Density Functional Theory Studyof Water Adsorption on the CoO (100) and CoO (110) Surfaces

The density functional theory (DFT) method was used in this study to determine the chemical and physical properties of Cobalt Oxide (CoO) because it is a reliable, fast and inexpensive technique. This study is designed to determine the electronic properties of CoO bulk and the adsorption energy of the water molecule (H2O) on the CoO surface. CoO crystals used in this study have been optimized by using the GGA-PBE and LDA-CAPZ methods. The study found that calculations using GGA-PBE were closer to the experiment value. Without considering spin orbital interactions, CoO showed a metallic electronic band structure. After considering the spin orbital interaction calculation, each alpha and beta band structures has band gap of 1.55 eV, which is similar to the reported theoretical value. The ground state of CoO is antiferromagnetic base-on alpha and beta band structures. The peak absorption of light representing optical properties at wavelength energy is 351 nm in visible light spectrum (UV) range. The DFT calculation is used to determine the H2O adsorption energy to the surfaces of CoO (100) and CoO (110). H2O adsorption energy on CoO (100) and CoO (110) surfaces is based on eight different configurations, with different H2O adsorption positions on each CoO surface. On the CoO (100) surface, H2O adsorption energy is optimum in Model 5, with a value of 5.123 eV. Meanwhile, the H2O adsorption energy on the CoO (110) surface is optimum in Model 6, with a value of 2.810 eV. Based-on adsorption energy study, it expected that H2O easier to absorb on CoO(110) rather than on CoO(100)

Synthesis of graphene/Cu2O thin film photoelectrode via facile hydrothermal method for photoelectrochemical measurement

The process of carbon dioxide (CO2) reduction by using efficient non-precious-metal catalyst to make the process be economical has brought a comprehensive research in the area. In this study, graphene layer in copper foil was easily synthesized using hydrothermal method at temperature 200°C in 3 h duration. Diffraction peaks in XRD at around 29°, 36°, 42° and 74° in the composites correlate to the (110), (111), (200) and (311) crystalline planes of cubic cuprous oxide (Cu2O), while peak at 27° showed the carbon graphitic peak. Raman confirms the presence of the graphene layer on Cu2O. Photoelectrochemical performance test of Graphene/Cu2O demonstrated that the photoelectrocatalyst showing the photocurrent density 9.6 mA cm-2 at -0.8V vs Ag/AgCl. This study demonstrated a potential of semiconductor-based hybrid electrode for an efficient photoelectrocatalytic of CO2 reduction

3D Free-standing graphene: influence of etching solution and etching time on chemical vapor deposition on the graphene/nickel foam

Three-dimensional (3D) structures made of graphene sheets have been developed recently, and have resulted in the development of a new class of graphene materials known as 3D graphene materials. High-quality free-standing 3D graphene foam has been synthesized by chemical vapor deposition (CVD) on nickel foam followed by a chemical etching process to remove the nickel foam as a template. Field-emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and Raman spectroscopy measurements were performed to investigate the morphologies, crystal phase, and the structure of nickel foam (NF), graphene/nickel foam (Gr/NF), and 3D graphene (3D Gr). In this study, the influence of etching solution and etching time on Gr/NF to produce free-standing 3D Gr was investigated. XRD spectroscopy showed that the mixed solutions of 1M FeCl3:1M HCl at 80 °C for 3 h can significantly remove the NF and no peaks of NF are observed, thus indicating a high crystal quality of 3D Gr was obtained. In addition, XRD spectroscopy revealed that by increasing the etching time beyond 3 h, the intensity of diffraction peaks decreases, thus degrading graphene quality. This research emphasizes the significance of proper selections of etching solution and etching time in removing the NF to maintain the characteristic, quality, and surface morphology of 3D Gr after the etching process

Aplikasi keluli tahan karat sebagai elektrod logam di dalam sistem bioelektrokimia

Kertas kerja ini meninjau akan penggunaan dan prestasi terkini beberapa jenis logam sebagai elektrod dalam pembangunan sistem bioelektrokimia (BES) termasuk sel bahan api mikrob (MFC) dan sel elektrolisis mikrob (MEC). Elektrod konvensional yang berasaskan karbon biasanya digunakan sebagai anod atau katod disebabkan struktur bahan berliang dan paling sesuai untuk pertumbuhan bakteria aktif elektrokimia (EAB). Walau bagaimanapun, perkembangan baru menunjukkan penggunaan elektrod logam mampu menghasilkan ketumpatan arus yang lebih tinggi dan kuasa maksimum daripada karbon, kerana sifat-sifat logam seperti kekonduksian yang tinggi dan kekuatan mekanikal, anti-karat serta kestabilan struktur kimia. Strategi pengubahsuaian permukaan logam menggalakkan perlekatan EAB serta meningkatkan tahap biokompatibiliti atau pemindahan elektron di antara sel bakteria dan elektrod. Di samping itu, kos efektif serta mudah beroperasi untuk jangka masa panjang merupakan faktor penyumbang kepada penggunaan elektrod logam. Dari kajian yang dijalankan sehingga kini, keluli tahan karat merupakan logam yang sering digunakan dalam pembangunan BES

Electrochemical characterisation of heat-treated metal and non-metal anodes using mud in microbial fuel cell

Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity generation. However, the choice of the electrode material and its design is critical and directly affect their performance. As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF) was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs. The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2 and 827.25 mW/m2, respectively, which were higher than MFC-CS (641.95 mA/m2 and 260.14 mW/m2) and MFC-GF (728.30 mA/m2 and 307.89 mW/m2). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and MFC-GF anode, also supported by cyclic voltammetry test

Magnetite (Fe3O4) Nanoparticles in Biomedical Application: From Synthesis to Surface Functionalisation

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 the MNP properties, 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

Electrodeposited WO3/Au photoanodes for photoelectrochemical reactions

This work aims to study the effect of gold (Au) loading on the photoelectrochemical behavior of tungsten trioxide (WO3 ) photoelectrodes. The WO3 film has been fabricated via electrodeposition method with constant potential on fluorine doped tin oxide (FTO) glass substrate. The Au nanoparticle loading on WO3 films surface was also prepared by constant potential electrodeposition. Due to the small amount of Au loading, the band gap values of the plasmonized WO3 remained around 2.6 eV. However, during the photoelectrochemical analysis, the photoactivity of the plasmonized WO3 photoelectrodes improved >100% with a minimal amount of Au loading compared to the pristine WO3 . The photocurrent generation was further enhanced with the presence of organic donors (methanol and formic acid). The photocurrent achieved 3.74 mA/cm2 when 1.0 M of formic acid was added. Plausible charge transfer mechanism was suggested

Formation of Oriented Graphene Nanoribbons over Heteroepitaxial Cu Surfaces by Chemical Vapor Deposition

We demonstrate a new bottom-up approach to synthesize graphene nanoribbons (GNRs) on a Cu(100) film by chemical vapor deposition (CVD) without the use of any lithography and etching processes. Ambient pressure CVD with a low concentration CH₄ feedstock produced a number of GNRs with widths of 40–50 nm on a heteroepitaxial Cu(100)/MgO(100) substrate. These nanoribbons are confined inside the nanoscale trenches formed on the Cu surface, and their orientations are highly controlled by the crystallographic orientation of the Cu(100) lattice. Raman spectra taken after the transfer indicated the growth of high-quality, single-layer GNRs. Moreover, low-energy electron microscopy revealed that all these aligned GNRs have the hexagonal orientations whose edges are terminated with zigzag edges. The GNR growth was not observed on Cu foil, and we discuss the growth mechanism of the oriented GNRs over epitaxial Cu(100) film. Our bottom-up approach offers a new method to grow single-layer GNRs which are oriented in a specific directions for future carbon-based nanoelectronics and spintronics applications

Enhancing Photoluminescence Intensity and Spectral Bandwidth of Hybrid Nanofiber/Thin-Film Multilayer Tm3+-Doped SiO2–HfO2

Multilayering of optical thin films is widely used for a range of purposes in photonic technology, but the development of nanofiber structures that can outperform thin films and nanoparticles in optical applications cannot simply be disregarded. Hybrid structures composed of Tm3+-doped SiO2–HfO2 in the form of nanofibers (NFs) and thin films (TFs) are deposited on a single substrate using the electrospinning and dip-coating methods, respectively. Ultrafine nanofiber strands with a diameter of 10–60 nm were fabricated in both single and multilayer samples. Enhanced photoluminescence emission intensity of about 10 times was attained at wavelengths of around 457, 512 and 634 nm under an excitation of 350 nm for NF-TF-NF* hybrid structures when compared with single-layered NF and TF structures. The arrangement of nanofibers and thin films in a multilayer structure influenced the luminescence intensity and spectral bandwidth. High transparency in the range of 75–95% transparency across the wavelength of 200–2000 nm was achieved, making it ideal for photonic application. Theoretical findings obtained through IMD software were compared with experimental results, and they were found to be in good agreement