Hybrid ternary NiCoCu layered double hydroxide electrocatalyst for alkaline hydrogen and oxygen evolution reaction.

This study focuses on the electrochemical properties of layered double hydroxide (LDH), which is a specific structure of NiCoCu LDH, and the active species therein, rather than the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of ternary NiCoCu LDH materials. Six types of catalysts were synthesized using the reflux condenser method and coated onto a nickel foam support electrode. Compared to bare, binary, and ternary electrocatalysts, the NiCoCu LDH electrocatalyst exhibited higher stability. The double layer capacitance (Cdl) of the NiCoCu LDH (12.3 mF cm-2) is greater than that of the bare and binary electrocatalysts, indicating that the NiCoCu LDH electrocatalyst has a larger electrochemical active surface area. In addition, the NiCoCu LDH electrocatalyst has a lower overpotential of 87 mV and 224 mV for the HER and OER, respectively, indicating its excellent activity with the bare and binary electrocatalysts. Finally, it is demonstrated that the structural characteristics of the NiCoCu LDH contribute to its excellent stability in long-term HER and OER tests.

Graphene-based strontium niobate-zinc oxide heterojunction photocatalyst for effective reduction of hexavalent chromium.

A hydrothermal technique was employed to synthesize a Sr2Nb2O7-rGO-ZnO (SNRZ) ternary nanocatalyst, in which ZnO and Sr2Nb2O7 were deposited on reduced graphene oxide (rGO) sheets. The surface morphologies, optical properties, and chemical states, of the photocatalysts were characterized to understand their properties. The SNRZ ternary photocatalyst was superior over the reduction of Cr (VI) to harmless Cr (III) compared to the efficiencies obtained using bare, binary, and composite catalysts. The effects of various parameters, including the solution pH and weight ratio, on the photocatalytic reduction of Cr (VI) were investigated. The highest photocatalytic reduction performance (97.6%) was achieved at pH 4 and a reaction time of 70 min. Photoluminescence emission measurements were used to confirm efficient charge migration and separation across the SNRZ, which improved the reduction of Cr (VI). A feasible reduction mechanism for the SNRZ photocatalyst is proposed. This study presents an effective, inexpensive, non-toxic, and stable catalyst, for the reduction of Cr (VI) to Cr (III) using SNRZ ternary nanocatalysts.

Locust Bean gum-based hydrogels embedded magnetic iron oxide nanoparticles nanocomposite: Advanced materials for environmental and energy applications.

This paper reports a simple method of designing and synthesizing magnetic iron oxide (IO) integrated locust bean gum-cl-polyacrylonitrile hydrogel nanocomposites (LBG-cl-PAN/IONP) by in situ mineralization of iron ions in a hydrogel matrix. A two-step gel crosslink method followed by co-precipitation method was used to prepare these novel hydrogels embedded with magnetic iron oxide nanoparticles. The LBG-cl-PAN/IONP hydrogel nanocomposite (HNC) were tested in batch adsorption experiments for their ability to remove a cationic dyes, methylene blue (MB) & Methyl violet (MV), from aqueous solution. In order to analyze the LBG-cl-PAN/IONP HNC, FTIR, XRD, XPS, VSM, TEM, and EDX techniques were applied. Numerous operating parameters were studied, including the amount of adsorbent, the contact time, pH, temperature, the dye concentration, and the coexisting ion concentration. According to the Langmuir isotherm model, MB and MV had maximum monolayer adsorptive capacities of 1250 and 1111 mg/g, respectively. LBG-cl-PAN/IONP HNC controlled IONP oxidation as well as sustained adsorptive removal over a wide pH range (7-10). The key mechanism of adsorption consisted of electrostatic interaction and ion exchange. For successful use in successive cycles after regeneration using HNO3 as eluent, the LBG-cl-PAN/IONP HNC can easily be reused. As a material, the LBG-cl-PAN/IONP HNC is a promising sorbent or composite material for removing toxic dyes from water, and therefore can be applied to enhance water and wastewater treatment technology. Additionally, we have briefly evaluated LBG-cl-PAN/IONP HNC for antibacterial and supercapacitor applications. According to our knowledge, this is the first report describing the use of LBG-cl-PAN/IONP HNC multifunctional efficacy as an excellent sorbent, antibacterial and electrochemical supercapacitor applications.

Band structure alignment transitioning strategy for the fabrication of efficient photocatalysts for solar fuel generation and environmental remediation applications.

Indium hydroxide (In(OH)3) and indium oxide (In2O3) have proven to be efficient catalysts for photocatalytic water-splitting reactions to produce hydrogen (H2) and for organic pollutant degradation applications. However, the limited optical absorption features of indium-based nanostructures have restricted their practical applications. In this study, we have successfully designed indium hydroxide- and indium oxide-loaded metal sulfide (cadmium sulfide, CdS) heterostructures as excellent photocatalytic systems for photocatalytic hydrogen evolution and tetracycline hydrochloride pollutant degradation reactions. In this system, In(OH)3 and In2O3 established Type-I and S-scheme heterojunctions, respectively, with CdS, resulting in superior charge separation properties and outstanding photocatalytic activity. Specifically, the rational and appropriate design of the aforementioned indium-based heterostructures promoted the separation of photoexcited charge carriers via Type-I and S-scheme paths. Accordingly, enhanced photocatalytic H2 evolution activities of 9.58 and 14.98 mmol·g-1·h-1 were achieved for CdS-In(OH)3 and CdS-In2O3, respectively. Furthermore, the highest degradation efficiency of CdS-In2O3 was âˆ¼ 90%, which was higher than those of CdS-In(OH)3 (72%) and bare CdS nanorods (51%). Therefore, the results of this study provide an opportunity to enhance the catalytic activities of heterostructured photocatalytic systems by utilizing the strategy of transitioning band structure alignment from the Type-I to the S-scheme.

Synergistic sorption performance of karaya gum crosslink poly(acrylamide-co-acrylonitrile) @ metal nanoparticle for organic pollutants.

In this work, we tailor facile hydrogels nanocomposite (HNC) based on sustainable karaya gum for water treatment. Karaya gum crosslink poly(acrylamide-co-acrylonitrile) @ silver nanoparticle (KG-cl-P(AAm-co-AN)@AgNPs) HNC were made by an aqueous free radical in situ crosslink copolymerization of acrylamide (AAm) and acrylic acid (AA) in aqueous solution of KG-stabilized AgNPs. FTIR, XRD, DTA-TGA, SEM, and TEM were used to characterize HNC. The hydrogels' swelling, diffusion, and network characteristics were investigated. The removal efficiency of HNC was found to be 99% at pH 8 for a crystal violet (CV), dose of 0.02 g after 1 h. Dye adsorption by these hydrogels was also investigated in terms of isotherms, and kinetics. The dye's exceptionally high adsorption capacity on HNC for CV removal is explained by H-bonding interactions, as well as dipole-dipole and electrostatic interactions between anionic adsorbent and cationic dye molecules (Qmax, 1000 mg/g). The HNC can be regenerated with 0.1 M HCl and reused at least 10 times maintaining over 68% dye removal. The loading of AgNPs into the polymeric matrix of KG-cl-P(AAm-co-AN) significantly increases the removal percentage of CV dye from its aqueous solution, according to this study.

Bismuth quantum dots anchored one-dimensional CdS as plasmonic photocatalyst for pharmaceutical tetracycline hydrochloride pollutant degradation.

Earth abundant metal based plasmonic photocatalysis is one of the most proficient approaches to degrade the emergent organic pollutants in contaminated water. Here, we report that using one-dimensional CdS/zero-dimensional Bi quantum dot (QD) heterostructures (1D/0D CdS/Bi HSs) were obtained via a simple solvothermal reaction. The results specified that the Bi QDs were grown onto CdS NRs through the reduction of Bi3+ ions. The Bi modified CdS HSs were employed as a photocatalyst for pharmaceutical pollutant tetracycline degradation and the optimized sample showed the maximum photocatalytic degradation activity of 90% under visible light radiation within 60 min, which is greater than the pure CdS (52%) under identical conditions. Based on the structural characterizations and degradation efficiency, the obtained CdS/Bi is a promising photocatalyst for the treatment of wastewater which contains emerging pollutants such as organic dyes and pharmaceutical antibiotics during the industrial processes. The boosted photocatalytic degradation efficiency is credited to the doped Bi3+ species; surface plasmon resonance effect that raised from metallic Bi QDs and proficient photoinduced charge carriers separation.

CuS/Ag2O nanoparticles on ultrathin g-C3N4 nanosheets to achieve high performance solar hydrogen evolution.

Ternary heterostructures play a crucial role in improving the separation of charge carriers and fast surface reaction kinetics, which in turn helps in understanding the effective photocatalytic water splitting performance. Herein, CuS/Ag2O nanoparticles were presented on a graphitic carbon nitride (g-C3N4) surface to obtain CuS/Ag2O/g-C3N4 material using facile hydrothermal and precipitation methods. Structural and morphological studies confirmed the presence of ternary nanostructures comprising CuS, Ag2O, and g-C3N4 with nanoparticle and nanosheet morphologies. The as-synthesized CuS/Ag2O/g-C3N4 exhibited a remarkable photocatalytic H2 production of 1752 µmol.h-1.g-1cat, which is considerably superior than those of CuS and g-C3N4. The improved H2 production performance which is due to the effective interfacial CuS/Ag2O/g-C3N4 heterojunction interface and superior hole (h+) trapping capability of the CuS at the CuS/Ag2O/g-C3N4 interface. This can efficiently enhance the lifetime of photoexcited charge carriers and enhance the electron density for the production of H2. The optimum CuS/Ag2O/g-C3N4 heterostructure remained stable after 8 successive experimental cycles, although with a slight change in the H2 production rate. Therefore, this study offers a novel approach to exploit the efficacy through the synergetic effect of integrating CuS as the photocatalyst and Ag2O as the visible sensitizer, thus proposing a viable strategy of using earth-abundant material to enhance the conversion of solar energy to fuel.

Synergistic effects of Tin sulfide Nitrogen-doped titania Nanobelt-Modified graphitic carbon nitride nanosheets with outstanding photocatalytic activity.

Designing efficient ternary nanostructures is a feasible approach for energy production under simulated solar irradiation. In this study, excellent photoexcited charge carrier separation and enhanced visible-light response were achieved with nitrogen-doped titania nanobelts (N-TNBs), whose 1D geometry facilitated the fabrication of a heterostructure with SnS2 on the surface of graphitic carbon nitride (g-C3N4). We established the design of SnS2@N-TNB and SnS2@N-TNB/g-C3N4 heterostructures by in situ hydrothermal and ultrasonication processes, and achieved commendable simulated solar light driven photocatalytic H2 generation. UV-vis diffuse reflectance spectroscopy analysis revealed a red shift in the absorption spectra of the SnS2@N-TNB and SnS2@N-TNB/g-C3N4 samples. The H2 produced via SnS2@N-TNB-10/g-C3N4 (6730.8 µmol/g/h) was 2.6 times higher than that produced by SnS2@N-TNB (2515.1 µmol/g/h), and 299 times higher than that produced by N-TNB (22.5 µmol/g/h). The improved photocatalytic H2 production was attributed to the maximum interface contact between SnS2@N-TNB and g-C3N4, and to the improved visible-light absorption and effective charge-carrier separation. Therefore, the present study provides novel insights for combining the advantages of ternary materials to improve the conversion of solar energy to H2 fuel.

Facile synthesis of sphere-like structured ZnIn2S4-rGO-CuInS2 ternary heterojunction catalyst for efficient visible-active photocatalytic hydrogen evolution.

Photocatalysis is a promising approach for generating hydrogen, an eco-friendly and cost-effective fuel. It is hypothesized that the ternary catalyst ZnIn2S4-rGO-CuInS2, prepared by ultrasonication method, should be effective for optimized photocatalytic hydrogen generation in a Na2S/Na2SO3-water mixture. The as-synthesized catalyst was characterized using various surface analytical and optical techniques. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy analyses revealed that marigold-like structured ZnIn2S4 and layer-structured CuInS2 were dispersed on the reduced graphene oxide sheets. The ternary ZnIn2S4-rGO-CuInS2 system showed enhanced photocatalytic H2 production compared to pure ZnIn2S4, CuInS2, ZnIn2S4-rGO, CuInS2-rGO, and ZnIn2S4-CuInS2 catalysts under visible light illumination. The fabricated ZnIn2S4-rGO-CuInS2 catalyst afforded hydrogen generation of 2531 µmol/g after 5 h. The enhanced performance of the ZnIn2S4-rGO-CuInS2 catalyst originates from the synergetic effect with rGO as the electron transfer medium, and is confirmed by photocurrent density and photoluminescence measurements that indicate reduced recombination between the excited electron and hole pairs, and fast electron transfer in the ternary composite. The excellent performance of the ZnIn2S4-rGO-CuInS2 catalyst for up to three consecutive cycles was demonstrated in cyclic stability tests under visible-light illumination.

Construction of visible-light driven Bi2MoO6-rGO-TiO2 photocatalyst for effective ofloxacin degradation.

Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi2MoO6-rGO-TiO2 composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h+) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi2MoO6-rGO-TiO2 was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.

Improved charge carrier separation of Schottky junction containing a bimetallic Cu-Pd alloy and N-Bi2WO6 square-shaped discs for photocatalytic H2 performance.

Bimetallic alloy nanospheres hybridized with semiconductor square-shaped discs are promising catalysts for photocatalytic water splitting, because they exhibit multicomponent interactions, high catalytic activity, and stability. Herein, Cu-Pd/N-Bi2WO6 heterostructures consisting of bimetallic Cu-Pd alloy nanospheres uniformly dispersed on N-Bi2WO6 square-shaped discs are reported. The as-prepared 1 wt% Cu-Pd/N-Bi2WO6 catalyst exhibits a higher H2 production rate (4213 µmol/g) under simulated solar light illumination than N-Bi2WO6 (291 µmol/g). The considerably high H2 production rate is ascribed to the exposed catalytically active sites of the Cu-Pd alloy nanospheres, which facilitate the formation of rapid charge transfer channels between Cu-Pd and N-Bi2WO6. Moreover, the photocatalyst stability is improved by aggregation of the highly dispersed Cu-Pd alloy nanospheres on the N-Bi2WO6 surface. Accordingly, a reaction mechanism based on the work functions of the bimetallic Cu-Pd alloy nanospheres and N-Bi2WO6 square-shaped discs is proposed to elucidate the photocatalytic reaction pathway. The holes (which accumulate in the N-Bi2WO6 square-shaped discs) and Pd (which acts as an electron channel) can effectively inhibit the recombination of charge carriers, and Cu (which acts as the cocatalyst) can synergistically increase the H+ reduction rate. This study provides a new effective route for the design of high-performance heterostructures for efficient photocatalytic H2 production.

Plasmonic quaternary heteronanostructures (HNSs) for improved solar light utilization, spatial charge separation, and stability in photocatalytic hydrogen production.

Recently, the frenetic development of stable quaternary material with a wide range of solar energy absorption and separation of charge carrier has emerged as a favorable material for the solar-to-hydrogen conversion. In this work, quaternary CuS-AgVO3/Ag-TNR heteronanostructures (HNSs) synthesized by an ultra-sonication method for stabilized solar light photocatalytic hydrogen production in glycerol-water mixture. Among the prepared photocatalysts, the 1 wt% CuS-AgVO3/Ag-TNR HNS produced the highest H2 activity (756 µmol/g), approximately 84 times greater than the TNR due to higher charge separation, excellent conductivity, plasmonic resonance effect, and electron-storing capacity. Interestingly, the accelerated charge transfer pathway through the Schottky junction between the AgVO3 and Ag to the conduction band of the TNR and thereafter to the electron acceptor of CuS for the reduction of H+ ions to H2. Additionally, a possible photocatalytic mechanism of CuS-AgVO3/Ag-TNR HNS for improved H2 production was proposed based on the results obtained by various characterization techniques. Therefore, present research work explores the new insights to design high-performance CuS-AgVO3/Ag-TNR HNS material for the conversion of clean renewable H2 energy for the futuristic transport applications.

Enhanced Electrochemical Properties and OER Performances by Cu Substitution in NiCo2O4 Spinel Structure.

In order to improve the electrochemical performance of the NiCo2O4 material, Ni ions were partially substituted with Cu2+ ions having excellent reducing ability. All of the electrodes were fabricated by growing the Ni1-xCuxCo2O4 electrode spinel-structural active materials onto the graphite felt (GF). Five types of electrodes, NiCo2O4/GF, Ni0.875Cu0.125Co2O4/GF, Ni0.75Cu0.25Co2O4/GF, Ni0.625Cu0.375Co2O4/GF, and Ni0.5Cu0.5Co2O4/GF, were prepared for application to the oxygen evolution reaction (OER). As Cu2+ ions were substituted, the electrochemical performances of the NiCo2O4-based structures were improved, and eventually the OER activities were also greatly increased. In particular, the Ni0.75Cu0.25Co2O4/GF electrode exhibited the best OER activity in a 1.0 M KOH alkaline electrolyte: the cell voltage required to reach a current density of 10 mA cm-2 was only 1.74 V (η = 509 mV), and a low Tafel slope of 119 mV dec-1 was obtained. X-ray photoelectron spectroscopy (XPS) analysis of Ni1-xCuxCo2O4/GF before and after OER revealed that oxygen vacancies are formed around active metals by the insertion of Cu ions, which act as OH-adsorption sites, resulting in high OER activity. Additionally, the stability of the Ni0.75Cu0.25Co2O4/GF electrode was demonstrated through 1000th repeated OER acceleration stability tests with a high faradaic efficiency of 94.3%.

Controlled Growth and Bandstructure Properties of One Dimensional Cadmium Sulfide Nanorods for Visible Photocatalytic Hydrogen Evolution Reaction.

One dimensional (1D) metal sulfide nanostructures are one of the most promising materials for photocatalytic water splitting reactions to produce hydrogen (H2). However, tuning the nanostructural, optical, electrical and chemical properties of metal sulfides is a challenging task for the fabrication of highly efficient photocatalysts. Herein, 1D CdS nanorods (NRs) were synthesized by a facile and low-cost solvothermal method, in which reaction time played a significant role for increasing the length of CdS NRs from 100 nm to several micrometers. It is confirmed that as the length of CdS NR increases, the visible photocatalytic H2 evolution activity also increases and the CdS NR sample obtained at 18 hr. reaction time exhibited the highest H2 evolution activity of 206.07 µmol.g-1.h-1. The higher H2 evolution activity is explained by the improved optical absorption properties, enhanced electronic bandstructure and decreased electron-hole recombination rate.

Oxygen Transfer Capacity of Pseudobrookite Particles Derived from Ilmenite Mineral (x wt.%CuO/y wt.%red Mud-z wt.%ilmenite).

The minerals have a somewhat slower than other transition metals at critical reduction rates in their ability to deliver oxygen. Thus, single minerals alone do not exhibit a higher oxygen transfer capacity than metal oxide oxygen carriers. In this study, we try to solve the problem of single mineral ilmenite (FeTiO3) by combining it with Fe-based red mud and Cu oxide. When the ilmenite was used without calcination, the CH4-CO/air redox cycle showed rapid decayed. However, when ilmenite was calcined, the CH4-CO/air redox cycle became stable, and the oxygen transfer rate increased to 4.2%. This is because the FeTiO3 structure was converted to the pseudobrookite (Fe2TiO5) structure through the calcination process. That is, the Fe2+ ion in the ilmenite structure was converted into an Fe3+ ion. When 30 wt.% of red mud was added to the Fe ion, it reacted with the rutile-type titania mixed with pseudobrookite-typed Fe2TiO5, producing an almost perfect pseudobrookite crystal. This resulted in a slight increase in the capacity of oxygen transfer to 4.9%. When 15 wt.% of Cu oxide was added, the oxygen transfer capacity increased to 6.0%. This performance was indicated by the cyclic voltammetry curve that remained constant even after 200 cycles. Here, we argue that if low-cost minerals as a base material are used in appropriate amounts, the production of a lowest-cost oxygen carrier can be achieved.