Good Charge Transfer Research Articles

Amorphous mesoporous sulfur-rich 1T/2H-MoS2 nanospheres as high-capacity cathode materials for advanced magnesium ion batteries

Two-dimensional layered-structure MoS2 has been explored as the promising cathode materials for magnesium ion batteries benefited by its wide layer distance and satisfactory capacity. However, such strong interaction between Mg2+ and MoS2 brings about the sluggish diffusion kinetics and irreversible electrochemical reaction, leading to a decreased specific capacity and poor rate capability. How to adopt its structure engineering and interface engineering to boost the Mg2+ diffusion kinetics and enhance the electrochemical reversibility of MoS2 is still a huge challenge. Herein, the amorphous sulfur-rich 1T/2H-MoS2 mesoporous nanospheres (a-MoS2+x, 0<x<1) have been developed via a facile one-pot hydrothermal route. Acted as a cathode material for magnesium ion batteries, owing to the cooperate effects of inherent rich active sites, high conductivity and wide layer distance induced by the coexistence of sulfur-rich, 1T phase and nearly amorphous features, the as-prepared a-MoS2+x demonstrates an ultra-high discharge capacity (438.7 mAh g−1 for 50 cycles at 0.1 A g−1), promising rate capability (97.6 mAh g−1 at 1.0 A g−1), and good cyclic stability (110 cycles at 0.5 A g−1), superior to the crystalline MoS2 (c-MoS2) and other previously reported MoS2 counterparts. Besides, the kinetics results indicate that the a-MoS2+x manifests good charge transfer and diffusion kinetics, and its entire charge storage is a combination of surface-controlled capacitance behavior and diffusion-controlled battery behavior. Moreover, some ex-situ Raman, XPS and HRTEM characterization techniques are employed to disclose the Mg2+ storage mechanism. Such remarkable magnesium storage properties of a-MoS2+x demonstrates its promising application as cathode for magnesium ion batteries.

Insights into the structural, dielectric, optical and electrochemical characteristics reveal the limiting parameters toward efficient OER catalysts in the perovskite solid solution Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8)

Due to their structural stability and flexibility, perovskite oxides have paved their way as oxygen evolution reaction (OER) electrocatalysts. The in-depth understanding of the limiting factors toward good activity and fast charge transfer are still considered as major challenges for highly active OER perovskite catalysts. In this work, we disclose the changes in the perovskite structure and properties that influence the activity as we introduce new criteria to be considered for perovskites electrocatalysts design. The activity test of the series Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8) reveals the overpotential of 300 mV @ 10 mA.cm−1, and Tafel slop of 57.6 mV dec−1, as the lowest values corresponding to the composition x = 0.4. As function of the composition, the dielectric constant is found to decrease from 3000 (x = 0.2) to 953 (x = 0.4), and increases up to 5497 (x = 0.8). This variation of the dielectric constant is found to influence the activity of the catalysts where lowest overpotential of 300 mV @ 10 mA.cm−1 is found for x = 0.4 with the smallest dielectric constant. The phase transition detected in the perovskite series upon substitution has induced a distortion in the unit cell, which is found to be in alignment with the evolution of the overpotential in the perovskites series. The distortion has induced a preferable octahedra orientation for efficient OER reaction, this orientation correspond to the interatomic distance <Ti/Fe-O2> (1) = 1.89 Å and <Ti/Fe-O2> (2) = 2.04 Å (x=0.4) with the condition of <Ti/Fe-O2> (1) remains shorter than <Ti/Fe-O2> (2). The band gap, thus the conduction and valence bands edges, is found to decrease with the increase of the interatomic distance (Fe/Ti-O) and with the deviation of the Bond angle (B)-O2-(B) from the ideal value of 180°. These findings put light on the limiting factors of the perovskites activity by linking the structural parameters and the physical properties with the objective of accurately designing highly-efficient perovskite OER electrocatalysts.

Investigation of G-Quadruplex DNA-Mediated Charge Transport for Exploring DNA Oxidative Damage in Telomeres.

The human telomeric DNA 3' single-stranded overhang comprises tandem repeats of the sequence d(TTAGGG), which can fold into the stable secondary structure G-quadruplex (G4) and is susceptible to oxidative damage due to the enrichment of G bases. 8-Oxoguanine (8-oxoG) formed in telomeric DNA destabilizes G4 secondary structures and then inhibits telomere functions such as the binding of G4 proteins and the regulation of the length of telomeres. In this work, we developed a G4-DNA self-assembled monolayer electrochemical sensing interface using copper-free click chemistry based on the reaction of dibenzocyclooctyl with azide, resulting in a high yield of DNA tethers with order and homogeneity surfaces, that is more suitable for G-quadruplex DNA charge transport (CT) research. At high DNA coverage density surfaces, G-quadruplex DNA is 4 times more conductive than double-stranded DNA owing to the well-stacked aromatic rings of G-quartets acting as good charge transfer channels. The effect of telomeric oxidative damage on G-quadruplex-mediated CT is investigated. The accommodation of 8-oxoG at G sites originally in the syn or anti conformation around the glycosyl bond in the nonsubstituted hTel G-quadruplex causes structural perturbation and a conformational shift, which disrupts the π-stack, affecting the charge transfer and attenuating the electrochemical signal. The current intensity was found to correlate with the amount of 8-oxodG, and the detection limit was estimated to be approximately one lesion in 286 DNA bases, which can be converted into 64.7 fmol on the basis of the total surface DNA coverage. The improved G4-DNA order and homogeneity sensing interface represent a major step forward in this regard, providing a reliable and controlled electrochemical platform for the accurate measurement and diagnosis of G4-DNA oxidative damage.

Synthesis of nickel-sphere coated Ni-Mn layer for efficient electrochemical detection of urea

Using a trustworthy electrochemical sensor in the detection of urea in real blood samples received a great attention these days. A thin layer of nickel-coated nickel-manganese (Ni@NiMn) is electrodeposited on a glassy carbon electrode (GC) (Ni@NiMn/GC) surface and used to construct the electrochemical sensor for urea detection. Whereas, electrodeposition is considered as strong technique for the controllable synthesis of nanoparticles. Thus, X-ray diffraction (XRD), atomic force microscope (AFM), and scanning electron microscope (SEM) techniques were used to characterize the produced electrode. AFM and SEM pictures revealed additional details about the surface morphology, which revealed a homogenous and smooth coating. Furthermore, electrochemical research was carried out in alkaline medium utilizing various electrochemical methods, including cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The electrochemical investigations showed that the electrode had good performance, high stability and effective charge transfer capabilities. The structural, morphological, and electrochemical characteristics of Ni@NiMn/GC electrodes were well understood using the analytical and electrochemical techniques. The electrode showed a limit of detection (LOD) equal to 0.0187 µM and a linear range of detection of 1.0–10 mM of urea. Furthermore, real blood samples were used to examine the efficiency of the prepared sensor. Otherwise, the anti-interfering ability of the modified catalyst was examined toward various interfering species.

Highly efficient electrocatalytic water oxidation based on non-precious metal oxides/sulfides derived from a FeCoNi-metal organic framework

One of the main challenges for oxygen evolution reaction (OER) is to develop electrocatalysts with high performance, suitable stability, and low cost. First-row transition metal compounds have received attention due to their high electrocatalytic activity and diverse electronic structure. Meanwhile, metal-organic frameworks (MOFs) have emerged as promising alternative for OER due to their porous structure and unsaturated metal sites. In this study, FeCoNi-MOF based on MIL-88B was synthesized by a hydrothermal method. Then, the performance of the catalyst was investigated and improved by calcination and sulfidation at three temperatures of 250 ℃, 350 ℃, and 450 ℃. The phase development and crystal structure parameters of the synthesized samples were confirmed through X-ray diffraction. Additionally, the intensity of the peaks increased with the rise in calcination temperature. Field emission scanning electron microscopy revealed well-defined and uniformly distributed nanorods and nanospheres particles of calcinated and sulfides samples. The weight percentage (wt%) of the elements in the samples were verified to align with their stoichiometric ratios. The synthesized catalysts were loaded onto a nickel foam by a one-step method, and their electrocatalytic properties were examined in the OER process in 1.0 M KOH alkaline solution. The (FeCoNi)-O250 ℃ electrocatalyst, maintaining its nanorod morphology, exhibited an overpotential of 313 mV at a current density of 10 mA.cm-² and a small, stable Tafel slope of 31.5 mV.dec−1 and good charge transfer of 0.73 mF. Cm−2. However, the (FeCoNi)-S250 ℃ electrocatalyst showed better performance in the OER process with an overpotential of 298 mV at a current density of 10 mA.cm-² and a small and stable Tafel slope of 29 mV.dec−1 and good charge transfer of 0.82 mF. Cm−2. In other words, a higher Cdl increased reaction rates or lower overpotentials required for the reaction to occur. Furthermore, the activity of this catalyst remained constant at a fixed current density of 10 mA.cm-² for 18 hours. Based on the electron microscopy observations, and electrochemical evaluations, this superior performance can be attributed to the morphological change from nanorods to porous nanospheres due to sulfidation, resulting in increased electrochemically active sites and decreased charge transfer resistance.

Evaluation of innovative fluroapatite /silicon dioxide modified zirconia nanocomposites coated on Ti–13Nb–13Zr alloy for dental implant application

Dental implants are intended to function as a durable method for replacing missing teeth. A biocompatible dental alloy is used to achieve integration with the jawbone through Osseointegration. This creates a strong base for the implant, allowing it to withstand the mechanical forces generated during biting and chewing. Dental alloys are commonly subjected to various mouth conditions known for their intricate corrosion potential. Corrosion can weaken the structural integrity of the implant, causing issues such as implant loosening, micro-motion at the implant-bone contact, implant fracture, allergic reactions, toxicity, and possible disruption of the Osseo integration process. To improve the alloy's corrosion resistance and biocompatibility, its surface can be altered using nanocomposite materials. The materials provide a protective coating to the alloy, creating a physical barrier that effectively prevents corrosive substances from reaching the underlying bulk material. This study involves modifying the surface of the dental alloy Ti–13Nb–13Zr with Fluroapatite (FAP)/Silicon dioxide (SiO2) modified zirconia (ZrO2) nano composites. The altered surfaces are then studied in simulated body fluid and artificial saliva solutions using in vitro methods. The FAP/SiO2 modified ZrO2 nanocomposites is applied onto a Ti–13Nb–13Zr alloy utilizing Electrophoretic deposition and Dip coating techniques. The coated samples were analysis utilizing FTIR, XRD, and SEM with EDS. Corrosion analysis was carried out on coated and uncoated samples using Electrochemical methods in simulated body fluid and artificial saliva solution. The biocompatibility is assessed using MTT assay, contact angle, and immersion testing in both SBF and Artificial saliva. EIS and corrosion study results show that FAP/SiO2 modified ZrO2 nanocomposites coated Ti13Nb13Zr alloy has high polarization resistance, low corrosion rate, and good charge transfer resistance, indicating excellent corrosion resistance. The contact angle study showed that the surface-modified Ti13Nb13Zr alloy is superhydrophilic, increasing implant surface osseointegration. Cell viability measurements reveal good cell growth, while immersion investigations show calcification, leading to enhanced osseointegration between the implant and its surrounding tissues. hence, it is an excellent material for dental implants application.

Carbon Nanotubes as a Solid-State Electron Mediator for Visible-Light-Driven Z-Scheme Overall Water Splitting.

So-called Z-scheme systems, which typically comprise an H2 evolution photocatalyst (HEP), an O2 evolution photocatalyst (OEP), and an electron mediator, represent a promising approach to solar hydrogen production via photocatalytic overall water splitting (OWS). The electron mediator transferring photogenerated charges between the HEP and OEP governs the performance of such systems. However, existing electron mediators suffer from low stability, corrosiveness to the photocatalysts, and parasitic light absorption. In the present work, carbon nanotubes (CNTs) were shown to function as an effective solid-state electron mediator in a Z-scheme OWS system. Based on the high stability and good charge transfer characteristics of CNTs, this system exhibited superior OWS performance compared with other systems using more common electron mediators. The as-constructed system evolved stoichiometric amounts of H2 and O2 at near-ambient pressure with a solar-to-hydrogen energy conversion efficiency of 0.15%. The OWS reaction was also promoted in the case that this CNT-based Z-scheme system was immobilized on a substrate. Hence, CNTs are a viable electron mediator material for large-scale Z-scheme OWS systems.

Perovskite materials advance the potent sensor exploration

AbstractPerovskite materials with unique crystal structure have developed rapidly in recent years owing to their special physical and chemical properties, such as high light absorption and extraordinary electrocatalytic properties. Metal halide perovskites are quite attractive in various fields because of their simple manufacturing process, adjustable band gap, good charge transfer performance, and high theoretical photoelectric conversion efficiency. Therefore, perovskite oxides mixed with metal elements become ideal samples for studying the surface and catalytic performance of catalysts. In this review, various metal perovskites are clearly classified and introduced according to the corresponding synthesis methods, including hydrothermal method, sol–gel method, and high‐temperature solid phase, as well as coprecipitation. The excellent properties of perovskite make it extensively used in nanotechnology, chemistry, environmental protection, and material science, especially in solar cells and sensors. In particular, the nanosized perovskite materials are becoming more and more popular in sensors, which was reviewed in detail here. Most importantly, the design of electrochemical sensors using perovskite nanomaterials with low detection limit and high sensitivity will bring new insight into the detection of biomolecules. Both challenges and prospects of metal perovskites were discussed for promoting the development of biosensors in the end.

Engineering Local Graphitic Domains to Balance Defect Active Site and Electronic Conduction Ability in Coal‐Derived Carbon Anode for Superior Potassium Ions Storage

AbstractPotassium‐ion hybrid capacitors (PIHCs) are regarded as one of the promising candidates for large‐scale energy storage technologies. Nevertheless, the lack of suitable anode materials combined with fast ion diffusion kinetics and favorable cycle stability restricts their application. Herein, a catalyst‐confined graphitization strategy is proposed to synthesize low‐cost coal‐based carbon anodes, which have controllable heteroatom co‐doping and rich defect sites, together with local graphitic domains. Density functional theory calculations and kinetic analysis are performed to uncover the coupling effect for heteroatom dual‐doping and defective structures. Importantly, the introduction of graphitic domains ensures good electric conductivity and charge transfer kinetics while preserving rich defects and active sites. The optimized NC‐950 exhibits superior potassium storage capacity, which delivers a high reversible specific capacity (363.3 mAh g−1), impressive rate capability (93.9 mAh g−1 at 2 A g−1), and stable cycling performance. As a practical device application, the PIHCs (NC‐950//AC) are assembled using the NC‐950 anode and commercial activated carbon (AC) cathode, which exhibits the maximum energy density of 97.0 Wh kg−1 and excellent cycling stability (10 000 cycles). Significantly, this work unveils a new pathway to developing low‐cost and fast reaction kinetics carbon anode for advanced electrochemical supercapacitors.

Graphene Electrode for Studying CO2 Electroreduction Nanocatalysts under Realistic Conditions in Microcells.

The ability to resolve the dynamic evolution of electrocatalytically induced processes with electrochemical liquid-phase electron microscopy (EM)is limited by the microcell configuration. Herein, a free-standing tri-layer graphene is integrated as a membrane and electrode material into the electrochemical chip and its suitability as a substrate electrode at the high cathodic potentials required for CO2 electroreduction (CO2ER) is evaluated. The three-layer stacked graphene is transferred onto an in-house fabricated single-working electrode chip for use with bulk-like reference and counter electrodes to facilitate evaluation of its effectiveness. Electrochemical measurements show that the graphene working electrode exhibits a wider inert cathodic potential range than the conventional glassy carbon electrode while achieving good charge transfer properties for nanocatalytic redox reactions. Operando scanning electron microscopy studies clearly demonstrate the improvement in spatial resolution but reveal a synergistic effect of the electron beam and the applied potential that limits the stability time window of the graphene-based electrochemical chip. By optimizing the operating conditions, in situ monitoring of Cu nanocube degradation is achieved at the CO2ER potential of -1.1V versus RHE. Thus, this improved microcell configuration allows EM observation of catalytic processes at potentials relevant to real systems.

Printing surface cuprous oxides featured liquid metal for non-enzymatic electrochemical glucose sensor

Electrochemical glucose sensors that rely on two-dimensional (2D) oxides have attracted significant attention owing to the strong sensing activity of 2D oxides, but their practical application is hindered by the complexity and high cost of fabrication of electrodes and integrated devices. Herein, a convenient and effective fabrication route that includes printing a Ga-based liquid metal (LM) as a current collection electrode, followed by growing electrochemically active 2D oxides directly on the surface of Ga-based LMs under mild conditions, is developed for non-enzyme-based electrochemical sensors. Specifically, 2D annealed Cu-Oxide (ACO) is successfully grown on a printed Ga electrode through a galvanic replacement reaction, resulting in the formation of a mechanically and electrically well-matched interface between the active sensing materials and the current collection substrate. Benefitting from the high quantity of 2D ACO and good charge transfer at the interface, the as-prepared ACO electrode exhibits attractive glucose sensing performance, with a wide linear range (1 μM-10 mM) of effective detection, low detection limit down to 1 μM, and high sensitivity of 0.87 μA·mM-1·cm-2. Our study highlights the potential of using LMs in bio-sensing applications and provides a non-enzyme-based electrochemical biosensor platform for effective glucose detection in diets and clinical diagnostic settings.

Designing B–C3N4/Bi2WO6 to construct a Z-type hybrid heterostructure for efficient degradation of antibiotics

Constructing nanocomposite structures with good charge transfer pathways is an effective way to obtain high-efficiency photocatalysts. Therefore, we prepared a Z-scheme heterojunction B–C3N4/Bi2WO6 composite material by combining 2D B–C3N4 nanosheets and 2D Bi2WO6 nanosheets. The composite catalyst exhibited significant multi-purpose photocatalytic activity against the antibiotics. When the Bi2WO6 proportion was 100 % (The proportion of Bi2WO6 to B–C3N4 is 1:1), the degradation efficiency of TC-HCl reached 85.7 % within 90 min, demonstrating the best photocatalytic performance. UV–vis showed that the visible light response range of the photocatalytic material shifted to the infrared region, possibly due to the construction of a Z-type heterojunction. The PL results showed that the electron-hole recombination rate of B–C3N4 is lower than that of g-C3N4 due to B-doping. Doped heterostructures can effectively enhance the performance of photocatalytic materials and offer a novel approach to pollutant degradation.

Enhanced Hydroxyl Adsorption in Ultrathin NiO/Cr2 O3 In-Plane Heterostructures for Efficient Alkaline Methanol Oxidation Reaction.

The exploration of advanced nickel-based electrocatalysts for alkaline methanol oxidation reaction (MOR) holds immense promise for value-added organic products coupled with hydrogen production, but still remain challenging. Herein, we construct ultrathin NiO/Cr2 O3 in-plane heterostructures to promote the alkaline MOR process. Experimental and theoretical studies reveal that NiO/Cr2 O3 in-plane heterostructures enable a favorable upshift of the d-band center and enhanced adsorption of hydroxyl species, leading to accelerated generation of active NiO(OH)ads species. Furthermore, ultrathin in-plane heterostructures endow the catalyst with good charge transfer ability and adsorption behavior of methanol molecules onto catalytic sites, contributing to the improvement of alkaline MOR kinetics. As a result, ultrathin NiO/Cr2 O3 in-plane heterostructures exhibit a remarkable MOR activity with a high current density of 221 mA cm-2 at 0.6 V vs Ag/AgCl, which is 7.1-fold larger than that of pure NiO nanosheets and comparable with other highly active catalysts reported so far. This work provides an effectual strategy to optimize the activity of nickel-based catalysts and highlights the dominate efficacy of ultrathin in-plane heterostructures in alkaline MOR.

Nonplanar π-Conjugated Sulfur Heterocyclic Quinone Polymer Cathode for Air-Rechargeable Zinc/Organic Battery with Simultaneously Boosted Output Voltage, Rate Capability, and Cycling Life.

π-conjugated organic compounds with a good charge transfer ability and rich redox functional groups are promising cathode candidates for air-rechargeable aqueous Zn-based batteries (AAZBs). However, the output voltage of even the state-of-the-art π-conjugated organic cathodes lies well below 0.8 V, resulting in insufficient energy density. Herein, we design a nonplanar π-conjugated sulfur heterocyclic quinone polymer (SHQP) as an advanced cathode material for AAZBs by polymerization 1,4-Benzoquinone (BQ) and S heteroatoms periodically. The extended π-conjugated plane and enhanced aromaticity endow SHQP with a more sensitive charge transfer ability and robust structure. Furthermore, the delocalized π electrons in the whole system are insufficient as the π orbit of the S heteroatom is not in the same plane with the π orbit of BQ due to its folded configuration, resulting in negligible variation of electron density around C═O after the polymerization. Thus, the output voltage of SHQP shows no significant decrease even though the thioether bond (-S-) functions as electron donor. Consequently, the Zn/SHQP AAZBs can deliver a record high midpoint discharging voltage (0.95 V), rate performance (119 mAh g-1 at 10 A g-1), and durability (98.7% capacity retention after 200 cycles) across a wide temperature range.

Boosting adsorption and dissociation kinetics of magnesium-chloride ion pair via bismuth/indium-based artificial interface

The formation of passivating interphases on Mg-metal anode is impeding the wide employment of rechargeable Mg-metal batteries with less safety and cost concerns. Despite engineering artificial interlayers offers an efficient solution, it still falls short of expectation because of the compromised Mg plating/stripping performances in conventional electrolyte systems. In this work, a unique bismuth/indium-based artificial interface is introduced, which enables an exceptional reversibility (lowest nucleation overpotential of 189 mV than that (583 mV) of pristine Mg anode), high rate capability (a stable charge and discharge operation at 5.0 mA cm−2 without short circuit) and good temperaturetolerance (being cyclable over 10 °C and 50 °C) for the first time. This bismuth/indium-based artificial interface is constructed by facile displacement reactions between Bi(CF3SO3)3/In(CF3SO3)3 and Mg. The dominant interphases, including Bi, In and BiOx species, can be controllably tailored via adjusting the relative ratio and concentration of Bi(CF3SO3)3/In(CF3SO3)3. Theoretical calculation results accompanied by electrochemical experiments indicate that kinetically favorable adsorption and dissociation processes of Mg-Cl ion pair on this interface, affording good magnesiophilic property and fast charge transfer kinetics, are responsible for the improved Mg-metal anode properties.

ZnO/black phosphorus/C3N4 composite: An effective photocatalyst for Cr (VI) reduction and degradation of rhodamine B

The utilization of photocatalysts offers a promising approach for the removal of Cr (VI) and rhodamine dyes. Through the generation of reactive species and subsequent degradation reactions, photocatalysis provides an efficient and environmentally friendly method for the remediation of wastewater. In this study, we have synthesized an n-p-n heterojunction of carbon nitride (C3N4), zinc oxide (ZnO), and black phosphorus (BP) through the sonication-stirring method. The photocatalytic ability of this composite was examined for the decomposition rhodamine B (RhB) and detoxification of hexavalent chromium ion (up to 97% during 80 min) under Xenon irradiation. The results of trapper experiments indicated that the active species were hydroxyl radical (˙OH), electron (e−), and superoxide anion radical (˙O2−). Based on the obtained potential of the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbital (HOMO) for the mentioned semiconductors, through Mutt-Schottky results, the double Z-scheme mechanism was proposed for the studied process. The electrochemical impedance spectroscopy data exhibited good charge transfer for the evaluated composite versus the pure compounds. The impressive separation of holes and electrons along with the low recombination were confirmed by the responses of photocurrent and quenching the photoluminescence (pl) intensity for the composite, respectively. The current density of the composite recorded 66.6%, 87.3%, and 92% higher than those of BP, C3N4, and ZnO, indicating an excellent electron-hole separation for the ternary composite compared to the pure semiconductors. Diffuse reflectance spectra (DRS) data revealed 2.9, 3.17, 1.15, and 2.63 eV as the band gap values for C3N4, ZnO, BP, and composite. The rate constant of the new composite to remove RhB and reduce hexavalent chromium were about 4.79 and 2.64 times higher than that of C3N4, respectively.

Rational Design of a Copper Cobalt Sulfide/Tungsten Disulfide Heterostructure for Excellent Overall Water Splitting.

Integrating different components into a heterostructure is a novel approach that increases the number of active centers to enhance the catalytic activities of a catalyst. This study uses an efficient, facile hydrothermal strategy to synthesize a unique heterostructure of copper cobalt sulfide and tungsten disulfide (CuCo2S4-WS2) nanowires on a Ni foam (NF) substrate. The nanowire arrays (CuCo2S4-WS2/NF) with multiple integrated active sites exhibit small overpotentials of 202 (299) and 240 (320) mV for HER and OER at 20 (50) mA cm-2 and 1.54 V (10 mA cm-2) for an electrolyzer in 1.0 M KOH, surpassing commercial and previously reported catalysts. A solar electrolyzer composed of CuCo2S4-WS2 bifunctional electrodes also produced significant amounts of hydrogen through a water splitting process. The remarkable performance is accredited to the extended electroactive surface area, reasonable density of states near the Fermi level, optimal adsorption free energies, and good charge transfer ability, further validating the excellent dual function of CuCo2S4-WS2/NF in electrochemical water splitting.

Formulation of hydrophobic hybrid nano-ink with high interfacial potential for the electrochemical detection of triclosan

In the era of nanotechnology, there is a focus on making analytical devices smaller and more portable, enabling real-time, on-site detection. One approach to achieving this goal is to design a compact electrode using specialized nano ink. This work is focused on the nano-ink formulation. Its constituents include an active material (vinyl functionalized Polyhedral oligomeric silsesquioxane: V-POSS), infused with conductive carbon (multi-walled carbon nanotubes: MWCNT) additive (aids uniform electron conduction) along with the polymeric (Polyvinylidene fluoride: PVDF) binders dissolved in suitable solvents (Dimethyl formamide: DMF) to attain the thixotropic effect. The hydrophobic POSS-based hybrid material holding intriguing properties of tailorable functionality, high interfacial potential, and good charge transferability was embraced as the lead active material with the MWCNT conductive matrix. The physiochemical and electrochemical characterization of the formulated ink was carried out. Primary electrochemical sensing and optimization were performed using the conventional setup towards the detection of triclosan (TCL) (endocrine disruptor cum aquatic pollutant) detection. The real-time analysis to monitor the usage levels of TCL in perfumeries as quality control (QC) and in water samples was performed followed by cross-validation with the HPLC-UV technique. The developed V-POSS: MWCNT nano ink (POSS-based nano ink: PBNI) @GCE sensor showed a low detection limit of 0.43 pM with a sensitivity of 5.4316 µA/pM and a linear dynamic range of 1 pM – 1 nM indicating the excellent electrochemical activity of the formulation towards TCL monitoring.

Metal-Free Counter Electrodes for DSSCs Based on Nitrogen-Doped Reduced Graphene Oxide Materials

The importance of counter electrodes in Dye Sensitized Solar Cells (DSSCs) cannot be neglected as they enable the transfer of electrons across the outer circuit, thereby facilitating the reduction reaction of the I3−/I− redox electrolyte. However, the dissolution and deposition of the usual platinum layer on the counter electrode has resulted in contamination concerns. To address this issue, metal-free counter electrodes made of reduced graphene oxide (rGO) aerogels were developed and their catalytic performance towards I3− reduction was evaluated. The reduced graphene materials were characterized, and the fitting analysis of XPS revealed the presence of various nitrogen species, with the primary peaks attributed to pyridinic and pyrrolic nitrogen. The hydrothermal treatment of graphene oxide (GO) resulted in a higher graphitic character and the intensification of the contacts between graphene nanosheets, which should entail higher electrical conductivity, both in-plane and between rGO sheets. Additionally, the presence of nitrogen-provided active sites promoted the catalytic reduction of the electrolyte. Encouragingly, good charge transfer rates were observed between the counter electrode and the electrolyte in the assembled DSSCs, resulting in good photocurrents and exceptional stability over the course of nearly 1200 h after cell assembly. The results obtained suggest that these GO-based systems are promising candidates for developing metal-free counter electrodes for DSSC, supporting the interest of further study.

In situ exsolution of ternary alloy nanoparticles from perovskite oxides to realize enhanced oxygen evolution reactivity

Perovskite oxides are promising electrocatalysts for oxygen evolution reaction (OER), while the rational modification on their surface may further improve the performance. Herein, through facile in situ exsolution, CoFeNi ternary alloy nanoparticles exsolved on Sr0.9Co0.5Fe0.35Ni0.15O3-δ (SCFN) parent with embedded and well-anchored structure is proposed as an excellent electrocatalyst for OER. The strong metal-perovskite interaction caused by the exsolution generates the unique synergistic coupling effect, activating the surface oxygen to achieve oxygen species (O22-/O-) and inducing abundant oxygen vacancies and multiple active sites. The electrocatalyst SCFN350, which was reduced in 10 % H2/Ar at 350 ℃ for 1 h, exhibits remarkable OER performance with an overpotential of 282 mV at a current density of 10 mA cm-2 in 1.0 M KOH electrolyte and good durability for 10 h in practical operation. The low Tafel slope (36.53 mV dec−1) and small charge transfer resistance (8.50 Ω) indicate its good charge transfer kinetics and electrical conductivity during OER. Our work not only reveals that a nanostructured ternary alloy phase can be exsolved from the perovskite matrix but also confirms that in situ exsolution is an effective strategy for designing OER catalysts.