22 research outputs found
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)
Copper nanoparticles coating on FTO with improved adhesion using direct and pulse electrodeposition techniques from a simple copper sulphate solution
Copper (Cu) metal nanoparticles were deposited onto FTO glass using the electrodeposition method. The precursor used was CuSO4 ⋅5H2 O with Na2 SO4 as the inorganic additive. The formation of Cu was characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). This study investigated the impacts of the electrodeposition method (direct electrodeposition vs. pulse electrodeposition), voltages (-0.4 V and -0.8 V), electrodeposition time (60s to 900s) and pulse cycles (50 cycles to 300 cycles), and FTO etching (fixed to 20s etching) towards the morphology and adhesion of Cu deposited. The grain size and thickness of Cu deposited vary with deposition time and pulse cycles. The voltage of -0.4 V successfully deposits shiny, metallic brown Cu onto FTO glass. Meanwhile, the voltage of -0.8 V gives powdery brown Cu on the surface. In addition, compared to direct electrodeposition (DD), pulse electrodeposition (PD) provides a more compact and homogeneous coverage of Cu onto FTO glass. The tape-test results also indicate that FTO etching by electrolysis reduction can improve the adhesion strength between deposited thin Cu film and the FTO glass. This work demonstrates a facile electrodeposition technique with substrate etching as an effective deposition of Cu metal with the potential for application in a wide range of fields
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 CH<sub>4</sub> 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