Search

Transition metal oxides (TMO) are promising candidates for low‐cost and high‐efficiency catalysts for the hydrogen evolution reaction (HER). However, the low conductivity and severe agglomeration of catalyst particles hinder their practical application. Herein, we report an effective HER electrocatalyst of 3D‐rGO‐CeO2 with three‐dimensional reduced graphene oxide (3D‐rGO) decorated with CeO2 hollow microspheres through a hydrothermal self‐assembly approach. It is shown that the CeO2 hollow microspheres with an average size of ca. 680 nm are uniformly encapsulated within the porous structure of 3D‐rGO. Compared with bare CeO2 hollow microspheres, the 3D‐rGO‐CeO2 composite exhibits remarkably enhanced electrocatalytic activity for HER with a relatively low onset overpotential of 192 mV, a smaller overpotential of 0.34 V at the current density of 10 mA cm–2, and a modest Tafel slope of 112.8 mV decade–1 in a 1 m KOH solution. The enhanced performance of 3D‐rGO‐CeO2 can be ascribed to the introduction of 3D rGO in the composite, which provides a highly conductive network for rapid charge‐carrier transmission, and rich porous structures for the easy access of the electrolyte to the catalyst during the HER process. [ABSTRACT FROM AUTHOR]

An efficient N-doped reduced graphene oxide (N-RGO)/Ag3PO4 nanocomposite with enhanced photocatalytic activity has been prepared through a facile solution-based approach. Since N-RGO could offer more sites for the anchoring of Ag3PO4 nanoparticles, and effectively promote the charge carriers separation and transfer due to its high electrical conductivity, the photocatalytic activity of N-RGO/Ag3PO4 nanocomposite is much higher than bare Ag3PO4 and N-RGO in the degradation of phenol pollutant under simulated solar light irradiation. The mechanism for the photocatalytic process was also investigated. The excellent photocatalytic performance makes the N-RGO/Ag3PO4 nanocomposite a promising photocatalyst for organic pollutant treatment. A N-doped reduced graphene oxide (N-RGO)/Ag3PO4 nanocomposite is prepared through a facile solutionbased approach. The nanocomposite exhibits enhanced photocatalytic activity for phenol degradation. The mechanism of the photocatalytic reaction is proposed. [ABSTRACT FROM AUTHOR]

Abstract: A simple one-step method to fabricate hierarchically porous TiO2/Pd composite hollow spheres without any template was developed by using solvothermal treatment. Pd nanoparticles (2–5nm) were well dispersed in the mesopores of the TiO2 hollow spheres via in-situ reduction. In our experiment, polyvinylpyrrolidone played an important role in the synthetic process as the reducing agent and the connective material between TiO2 and Pd nanoparticles. HF species generated from solvothermal reaction leaded to the formation of TiO2 hollow spheres and Ostwald ripening was another main factor that affected the size and structure of the hollow spheres. The as-prepared TiO2/Pd composite hollow spheres exhibited high electrocatalytic activity towards the reduction of H2O2. The sensitivity was about 226.72μAmM−1 cm−2 with a detection limit of 3.81μM at a signal-to-noise ratio of 3. These results made the hierarchically porous TiO2/Pd composite a promising platform for fabricating new nonenzymic biosensors. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline (PANI)/Fe3O4 composite hollow spheres have been successfully synthesized in one step using sulfonated polystyrene (PS) spheres as templates. The magnetic PANI hollow spheres were used as supports for noble metal nanoparticles (NPs) such as Au and Pd. The morphology, composition and magnetic properties of the resulting products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma (ICP) atomic spectra and vibrating sample magnetometer. The catalytic activity of magnetic PANI/Au composite shells on the oxidation of dopamine was investigated by cyclic voltammetry. The obtained results provide our product with a practical application for the detection of dopamine. On the other hand, the catalytic activity of magnetic PANI/Pd composite shells on the reduction of 4-nitroaniline was investigated by spectroscopic methods and compared with Pd/C catalyst which was already widely used in industrial production. [Copyright &y& Elsevier]

Abstract: With an average diameter of 100–150nm, composite nanotubes of polyaniline (PANI)/multiwalled carbon nanotubes (MWNTs) containing Fe3O4 nanoparticles (NPs) were synthesized by a two-step method. First, we synthesized monodispersed Fe3O4 NPs (d=17.6nm, σ=1.92nm) on the surface of MWNTs and then decorated the nanocomposites with a PANI layer via a self-assembly method. SEM and TEM images indicated that the obtained samples had the morphologies of nanotubes. The molecular structure and composition of MWNTs/Fe3O4 NPs/PANI nanotubes were characterized by Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectrometry (EDX), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and Raman spectra. UV–vis spectra confirmed the existence of PANI and its response to acid and alkali. As a multifunctional material, the conductivity and magnetic properties of MWNTs/Fe3O4 NPs/PANI composites nanotubes were also investigated. [Copyright &y& Elsevier]

The successful designing of low‐cost and highly active electrocatalytic materials from earth‐abundant elements are favorable for the large scale production of hydrogen from water splitting. Herein, the controllable sandwiching of reduced graphene oxide (RGO) in hierarchical defect‐rich MoS2 ultrathin nanosheets (MoSGMoS) with vertical alignment and expanded interlayer spacing is synthesized by hydrothermal method. The MoSGMoS product exhibits outstanding electrocatalytic activity for hydrogen evolution reaction (HER) with an onset overpotential of 24.3 mV, low overpotentials of 72 mV at 10 mA cm−2 and 384 mV at 1300 mA cm−2, a small Tafel slope of 44.7 mV decade−1, large exchange current density of 0.67 mA cm−2, and high durability in H2SO4 solution. The HER performance of the MoSGMoS catalyst is much better than most of the reported MoS2‐based catalysts, especially in terms of onset overpotential and cathodic current density. The synergistic effect between defect‐rich MoS2 ultrathin nanosheets with hierarchical structure, vertical alignment and expanded interlayer spacing, and conductive RGO is responsible for the outstanding HER activity. This method may open a new way to grow hierarchical MoS2 nanosheets on carbonaceous materials for enhanced hydrogen production from water splitting. Controllable sandwiching of RGO in hierarchical defect‐rich MoS2 ultrathin nanosheets with vertical alignment and expanded interlayer spacing is synthesized and it exhibits outstanding electrocatalytic activity for hydrogen evolution reaction (HER). The synergistic effect between defect‐rich MoS2 ultrathin nanosheets with hierarchical structure, vertical alignment, and expanded interlayer spacing and conductive RGO is responsible for the outstanding HER activity. [ABSTRACT FROM AUTHOR]

Finding a low-cost, efficient, and stabilized catalyst to accelerate the sluggish oxygen evolution reaction (OER) process, which hinders the production of clean hydrogen energy, is a frontier issue. Here, we synthesized a three-dimensional heterostructure NiSe2 nanoparticle @ FeSe2 microrod (FeSe2/NiSe2) electrocatalyst using a facile one-step hydrothermal method. Compared to single-phase NiSe2 and FeSe2 catalysts, this heterostructured catalyst exhibits an improved OER performance in alkaline electrolyte, that is, a low overpotential of 316 mV and a Tafel slope of 137 mV dec−1 at a current density of 20 mA cm−2 with a long-term durability. Benefitting from a large electrochemical active surface area provided by the specific heterostructure and the modulation of electronic structure at the heterointerface, the OER kinetics of the as-prepared FeSe2/NiSe2 is accelerated. This work may provide a new insight to fabricate a low-cost and efficient heterostructure electrocatalyst for oxygen evolution reaction.Graphical Abstract: Finding a low-cost, efficient, and stabilized catalyst to accelerate the sluggish oxygen evolution reaction (OER) process, which hinders the production of clean hydrogen energy, is a frontier issue. Here, we synthesized a three-dimensional heterostructure NiSe2 nanoparticle @ FeSe2 microrod (FeSe2/NiSe2) electrocatalyst using a facile one-step hydrothermal method. Compared to single-phase NiSe2 and FeSe2 catalysts, this heterostructured catalyst exhibits an improved OER performance in alkaline electrolyte, that is, a low overpotential of 316 mV and a Tafel slope of 137 mV dec−1 at a current density of 20 mA cm−2 with a long-term durability. Benefitting from a large electrochemical active surface area provided by the specific heterostructure and the modulation of electronic structure at the heterointerface, the OER kinetics of the as-prepared FeSe2/NiSe2 is accelerated. This work may provide a new insight to fabricate a low-cost and efficient heterostructure electrocatalyst for oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Visible-light-driven photocatalysis as a green technology has attracted intense interest due to its potential applications in environmental remediation. However, the poor visible light utilization and low electron-hole separation efficiency of photocatalysts largely limited their practical application. In this work, a new ternary visible-light driven photocatalyst of g-C 3 N 4 /CDs/AgBr has been prepared by the introduction of carbon dots (CDs) onto the surface of g-C 3 N 4 , followed by in-situ growth of AgBr nanoparticles on CDs-modified g-C 3 N 4 nanosheets. The g-C 3 N 4 /CDs/AgBr nanocomposite exhibits excellent photocatalytic efficiency for organic pollutant degradation, which is about 4.0, 5.3 and 2.3 times higher than that of AgBr, g-C 3 N 4 and g-C 3 N 4 /AgBr, respectively. The result indicates the introduction of CDs into g-C 3 N 4 /AgBr can largely improve the photocatalytic activity since CDs act as the light absorber and the electron mediator between g-C 3 N 4 and AgBr, which effectively promote the separation of photogenerated charge carriers and the utilization of visible light. Moreover, the photocatalytic activity of g-C 3 N 4 /CDs/AgBr has no obvious decrease after four photodegradation cycles, demonstrating a high photocatalytic stability. This study highlights the potential application of highly efficient CDs decorated photocatalysts in waste water purification. [ABSTRACT FROM AUTHOR]

In this work, an excellent ternary visible-light all solid Z-scheme photocatalytic heterojunction of g-C 3 N 4 /GO/AgBr has been prepared by the attachment of graphene oxide (GO) to the surface of g-C 3 N 4 , followed by in-situ growth of AgBr nanoparticles on GO sheets. The g-C 3 N 4 /GO/AgBr heterojunction exhibits excellent photocatalytic efficiency for RhB degradation, which is about 17.5, 7.9, 3.5, 4.0 and 2.2 times as high as that of P25, g-C 3 N 4 , AgBr, g-C 3 N 4 /GO and g-C 3 N 4 /AgBr heterojunction, indicating the introduction of GO into the system largely improved the capability of the photocatalysis since GO acted as the charge transmission bridge between g-C 3 N 4 and AgBr. Moreover, the photocatalytic performance of g-C 3 N 4 /GO/AgBr just showed a slight decrease after 4 degradation cycles, demonstrating a high stability of the g-C 3 N 4 /GO/AgBr photocatalyst. The photocatalytic mechanism investigation indicated that O 2 − and h + are the major active species in the photocatalytic process. It is expected that the GO-inserted Z-scheme photocatalytic heterojunction could be applied to practical pollutant degradation. [ABSTRACT FROM AUTHOR]

Highlights: [•] SnS2/rGO has been successfully synthesized through a one-pot hydrothermal method. [•] SnS2 nanoflakes along with a small amount of SnS were well decorated on rGO sheets. [•] SnS2 nanoflakes have small sizes of 50–100nm in length and 5–10nm in thickness. [•] The SnS2/rGO nanocomposite showed enhanced adsorption ability for RhB. [ABSTRACT FROM AUTHOR]

Zinc tungstate (ZnWO 4 ) shows great promise as an anode material for lithium-ion batteries (LIBs) owing to its reversible multi-electron redox reactions and high theoretical capacity. Nevertheless, the low conductivity and big strain during cycling can lead to the inferior electrochemical properties of the ZnWO 4 anode, hindering its practical application. Herein, we report a novel composite with ZnWO 4 /ZnO porous nanoplates in-situ constructed on reduced graphene oxide (rGO) by a metal-organic framework template strategy. The nanoplates with good porosity are composed of nanoparticles and nanorods, providing a short Li + -diffusion distance and plentiful Li + storage active sites. The introduction of rGO can accelerate charge transfer and reinforce structural stability. As a result of these advantages, the ZnWO 4 /ZnO/rGO composite as LIBs anode delivers a high reversible capacity of 811 mAh g after 100 cycles at 200 mA g -1 , excellent rate capability (437 mAh g at 5000 mA g -1 ), and good long cycling stability (485 mAh g after 500 cycles at 2000 mA g -1 ). Notably, the rate capability of the composite far precedes the previously reported ZnWO 4 -based anodes. This work provides an efficient approach for designing and fabricating advanced metal tungstate-based anodes for high-performance LIBs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Transition-metal oxides as anodes for lithium-ion batteries (LIBs) have attracted enormous interest because of their high theoretical capacity, low cost, and high reserve abundance. Unfortunately, they commonly suffer from poor electronic and ionic conductivity and relatively large volume expansion during discharge/charge processes, thereby triggering inferior cyclic performance and rate capability. Herein, a molybdenum-zinc bimetal oxide-based composite structure (Zn 2 Mo 3 O 8 /ZnO/rGO) with rectangular Zn 2 Mo 3 O 8 /ZnO nanosheets uniformly dispersed on reduced graphene oxide (rGO) has been prepared by using a simple and controllable cyanometallic framework template method. The Zn 2 Mo 3 O 8 /ZnO rectangular nanosheets with desirable porous features are composed of nanocrystalline subunits, facilitating the exposure of abundant active sites and providing sufficient contact with the electrolyte. Benefiting from the composition and structural merits as well as the induced synergistic effects, the Zn 2 Mo 3 O 8 /ZnO/rGO composite as LIB anodes delivers superior electrochemical properties, including high reversible capacity (960 mA h g -1 after 100 cycles at 200 mA g -1 ), outstanding rate performance (417 mA h g -1 at 10,000 mA g -1 ), and admirable long-term cyclic stability (862 mA h g -1 after 400 cycles at 1000 mA g -1 ). The mechanism of lithium storage and the formation of SEI film are systematically elucidated. This work provides an effective strategy for synthesizing promising Mo-cluster compound-based anodes for high-performance LIBs.