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)

Density functional theory study on the electronic properties of doped-cobalt oxide (CoO)

Cobalt oxide (CoO) has been widely studied for photocatalyst of water splitting and displaying a high-efficiency material. This paper reports a Density Functional Theory (DFT) study on the electronic properties of rock-salt CoO and analyzes effects of cations (Ni and Fe) and anions (N and F) dopants on the electronic properties. For this purpose, CASTEP software used for first principles plane-wave pseudo-potential calculations at different functional, i.e: GGA-PW91 and LDA. The electronic calculations of the CoO optimized structure showed a metallic structure if without considering spin-orbital interactions. After considering the spin-orbital interaction calculation, the CoO band structure possessed indirect and direct band gaps. The direct bandgap by GGA-PW91 calculation is 2.10 eV, it was agreed to the experimentally reported value of approximately 1.9-2.6 eV. Meanwhile, Ni, Fe, and F-doped CoO, demonstrating decreased CoO direct band gaps to 1.70 eV, 1.80 eV, and 1.73 eV, respectively. While N-doped CoO increased the CoO direct bandgap to 3.05 eV. All dopants shifted the conduction and valence bands position, where Ni-doped CoO band edges keep straddle to the redox potential of water splitting. Among other elements in this study, Ni is a more desirable dopant of CoO to enhance photoelectrochemical hydrogen production

Sintesis, pencirian spektroskopi dan sifat fotomangkin Rutenium(II) Bis(bipiridil)-2-(1H-pirazol-3-il)piridil

Kompleks Ru(II), [Ru(bpy)2(pypzH)](PF6)2 dengan bpy = 2,2’-bipiridil dan pypzH= 2-(1H-pirazol-3-il)piridin, telah berjaya disintesis dan dicirikan dengan teknik spektroskopi transformasi Fourier inframerah (FTIR), ultralembayung dan cahaya nampak (UV-Vis), resonans magnet nukleus (RMN), serta spektrometer jisim. Pengiraan dengan kaedah teori fungsi ketumpatan (DFT) dan DFT bersandar masa (TD) telah dijalankan untuk membangunkan struktur optimum dan elektronik kompleks Ru(II). Data yang diperoleh menunjukkan orbital molekul terisi dengan tenaga tertinggi (HOMO) disetempatkan pada logam Ru(II) dan ligan pypzH, manakala orbital molekul tidak terisi dengan tenaga terendah (LUMO) didapati tersebar secara menyeluruh pada kedua-dua struktur ligan bpy. Aktiviti fotomangkin kompleks telah diuji terhadap penguruaian pewarna tekstil bromotimol biru (BTB) disebabkan aktiviti foto [Ru(bpy)2(pypzH)](PF6)2 di bawah sinaran lampu xenon 450W (AM 1.5, penapis inframerah). Kadar dan tertib tindak balas foto-uraian BTB dikenal pasti dan dibincangkan bersama dengan mekanisma foto-uraian BTB

Induced roll magnetic separator applied for high grade ilmenite separation from mining tailing

This article aimed to separate ilmenite (FeTiO3) mineral from tin tailing applying a single splitter IRMS (Induced Roll Magnetic Separator). Ilmenite mineral is the substantial main source for TiO2. This work used air table middling for feeding. The mineral components of middling feeding from air table using grain counting analysis were found as follows: cassiterite (48.61%), ilmenite (21.36%), monazite (18.56%), pyrite (4.60%), zircon (5.85%), quartz (0.71%), anatase (0.27%), and tourmaline (0.02%), It was found that electrical current and opening of single splitter affected the degree of separation addressing to ilmenite recovery and ilmenite grade. The finding showed that current of 15 Ampere and single splitter with opening 4.25 cm yielded ilmenite recovery more than 74%. The high grade ilmenite (90.46 %) and recovery of 29.38% was obtained using 5 Ampere  with single splitter opening of 1.0 cm. Up to date, the study on ilmenite separation from tailing only focused on the effect of current, however, the effect of single splitter magnetic separator  to enhance ilmenite recovery from other paramagnetic minerals such as monazite, siderite, xenotime and tourmaline has not yet been reported.

Synthesis, structure and spectroscopic properties of oxovanadium tris(3,5-dimethylpyrazolyl)borate aroylthiourea complexes

Aroylthiourea ligands, 1-aroyl-3-cyclohexyl-3-methylthiourea (HL1), 1-(2-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL2), 1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3) and 1-(4-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL4) were synthesized through a condensation reaction of methylcyclohexylamine and aroylisothiocyanate with a general formula (X-Ph)(CO)NH(CS)N(C6H5)(CH3) where X = H, o-Cl, m-Cl and p-Cl, fully characterized by CHNS micro elemental analysis, infrared spectroscopy, UV-visible, nuclear magnetic resonance (1H, 13C) and X-ray crystallography. 1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3) crystallized in the monoclinic system, a=14.504(3), b=4.9599(11), c=22.325(5) Å, β=98.461(7)°, Z= 4 and V=1588.5(6) Å with space group P21/c. The IR spectra of the ligands exhibits the characteristic v(CO) and v(N-H) at range 1701-1640 cm-1 and 3317-3144 cm-1, respectively. Whereas the 1H and 13C NMR spectra shows the resonances for N-H and -CO groups at range 8.3-8.5 and 160-163 ppm, respectively. A one-pot reaction involving the aroylthiourea ligand, oxovanadium(IV) ion and potassium hydrotris(3,5-dimethylpyrazolyl)borate (KTp*) complex gave the desired [oxovanadium(IV)(tris(pyrazolyl)borate)(aroylthiourea)] complexes namely Tp*VOL1, Tp*VOL2, Tp*VOL3 and Tp*VOL4 and all complexes were characterized accordingly. X-ray study showed that Tp*VOL1 adopted a monoclinic crystal, a=3.415(2), b=19.463(3), c=14.22(3) Å, β=107.411(4)°, Z= 4 and V=3542.7(11) Å with P21/c space group. The VO2+ center adopted a pseudo-octahedral geometry O2N3S, with the oxovanadium(IV) coordinated to the bidentate ligand (X-Ph)(CO)NH(CS)N(C6H5)(CH3) and tridentate Tp* ligands. The results showed that aroylthiourea ligands behave as bidentate chelate through O and S atom and the Tp* C3v symmetry adds stabilization to the VO2+ through its protective tripodal geometry

Hydrogen production from water splitting using TiO2 /CoS composite photocatalyst

Photocatalytic water splitting reaction has been considered an ideal method for hydrogen generation. In this study, a composite of TiO2 /CoS photocatalyst prepared by hydrothermal synthesis method assisted by ball milling crushing process was used. The TiO2 /CoS composites prepared with three variation compositions of 90/10, 80/20, and 70/30 were named M-10, M-20, and M-30, respectively. Field-emission scanning electron microscopy images showed that the morphologies of the composites were porous and uniform of nanospheres. The X-ray diffraction and energy dispersive spectroscopy analyses confirmed the presence of CoS in the composites. Ultraviolet–visible absorption characterization demonstrated the smallest bandgap value of approximately 2.72 eV presented by sample M-30 with the photocurrent density of 0.32 mA cm−2 at 0.9 V vs. Ag/AgCl. The presence of CoS in this study could increase the PC hydrogen generation of TiO2 by nearly 2.5 times. The composites forming a p-n heterojunction between TiO2 and CoS could prevent electron–hole recombination and increase the overall photoactivity of TiO2.

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

Kesan pemendapan elektroforesis gam arab terhadap kakisan SS316 L dalam persekitaran asid

Keluli tahan karat jenis 316L (SS316L) adalah satu logam yang berpotensi untuk digunakan sebagai plat dwikutub bagi sel fuel membran pertukaran proton (PEMFC). SS316L memiliki sifat kekonduksian elektrik dan kepasifan yang baik, namun jika digunakan pada sekitaran asid (pH 3-6), sifat pelarutan SS316L akan menyebabkan mudah terhakis. Dalam kajian ini, salutan perencat kakisan hijau gam arab dengan kaedah pemendapan elektroforesis (EPD) digunakan untuk mengurangkan kakisan plat SS316L. Hasil analisis scaning electron microscope (SEM) menunjukkan permukaan SS316L lebih halus dan tebal, dengan ketebalan salutan antara 4.9 - 8.9 μm. Pengujian menggunakan kaedah polarisasi linear Tafel dalam media 0.5 M H2 SO4 , mendapati nilai arus kakisan (Icorr) semakin menurun dengan adanya salutan iaitu dari 18.484 μA/cm2 menjadi 0.859 μA/cm2 . Kadar kakisan SS316L tanpa salutan adalah 0.7172 mpy, manakala SS316L yang disalut dengan gam arab mempunyai kadar kakisan yang lebih rendah iaitu 0.033 mpy. Dari kajian ini, keputusan menunjukkan bahawa gam arab dengan salutan EPD dapat memberikan perlindungan kakisan terhadap permukaan SS316L

Effect of external electric field applied to bilayer graphene bandgap: Density Functional Theory Study

Graphene is a prominent material in a wide range of applications, however, the gapless nature of graphene limits its great performance in certain applications, such as in optoelectronic and photocatalytic applications field. Opening the bandgap has become one of the focused studies on graphene material today. Here, we used density functional theory (DFT) calculation to investigate the bandgap opening of bilayer graphene by external electric field applying. The calculation was performed on hexagonal stacked bilayer graphene structure using three different approximations and functional DFT; that is generalized gradient approximation (GGA) PBE and PW-91, as well as Local-density approximations (LDA) -CAPZ. The external electric field varied from 0.0 to 0.5 eV/Å/e in various electric field directions. The calculations results show that the external E-F applied in a perpendicular direction open the bandgap almost 4-times than non-determined the electric field direction. The bandgap opening by LDA functional calculation perform a smaller bandgap opening compared to GGA calculation results, while the PBE and PW-91 of GGA produced similar values at low electric field applied. The larger bandgap of 0.80 eV obtained at 0.3 eV/Å/e electric field applied calculated with both GGA functional At 0.5 eV/Å/e electric field applied, bandgap with GGA-PBE almost zero, and the crystal structure changed from cubic to triclinic with layer position become apart