Modification of carbon paste electrode with Ni-clinoptilolite nanoparticles for electrocatalytic oxidation of methanol

Photothermal effect and hole transport properties of polyaniline for enhanced photoelectrochemical water splitting of BiVO4 photoanode

As modification strategies are actively developed, the photothermal effect is expected to be a viable way to enhance the PEC water splitting performance. Herein, we demonstrate that the photothermal polyaniline (PANI) layer inserted between CoF2 cocatalyst and BiVO4 can enhance the photocurrent density of pure BiVO4 by 3.50 times. The coated PANI layer exhibits excellent photothermal conversion and hole transport properties. Under near-infrared (NIR) light irradiation at 808 nm, PANI can raise the temperature of the photoanode in situ, thus promoting bulk charge transfer and broadening the light absorption range. After the CoF2 cocatalyst is deposited on the BiVO4/PANI surface, the water oxidation activity of the composite photoanode is also significantly enhanced due to the temperature elevation. In addition, density-functional theory (DFT) simulations demonstrate that BiVO4/PANI/CoF2 can dramatically reduce the energy barrier required for oxygen evolution reaction, accelerating the oxygen evolution kinetics. Under NIR light irradiation, the meticulously designed BiVO4/PANI/CoF2 (BPC) photoanode displays a photocurrent density of 4.34 mA cm-2 at 1.23 V vs. RHE (VRHE) with an excellent charge injection efficiency of 88.14 %. In addition, at 350 nm, the incident photon-to-current efficiency (IPCE) of the BPC photoanode reaches up to 60.45 %, which is much higher than that of pure BiVO4 (7.75 %). At 0.66 VRHE, the applied bias photon-to-current efficiency (ABPE) value of BPC photoanode can reach 1.37 %, which is 12.5 times higher than that of pure BiVO4. This simple and robust strategy provides a pathway to employ photothermal materials to design PEC water splitting photoanodes with excellent overall performance.

Nanoengineered lanthanum niobate nanocaviar anchored carbon nanofibers for trace level detection of menadione in environmental samples

An innovative sensor is prepared by electrode modification through a nano-ranged electrode modifier composed of LaNbO₄ nano caviars decorated on the enmeshed carbon nanofibers to identify excess vitamins in animal feed. Menadione (Vitamins K3) is a micronutrient fundamentally required in precise quantities for animal health upkeep. Still, its exploitation has recently resulted in water reservoir contamination through waste generated from animal husbandry. Sustainable prevention of water contamination makes menadione detection highly imperative and flickered the attention of researchers. Considering these aspects, a novel menadione sensing platform is designed by interdisciplinary incorporation of nanoscience and electrochemical engineering. The structural and crystallographic features and the electrode modifier's morphological insights were keenly investigated. The hierarchal arrangement of individual constituents in nanocomposite is benefited through hybrid heterojunction and quantum confinement that synchronously activate the menadione detection with a LOD of 68.5 nM and 67.49 nM for oxidation and reduction, respectively. The as-prepared sensor has a wide linear range (0.1-173.6 μM), high sensitivity, good selectivity, and stability. The application of this sensor is extended to a water sample to monitor the consistency of the proposed sensor.

Application of Metal-Organic Frameworks (MOFs) in Environmental Biosystems

Metal-organic frameworks (MOFs) are crystalline materials that are formed by self-assembling organic linkers and metal ions with large specific areas and pore volumes. Their chemical tunability, structural diversity, and tailor-ability make them adaptive to decorate many substrate materials, such as biomass-derived carbon materials, and competitive in many environmental biosystems, such as biofuel cells, bioelectrocatalysts, microbial metal reduction, and fermentation systems. In this review, we surmised the recent progress of MOFs and MOF-derived materials and their applications in environmental biosystems. The behavior of MOFs and MOF-derived materials in different environmental biosystems and their influences on performance are described. The inherent mechanisms will guide the rational design of MOF-related materials and lead to a better understanding of their interaction with biocomponents.

Recent advances in the electrochemical applications of Ni-based metal organic frameworks (Ni-MOFs) and their derivatives

Nickel-based metal-organic skeletal materials (Ni-MOFs) are a new class of inorganic materials that have aroused attention of investigators during past couple of years. They offer advantages such as high specific surface area, structural diversity, tunable framework etc. This assorted class of materials exhibited catalytic activity and electrochemical properties and display wide range of applications in the fields of electrochemical sensing, electrical energy storage and electrocatalysis. In this context, the presented review focuses on strategies to improve the electrochemical performance and stability of Ni-MOFs through the optimization of synthesis conditions, the construction of composite materials, and the preparation of derivatives of precursors. The review also presents the applications of Ni-MOFs and their derivatives as electrochemical sensors, energy storage devices, and electrocatalysts. In addition, the challenges and further electrochemical development prospects of Ni-MOFs have been discussed.

Cathode materials for aqueous zinc-ion batteries: A mini review

Although lithium-ion batteries (LIBs) have many advantages, they cannot satisfy the demands of numerous large energy storage industries owing to their high cost, low security, and low resource richness. Aqueous zinc-ion batteries (ZIBs) with low cost, high safety, and high synergistic efficiency have attracted an increasing amount of attention and are considered a promising choice to replace LIBs. However, the existing cathode materials for ZIBs have many shortcomings, such as poor electron and zinc ion conductivity and complex energy storage mechanisms. Thus, it is crucial to identify a cathode material with a stable structure, substantial limit, and suitability for ZIBs. In this review, several typical cathode materials for ZIBs employed in recent years and their detailed energy storage mechanisms are summarized, and various methods to enhance the electrochemical properties of ZIBs are briefly introduced. Finally, the existing problems and expected development directions of ZIBs are discussed.

One-dimensional nitrogen-doped carbon frameworks embedded with zinc-cobalt nanoparticles for efficient overall water splitting

Metal-organic frameworks (MOFs)-derived catalysts exhibit highly-efficient hydrogen or oxygen evolution performance on water splitting. However, it is an urgent problem to construct bifunctional electrocatalysts for both hydrogen and oxygen evolution performance. Herein, we adopted Ag nanowires as templates to prepare one-dimensional Ag nanowire@ZIF-8@ZIF-67 precursors (1D AgNW@ZIF-8@ZIF-67). Through pyrolysis, AgNW@ZIF-8@ZIF-67 precursors transformed into nitrogen-doped carbon frameworks (NCF) embedded with zinc-cobalt (ZnCo) nanoparticles on the surface of Ag NWs (denoted as Ag@ZnCo/NCF nanohybrids). The nanohybrids were consisted of Ag NWs with good conductivity and ZnCo/NCF nanohybrids with rich accessible active sites. Benefiting from their large specific surface area, accessible active sites and synergistic effect among components, Ag@ZnCo/NCF nanohybrids exhibit lower overpotentials of 139 mV and 279 mV at the current density of 10 mA cm^-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution, severally. Compared with other catalysts, Ag@ZnCo/NCF nanohybrids possess smaller Tafel slope, indicating their higher catalytic activity. This work provides a new perspective for designing low-cost and highly efficient bifunctional electrocatalysts for overall water splitting.

Electrocatalytic Properties of 3D Hierarchical Graphitic Carbon-Cobalt Nanoparticles for Urea Oxidation

A 3D hierarchical graphitic carbon nanostructure encapsulating cobalt(0)/cobalt oxide nanoparticles (CoGC) has been prepared by solid-state pyrolysis of a mixture of anthracene and cobalt 2,2'-bipyridine terephthalate complex at 850 °C. Based on the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, the prepared material has high surface area (186.8 m² g^-1) with an average pore width of 205.5 Å. XPS reveals the functionalization of carbon with different oxygen-containing groups, such as carboxylic acid groups. The presence of metallic cobalt nanoparticles with cubic and hexagonal crystalline structures encapsulated in graphitized carbon is confirmed using XRD and TEM. Raman spectroscopy indicates a graphitization degree of I _D/I _G = 1.02. CoGC was cast onto a glassy carbon electrode and used for urea electrooxidation in an alkaline solution. The electrochemical investigation shows that the newly prepared CoGC has a promising electrocatalytic activity toward urea. The specific activity is 128 mA cm^-1 mg^-1 for the electrooxidation of 0.3 M urea in 1 M KOH at a relatively low onset potential (0.31 V vs Ag/AgCl). It can be mainly attributed to the morphological structure of carbon and the high reactivity of cobalt nanoparticles. The calculated charge-transfer resistance, R _ct, of the modified electrode in the presence of urea (10.95 Ω) is significantly lower than that in the absence of urea (113.5 Ω), which indicates electrocatalytic activity. The value of charge-transfer rate constant, k _s, for the anodic reaction is 0.0058 s^-1. Electrocatalytic durability in 1000 s chronoamperometry of the modified electrode suggests high structure stability. The modified electrode retained about 60% of its activity after 100 cycles as indicated by linear sweep voltammetry.

Efficient recovery of Cu(II) by LTA-zeolites with hierarchical pores and their resource utilization in electrochemical denitrification: Environmentally friendly design and reutilization of waste in water

Water pollution seriously endangers human health and the environment. Here we prepared and tested mesoporous LTA zeolites for the adsorption of Cu(II) from aqueous media and the captured copper was further used for electrochemical nitrate reduction. The prepared hierarchically porous LTA exhibited a high capacity (341.5 mg g^-1) for Cu(II) adsorption, following the pseudo-second-order kinetic and Freundlich adsorption isotherm models well. The Cu-LTA sample was characterised by various analytical methods, and Cu(I) species were identified as the active sites for nitrate electrochemical reduction. Based on the spectral characterization and reducibility, strong metal-support interaction was found between copper and LTA, which is beneficial to the dispersion of active sites and their contacts with nitrates. In total, 10.1 g-N-NO₃ g^-1-Cu was reduced over the Cu-LTA-modified cathode in a three-electrode system with high N₂ selectivity (92.1 %). Compared to purely microporous zeolites, mesoporous LTA has a higher capacity for Cu(II) removal and nitrate reduction. The mesoporous structure allows easy access to the inner active sites with low diffusion resistance. The low Tafel slope and high current density confirm the high activity of the mesoporous Cu-LTA, making it a promising and efficient material for the removal and reuse of heavy metal ions.

Recent Advances in Functionalized Mesoporous Silica Frameworks for Efficient Desulfurization of Fuels

Considerable health and climate benefits arising from the use of low-sulfur fuels has propelled the research on desulfurization of fossil fuels. Ideal fuels are urgently needed and are expected to be ultra-low in sulfur (10-15 ppm), with no greater than 50 ppm sulfur content. Although several sulfur removal techniques are available in refineries and petrochemical units, their high operational costs, complex operational needs, low efficiencies, and higher environmental risks render them unviable and challenging to implement. In recent years, mesoporous silica-based materials have emerged as promising desulfurizing agents, owing to their high porosity, high surface area, and easier functionalization compared to conventional materials. In this review, we report on recent progress in the synthesis and chemistry of new functionalized mesoporous silica materials aiming to lower the sulfur content of fuels. Additionally, we discuss the role of special active sites in these sorbent materials and investigate the formulations capable of encapsulating and trapping the sulfur-based molecules, which are challenging to remove due to their complexity, for example the species present in JP-8 jet fuels.

Lattice substitution and desulfurization kinetic analysis of Zn-based spinel sorbents loading onto porous silicoaluminophosphate zeolites

Green Zn-based spinel sorbents for hot coal gas desulfurization have been developed with the assistance of optimization procedures. The pilot study highlights an outstanding ordered mesoporous support (S_BET = 323 m² g^-1, Da = 4.3 nm) of SAPO-34@as-prepared SBA-15 (SS) for loading active metal oxides. ZnCo₂O₄ spinel loaded onto SS (ZnCo₂/SS) exhibits a prominent desulfurization performance compared to other sorbents whose partial Co is substituted by Mn or Fe in spinel B-site, owing to the slight effect of PO₄^3- in SS. After systematic evaluation on role of sulfidation condition, 50 wt% ZnCo₂/SS sorbent possesses the sulfur storage capacity of 138.08  mg g^-1at550 °C and little loss of active species in 5 desulfurization-regeneration cycles. Results of high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) etc. demonstrate that 70.42% of initial sulfur capacity of ZnCo₂/SS presented in the 2nd utilization is associated with zinc evaporation, existence of high stable sulfides and partial sintering. The improved deactivation kinetic model suitably describes that the H₂S concentration distribution relates with the spatial position of fixed-bed reactor and desulfurization time.

Photocatalytic performance of TiO2/Clinoptilolite: Comparison study in suspension and hybrid photocatalytic membrane reactor

Comparison studies in suspension and hybrid photocatalytic membrane reactor (HPMR) system was investigated by using Reactive Black 5 (RB5) as target pollutant under UVA light irradiation. To achieve this aim, hybrid TiO₂/clinoptilolite (TCP) photocatalyst powder was prepared by solid-state dispersion (SSD) methods and embedded at the outer layer of dual layer hollow fiber (DLHF) membranes fabricated via single step co-spinning process. TiO₂ and CP photocatalyst were also used as control samples. The samples were characterized by Scanning Electron Microscopy (SEM), Energy Dispersion of X-ray (EDX), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses. The result shows that TCP was actively functioned as photocatalyst in suspension system and 86% of RB5 photocatalytic degradation achieved within 60 min; however the additional step is required to separate the catalyst with treated water. In the HPMR system, even though the RB5 photocatalytic degradation exhibits lower efficiency however the rejection of RB5 was achieved up to 95% under UV irradiation due to the properties of photocatalytic membranes. The well dispersed of TCP at the outer layer of DLHF membrane have improved the surface affinity of DL-TCP membrane towards water, exhibit the highest pure water flux of 41.72 L/m².h compared to DL-TiO₂ membrane. In general, CP can help on improving photocatalytic activity of TiO₂ in suspension, increased the RB5 removal and the permeability of DLHF membrane in HPMR system as well.

Study of the interactions of influencing parameters on electrocatalytic determination of dopamine by a carbon paste electrode based on Fe(ii)–clinoptilolite nanoparticles

In this study, after ion exchange of clinoptilolite nanoparticles (CLN) in Fe(ii) solution, the prepared Fe(ii)–CLN was used for the modification of a carbon paste electrode (CPE).

A novel cysteine sensor based on modification of carbon paste electrode by Fe(II)-exchanged zeolite X nanoparticles

An electrochemical sensor based on carbon paste electrode (CPE) modified with iron(II) doped into a synthesized nano-particles of zeolite X (Fe(II)-NX/ZCME) was constructed, which is highly sensitive for detection of cysteine (Cys). The modified electrode showed an excellent electro-activity for oxidation of Cys in phosphate buffer at pH7.4. It has been found that anodic peak potential of Cys oxidation, compared with the unmodified CPE (UCPE), was shifted towards negative values at the surface of the modified electrode under the optimum condition. The peak current increased linearly with the Cys concentration in the wide range of 5.0 × 10(-9)-3.0 × 10(-3) mol L(-1). The very low detection limit was obtained to be 1.5 × 10(-10) mol L(-1). Finally, the modified electrode was used as a selective, simple and precise new electrochemical sensor for the determination of Cys in the real samples, such as pharmaceutical and biological fluids.