoring applications, particularly for electrochemical sensors and biosensors.

Novel Au/Cu2NiSnS4 Nano-Heterostructure: Synthesis, Structure, Heterojunction Band Offset and Alignment, and Interfacial Charge Transfer Dynamics.

Considering the importance of physics and chemistry at material interfaces, we have explored the coupling of multinary chalcogenide semiconductor Cu2NiSnS4 nanoparticles (CNTS NPs) for the first time with the noble metal (Au) to form Au-CNTS nano-heterostructures (NHSs). The Au-CNTS NHSs is synthesized by a simple facile hot injection method. Synergistic experimental and theoretical approaches are employed to characterize the structural, optical, and electrical properties of the Au-CNTS NHSs. The absorption spectra demonstrate enhanced and broadened optical absorption in the ultraviolet-visible-near-infrared (UV-Vis-NIR) region, which is corroborated by cyclic voltammetry (CV) readings. CV measurements show type II staggered band alignment, with a conduction band offset (CBO) of 0.21 and 0.23 eV at the Au-CNTS/CdS and CNTS/CdS interface, respectively. Complementary first-principles density functional theory (DFT) calculations predict the formation of a stable Au-CNTS NHSs, with the Au nanoparticle transferring its electrons to the CNTS. Moreover, our interface analysis using ultrafast transient absorption experiments demonstrate that the Au-CNTS NHSs facilitates efficient transport and separation of photoexcited charge carriers when compared to pristine CNTS. The transient measurements further reveal a plasmonic electronic transfer from the Au nanoparticle to CNTS. Our advanced analysis and findings will prompt investigations into new functional materials and their photo/electrocatalysis and optoelectronic device applications in the future.

The Divalent Lanthanoid Triflates Ln(CF3SO3)2(CH3CN) (Ln=Sm, Eu): Structure, Luminescence, and Magnetism.

The reaction of the trivalent lanthanoide triflates Ln(OTf)3 (Ln=Sm, Eu; OTf=CF3SO3 -) with the respective metals in acetonitrile leads to the Ln(II)-triflates Eu(OTf)2(CH3CN) (monoclinic, P21/n, Z=4, a=1053.54(1), b=610.28(5), c=1946.92(2) pm, β =98.611(4)) and Sm(OTf)2(CH3CN) (monoclinic, P21/n, Z=4, a=1054.41(4), b=612.16(2), c=1952.65(7) pm, β =98.524(2)). The isotypic strontium compound Sr(OTf)2(CH3CN) (monoclinic, P21/n, Z=4, a=1056.39(5), b=610.05(3), c=1950.1(1) pm, β =98.900(2)°) has been obtained from SrCO3 and triflic acid. The compounds have been investigated by X-ray diffraction, vibrational spectroscopy, luminescence spectroscopy, cyclic voltammetry, thermal analysis, and magnetic measurements.

Gradient OH Desorption Facilitating Alkaline Hydrogen Evolution Over Ultrafine Quinary Nanoalloy

AbstractStrengthening OH adsorption on electrocatalyst is crucial to promote the rate‐determining water dissociation step of alkaline hydrogen evolution reaction (HER), whereas too‐intensified OH adsorption will poison the active sites instead. This dilemma remains one of the major challenges for improving the electrocatalysts’ alkaline HER activities. Herein, a surprising finding that the strongly adsorbed OH on an ultrafine quinary PtCoCuNiZn nanoalloy can be facilely desorbed via a unique gradient OH desorption pattern is reported, which tremendously boosts its alkaline HER activity. Theoretical simulations unravel that the ultrafine PtCoCuNiZn nanoalloy possesses versatile metal sites for adsorbing OH and the strongly adsorbed OH can be gradiently transferred to desorb from the ultrafine PtCoCuNiZn nanoalloy with moderate energy barriers for each transfer step that is the gradient OH desorption. In the meanwhile, the unique gradient OH desorption mode on the ultrafine PtCoCuNiZn nanoalloy is also experimentally evidenced by the in situ Raman spectroscopy and cyclic voltammetry measurements. This finding offers a fresh opportunity to expedite the alkaline HER without compromising the OH adsorption strength on electrocatalysts, which thus maximally promotes their water dissociation properties and unlocks the full potential of their alkaline HER activities.

Extraction and characterization of natural dye from leaves of Lannea coromandelica and application on cotton fabric

Purpose The purpose of this study is to extract and characterize a novel natural dye from the leaves of Lannea coromandelica and the extraction with finding ways of dyeing cotton fabric using three mordants. Design/methodology/approach The colouring agents were extracted from the leaves of Lannea coromandelica using an aqueous extraction method. The extract was characterized using analysis methods of pH, gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) and cyclic voltammetry measurement. The extract was applied to cotton fabric samples using a non-mordant and three mordants under the two mordanting methods. The dyeing performance of the extracted colouring agent was evaluated using colour fastness properties, colour strength (K/S) and colour space (CIE Lab). Findings The aqueous dye extract showed reddish-brown colour, and its pH was 5.94. The GC-MS analysis revealed that the dye extract from the leaves of Lannea coromandelica contained active chemical compounds. The UV-vis and FTIR analyses found that groups influenced the reddish-brown colour of the dye extraction. The cyclic voltammetry measurements discovered the electrochemical properties of the dye extraction. The mordanted fabric samples showed better colour fastness properties than the non-mordanted fabric sample. The K/S and CIE Lab results indicate that the cotton fabric samples dyed with mordants showed more significant dye affinities than non-mordanted fabric samples. Originality/value Researchers have never discovered that the Lannea coromandelica leaf extract is a natural dye for cotton fabric dyeing. The findings of this study showed that natural dyes extracted from Lannea coromandelica leaf could be an efficient colouring agent for use in cotton fabric.

Studies of the Functionalized α-Hydroxy-p-Quinone Imine Derivatives Stabilized by Intramolecular Hydrogen Bond.

In this work, reactions between 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-diones with different benzohydrazides were studied. Nucleophilic substitution at C(6) was followed by isomerization and led to α-hydroxy-p-quinone imine derivatives. Synthesized compounds represent a combination of several structural motifs: a benzimidazole core fused with α-hydroxy-p-quinone imine, which contains a benzamide fragment. X-ray crystallography analysis revealed the formation of dimers linked through OH···O interactions and stabilization of the imine form by strong intramolecular NH···N hydrogen bonds. The protonation/deprotonation processes were investigated in a solution using UV-Vis spectroscopy and a 1H NMR titration experiment. Additionally, the electrochemical properties of 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-dione and its α-hydroxy-p-quinone imine derivative as cathode materials were investigated in acidic and neutral environments using cyclic voltammetry measurements. Cathode material based on 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-dione could act as a potentially effective active electrode in aqueous electrolyte batteries; however, further optimization is required.