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Photoelectrochemical (PEC) technology is a promising strategy that can directly convert sunlight into chemical energy. Direct solar water splitting through the PEC process is a desirable method for green hydrogen (H2) production. This technology has also the potential to capture CO2 and convert it into fuels using sunlight and water, besides converting N2 and H2O to produce ammonia (NH3), which acts as transportable H2 storage. The cracking of NH3 to produce H2 can also be accomplished using PEC technology. Despite improved PEC performance having been shown, stability, efficiency, and scalability issues still need to be resolved. Even so, PEC technology has much potential as a clean and sustainable solution for addressing global energy and environmental challenges. [ABSTRACT FROM AUTHOR]

Two-dimensional materials have attracted intensive attention recently due to their unique optical and electronic properties and their promising applications in water splitting and solar cells. As a representative layer-structured of transition metal dichalcogenides, MoS2 has attracted considerable devotion owing to its exceptional photo and electro properties. Here, we show that the chemical vapour deposition (CVD) growth of MoS2 on Si photocathode and graphene/Si photocathode can be used to prepare photoelectrocatalysts for water splitting. We explore a bottom‐up method to grow vertical heterostructures of MoS2 and graphene by using the two‐step CVD. Graphene is first grown through ambient-pressure CVD on a Cu substrate and then transferred onto SiO2/Si substrate by using the chemical wet transfer followed by the second CVD method to grow MoS2 over the graphene/SiO2/Si. The effect of the growth temperatures of MoS2 is studied, and the optimum temperature is 800 °C. The MoS2 produced at 800 °C has the highest photocurrent density at −0.23 mAcm−2 in 0.5 M Na2SO4 and −0.51 mAcm−2 in 0.5 M H2SO4 at −0.8 V versus Ag/AgCl. The linear sweep voltammetry shows that MoS2 in 0.5 M H2SO4 has about 55% higher photocurrent density than MoS2 in Na2SO4 due to the higher concentration of protons (H+) in the H2SO4 electrolyte solution. Protons are reduced to H2 at lower overvoltage and hydrogen generation is thus enhanced at higher photocurrent density. MoS2/graphene/SiO2/Si (MGS) has −0.07 mAcm−2 at −0.8 V versus Ag/AgCl of photocurrent density, which is 70% lower than that of bare MoS2 because MGS is thicker compared with MoS2. Thus, MoS2 has potential as a photocatalyst in photoelectrochemical water splitting. The structure and the morphology of MoS2 play an important role in determining the photocurrent performance. [ABSTRACT FROM AUTHOR]

Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, chemical stability, innocuousness, high saturation magnetisation, and inexpensiveness. Magnetite (Fe3O4) exhibits superparamagnetism as its size shrinks in the single-domain region to around 20 nm, which is an essential property for use in biomedical applications. In this review, the application of magnetite nanoparticles (MNPs) in the biomedical field based on different synthesis approaches and various surface functionalisation materials was discussed. Firstly, a brief introduction on theMNPproperties, such as physical, thermal, magnetic, and optical properties, is provided. Considering that the surface chemistry of MNPs plays an important role in the practical implementation of in vitro and in vivo applications, this review then focuses on several predominant synthesis methods and variations in the synthesis parameters of MNPs. The encapsulation of MNPs with organic and inorganic materials is also discussed. Finally, the most common in vivo and in vitro applications in the biomedical world are elucidated. This review aims to deliver concise information to new researchers in this field, guide them in selecting appropriate synthesis techniques for MNPs, and to enhance the surface chemistry of MNPs for their interests. [ABSTRACT FROM AUTHOR]

Summary: Reduced graphene oxide (RGO) has progressed as one of key emerging carbon for catalyst support material. As an alternative to the conventional RGO precursor, biomass Sengon wood was converted into RGO for use as a noble metal free catalyst support in oxygen reduction reaction (ORR). This work intends to reveal the applicability of Sengon wood‐derived RGO in anchoring/doping iron and nitrogen particles onto its surface and to study its ORR performance in a half‐cell environment. Thin‐sheet layer and highly defective (ID/IG) was gradually obtained at elevated pyrolysis temperature of Sengon wood graphene oxide (GO) at range 700°C to 900°C. As prepared RGO was further doped into catalyst (Fe/N/RGO) through the same pyrolysis procedure at a selected temperature after mixing the GO powder with iron chloride and different nitrogen precursors (urea, choline chloride, and polyaniline) at a fixed ratio. The ORR activity reached a current density up to 2.43 mA/cm2, which in conjunction with smooth multilayer sheet morphology and high graphitic‐N content as the active sites. Stability analysis indicated an 85% current efficiency and only 0.03 V reduction in onset potential on methanol resistant test for Fe/ChoCl/RGO catalyst. This study revealed that Sengon wood‐derived RGO successfully supported Fe‐N‐C catalyst which showed comparable oxygen reduction activity to Pt/C. [ABSTRACT FROM AUTHOR]

Perfluorosulphonic acid-based membranes such as Nafion are widely used in fuel cell applications. However, these membranes have several drawbacks, including high expense, non-eco-friendliness, and low proton conductivity under anhydrous conditions. Biopolymer-based membranes, such as chitosan (CS), cellulose, and carrageenan, are popular. They have been introduced and are being studied as alternative materials for enhancing fuel cell performance, because they are environmentally friendly and economical. Modifications that will enhance the proton conductivity of biopolymer-based membranes have been performed. Ionic liquids, which are good electrolytes, are studied for their potential to improve the ionic conductivity and thermal stability of fuel cell applications. This review summarizes the development and evolution of CS biopolymer-based membranes and ionic liquids in fuel cell applications over the past decade. It also focuses on the improved performances of fuel cell applications using biopolymer-based membranes and ionic liquids as promising clean energy [ABSTRACT FROM AUTHOR]

Heterostructures of two-dimensional (2D) layered materials have attracted growing interest due to their unique properties and possible applications in electronics, photonics, and energy. Reduction of the dimensionality from 2D to one-dimensional (1D), such as graphene nanoribbons (GNRs), is also interesting due to the electron confinement effect and unique edge effects. Here, we demonstrate a bottom-up approach to grow vertical heterostructures of MoS2 and GNRs by a two-step chemical vapor deposition (CVD) method. Single-layer GNRs were first grown by ambient pressure CVD on an epitaxial Cu(100) film, followed by the second CVD process to grow MoS2 over the GNRs. The MoS2 layer was found to grow preferentially on the GNR surface, while the coverage could be further tuned by adjusting the growth conditions. The MoS2/GNR nanostructures show clear photosensitivity to visible light with an optical response much higher than that of a 2D MoS2/graphene heterostructure. The ability to grow a novel 1D heterostructure of layered materials by a bottom-up CVD approach will open up a new avenue to expand the dimensionality of the material synthesis and applications. [ABSTRACT FROM AUTHOR]

ZnO nanorods (NRs) were synthesized hydrothermally on a pre‐seeded graphene/nickel foam (NF) substrate. The effects of concentration on the photoelectrochemical (PEC) cell performance and hydrothermal reaction were studied. The field emission scanning electron microscopy images revealed that the precursor concentrations influenced the shape of the ZnO NRs on graphene/NF (ZGN). The X‐ray diffraction pattern for hexagonal wurtzite demonstrated strong orientation along the (002) direction. Notably, compared with the other concentrations, 0.04 M ZGN exhibited the highest photocurrent density, which was attributed to the optimal diameter and length of the rods for efficient light absorption. This research showed enhanced PEC performance, compared with existing literature, emphasizing the exceptional quality of the produced ZGN. [ABSTRACT FROM AUTHOR]

Abstract: The physical and electrochemical properties of the activated carbon pellet electrodes have been investigated. Activated carbon pellets were prepared from single step carbonization process of pre-carbonized rubber wood sawdust at a temperature of 800°C that followed with a CO2 activation process at temperature in the range of 700–1000°C. The BET characterization on the sample found that the surface area of the carbon pellet increased with the increasing of the activation temperature. The optimum value was as high as 683.63m2 g−1. The electrical conductivity was also found to increase linearly with the increasing of the activation temperature, namely from 0.0075Scm−1 to 0.0687Scm−1 for the activation temperature in the range of 700–1000°C. The cyclic voltammetry characterization of the samples in aqueous solution of 1M H2SO4 also found that the specific capacitance increased with the increasing of the activation temperature. Typical optimum value was shown by the sample activated at 900°C with the specific capacitance was as high as 33.74Fg−1 (scan rate 1mVs−1). The retained ratio was as high as 32.72%. The activated carbon pellet prepared from the rubber wood sawdust may found used in supercapacitor applications. [Copyright &y& Elsevier]

The presence of grain boundaries in two-dimensional (2D) materials is known to greatly affect their physical, electrical, and chemical properties. Given the difficulty in growing perfect large single-crystals of 2D materials, revealing the presence and characteristics of grain boundaries becomes an important issue for practical applications. Here, we present a method to visualize the grain structure and boundaries of 2D materials by epitaxially growing transition metal dichalcogenides (TMDCs) over them. Triangular single-crystals of molybdenum disulfide (MoS2) epitaxially grown on the surface of graphene allowed us to determine the orientation and size of the graphene grains. Grain boundaries in the polycrystalline graphene were also visualized reflecting their higher chemical reactivity than the basal plane. The method was successfully applied to graphene field-effect transistors, revealing the actual grain structures of the graphene channels. Moreover, we demonstrate that this method can be extended to determine the grain structure of other 2D materials, such as tungsten disulfide (WS2). Our visualization method based on van der Waals epitaxy can offer a facile and large-scale labeling technique to investigate the grain structures of various 2D materials, and it will also contribute to understand the relationship between their grain structure and physical properties.