Statistical modeling and performance optimization of a two-chamber microbial fuel cell by response surface methodology

Microbial fuel cell, as a promising technology for simultaneous power production and waste treatment, has received a great deal of attention in recent years; however, generation of a relatively low power density is the main limitation towards its commercial application. This study contributes toward the optimization, in terms of maximization, of the power density of a microbial fuel cell by employing response surface methodology, coupled with central composite design. For this optimization study, the interactive effect of three independent parameters, namely (i) acetate concentration in the influent of anodic chamber; (ii) fuel feed flow rate in anodic chamber; and (iii) oxygen concentration in the influent of cathodic chamber, have been analyzed for a two-chamber microbial fuel cell, and the optimum conditions have been identified. The optimum value of power density was observed at an acetate concentration, a fuel feed flow rate, and an oxygen concentration value of 2.60 mol m-3, 0.0 m3, and 1.00 mol m-3, respectively. The results show the achievement of a power density of 3.425 W m-2, which is significant considering the available literature. Additionally, a statistical model has also been developed that correlates the three independent factors to the power density. For this model, R2, adjusted R2, and predicted R2 were 0.839, 0.807, and 0.703, respectively. The fact that there is only a 3.8% error in the actual and adjusted R2 demonstrates that the proposed model is statistically significant

Synthesis and Characterization of Alpha-Hematite Nanomaterials for Water-Splitting Applications

The recent momentum in energy research has simplified converting solar to electrical energy through photoelectrochemical (PEC) cells. There are numerous benefits to these PEC cells, such as the inexpensive fabrication of thin film, reduction in absorption loss (due to transparent electrolyte), and a substantial increase in the energy conversion efficiency. Alpha-hematite ([U+F061]-Fe2O3) has received considerable attention as a photoanode for water-splitting applications in photoelectrochemical (PEC) devices. The alpha-hematite ([U+F061]-Fe2O3) nanomaterial is attractive due to its bandgap of 2.1eV allowing it to absorb visible light. Other benefits of [U+F061]-Fe2O3 include low cost, chemical stability and availability in nature, and excellent photoelectrochemical (PEC) properties to split water into hydrogen and oxygen. However, [U+F061]-Fe2O3 suffers from low conductivity, slow surface kinetics, and low carrier diffusion that causes degradation of PEC device performance. The low carrier diffusion of [U+F061]-hematite is related to higher resistivity, slow surface kinetics, low electron mobility, and higher electro-hole combinations. All the drawbacks of [U+F061]-Fe2O3, such as low carrier mobility and electronic diffusion properties, can be enhanced by doping, which forms the nanocomposite and nanostructure films. In this study, all nanomaterials were synthesized utilizing the sol-gel technique and investigated using Scanning Electron Microscopy (SEM), X-ray Diffractometer (XRD), UV-Visible Spectrophotometer (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), Raman techniques, Particle Analyzer, Cyclic Voltammetry (CV), and Chronoamperometry, respectively. The surface morphology is studied by SEM. X-Ray diffractometer (XRD) is used to identify the crystalline phase and to estimate the crystalline size. FTIR is used to identify the chemical bonds as well as functional groups in the compound. A UV-Vis absorption spectral study may assist in understanding electronic structure of the optical band gap of the material. Cyclic voltammetry and chronoamperometry were used to estimate the diffusion coefficient and study electrochemical activities at the electrode/electrolyte interface. In this investigation, the [U+F061]-Fe2O3 was doped with various materials such as metal oxide (aluminum, Al), dichalcogenide (molybdenum disulfide, MoS2), and co-catalyst (titanium dioxide, TiO2). By doping or composite formation with different percentage ratios (0.5, 10, 20, 30) of aluminum (Al) containing [U+F061]-Fe2O3, the mobility and carrier diffusion properties of [U+F061]-hematite ([U+F061]-Fe2O3) can be enhanced. The new composite, Al-[U+F061]-Fe2O3, improved charge transport properties through strain introduction in the lattice structure, thus increasing light absorption. The increase of Al contents in [U+F061]-Fe2O3 shows clustering due to the denser formation of the Al-[U+F061]-Fe2O3 particle. The presence of aluminum causes the change in structural and optical and morphological properties of Al-[U+F061]-Fe2O3 more than the properties of the [U+F061]-Fe2O3 photocatalyst. There is a marked variation in the bandgap from 2.1 to 2.4 eV. The structure of the composite formation Al-[U+F061]-Fe2O3, due to a high percentage of Al, shows a rhombohedra structure. The photocurrent (35 A/cm2) clearly distinguishes the enhanced hydrogen production of the Al-[U+F061]-Fe2O3 based photocatalyst. This work has been conducted with several percentages (0.1, 0.2, 0.5, 1, 2, 5) of molybdenum disulfide (MoS2) that has shown enhanced photocatalytic activity due to its bonding, chemical composition, and nanoparticle growth on the graphene films. The MoS2 material has a bandgap of 1.8 eV that works in visible light, responding as a photocatalyst. The photocurrent and electrode/electrolyte interface of MoS2-[U+F061]-Fe2O3 nanocomposite films were investigated using electrochemical techniques. The MoS2 material could help to play a central role in charge transfer with its slow recombination of electron-hole pairs created due to photo-energy with the charge transfer rate between surface and electrons. The bandgap of the MoS2 doped [U+F061]-Fe2O3 nanocomposite has been estimated to be vary from 1.94 to 2.17 eV. The nanocomposite MoS2-[U+F061]-Fe2O3 films confirmed to be rhombohedral structure with a lower band gap than Al-[U+F061]-Fe2O3 nanomaterial. The nanocomposite MoS2-[U+F061]-Fe2O3 films revealed a more enhanced photocurrent (180 μA/cm2) than pristine [U+F061]-Fe2O3 and other transition metal doped Al-[U+F061]-Fe2O3 nanostructured films. The p-n configuration has been used because MoS2 can remove the holes from the n-type semiconductor by making a p-n configuration. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as the n-type and ND-RRPHTh as the p-type deposited on both n-type silicon and FTO-coated glass plates. The p-n photoelectrochemical cell is stable and allows for eliminating the photo-corrosion process. Nanomaterial-based electrodes [U+F061]-Fe2O3-MoS2 and ND-RRPHTh have shown an improved hydrogen release compared to [U+F061]-Fe2O3, Al-[U+F061]-Fe2O3 and MoS2-[U+F061]-Fe2O3 nanostructured films in PEC cells. By using p-n configuration, the chronoamperometry results showed that 1% MoS2 in MoS2-[U+F061]-Fe2O3 nanocomposite can be a suitable structure to obtain a higher photocurrent density. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as n-type and ND-RRPHTh as p-type showed 3-4 times higher (450 A/cm2) in current density and energy conversion efficiencies than parent electrode materials in an electrolyte of 1M of NaOH in PEC cells. Titanium dioxide (TiO2) is known as one of the most explored electrode materials due to its physical and chemical stability in aqueous materials and its non-toxicity. TiO2 has been investigated because of the low cost for the fabrication of photoelectrochemical stability and inexpensive material. Incorporation of various percentages (2.5, 5, 16, 25, 50) of TiO2 in Fe2O3 could achieve better efficiencies as the photoanode by enhancing the electron concentration and low combination rate, and both materials can have a wide range of wavelength which could absorb light in both UV and visible spectrum ranges. TiO2 doped with [U+F061]-Fe2O3 film was shown as increasing contacting area with the electrolyte, reducing e-h recombination and shift light absorption along with visible region. The [U+F061]-Fe2O3-TiO2 nanomaterial has shown a more enhanced photocurrent (800 μA/cm2) than metal doped [U+F061]-Fe2O3 photoelectrochemical devices

Single-Step Fabrication and Characterization of Nanoscale Cu Thinfilms for Optoelectronic Applications

Nanostructured materials with optical transmittance with sufficient electrical conductivity are feasible for the transparent electrical devices and optoelectronic applications. Copper (Cu) possesses inherent superior electrical conductivity. Cu thin films on glass substrates provide the basic design understanding of the transparent electrodes for humidity sensors and solar cells applications. To understand the fundamental fabrication and electrical properties, a single-step facile fabrication approach was applied for Cu nanofilms through the DC sputtering method. Correlation of thickness of Cu nanofilms with optical and electrical properties was established. Parameters such as current, voltage, vacuum pressure, and time of coating were varied to develop different thickness of metal coating. Under optimized conditions of 10−1 torr vacuum, 1.45 KV voltage, and 4–6 min coating time, a conductive path is successfully established. A 1 min coated sample demonstrated resistance of 4000 ohm and conductance of a 6 min coated sample was raised to 56 m-mho. A higher surge of voltage assisted the production of relatively thick and uniform coatings with the crystallite size of 12 nm. The average coating thickness of 19.8 nm and roughness of 4.5 nm was obtained for a 5 min coated sample through AFM analysis. Further, it was observed that uniform nanostructured coating is essential to establish a mean free path of coated particles

Effect of different micelles on charging and discharging behavior of phase change material

Phase change material (PCM) offers high-density thermal energy storage, making it attractive for thermal management applications of electronic circuitry and thermal energy storage. However, PCM, like paraffin wax, ideal for such low-temperature applications, has very low thermal conductivity. The present study focused on the improvement of the thermal conductivity of paraffin wax using surfactants. The surfactants used as thermal conductivity enhancers (TCE) are cetyltrimethyl ammonium bromide (CTAB), Dioctyl sodium sulfosuccinate (known as AOT) and sodium dodecyl sulfate (SDS). The surfactant self-aggregation called a micelle, acts as conducting medium inside the paraffin wax, providing better thermal conductivity. The highest heat transfer rate with a peak temperature of 71 °C was observed in the case of AOT micelle paraffin wax. Adding SDS, CTAB, and AOT surfactants increased the highest temperatures by 4%, 8.4%, and 18.33% compared to pure PCM

Processing and Characterization of BCZT-Modified BiFeO3-BaTiO3 Piezoelectric Ceramics

The synthesis of non-lead piezoelectric ceramics (1–z)(0.65Bi1.05Fe2O3-0.35BaTiO3)-z Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 using a solid state method and a quenching strategy was investigated. The processing conditions such as the sintering temperature and soaking time were optimized. The patterns of X-ray diffraction (XRD) displayed a pure perovskite structure with no secondary phases. The ferroelectric and piezoelectric characteristics of the samples were considerably improved as a result of the lattice strain. The findings of the experiment revealed that the quenching technique increases the piezoelectric sensor constant of 152 pC/N in optimized conditions. The enhanced piezoelectric sensor constant (d33) value at z = 0.020 was ascribed to the incorporation of multi-cationic BCZT, which modified the bond lengths at a unit cell level and gave rise to more flexibility in complex domain switching. This facilitated easier domain alignment in response to the applied field and resulted in an improvement in the electrical properties

Photoelectrochemical cells

Photoelectrochemical cells including a cathode including alpha-hematite and a metal dichalcogenide, an anode including a conducting polymer, and an electrolyte

p-n Based Photoelectrochemical Device for Water Splitting Application Alpha-Hematite (α-Fe2O3)-Titanium Dioxide (tio2) as N-Electrode & Polyhexylthiophene (rrphth) - Nanodiamond (ND) as P-Electrode

Recently, photoelectrochemical (PEC) water splitting using semiconductor photoanode has received great attention due production of hydrogen through clean energy. The alpha hematite (α Fe2O3) is one of the candidate amongst photoanodic materials, which is chemically stable, abundant in nature with a band gap of 2.0-2. 2eV allowing to be harvesting in the visible light. However, it has also drawn back due to high recombination rate of electron–hole pair revealing the low concentration of charges and lower device performance. In common with α-Fe2O3, the titanium dioxide (TiO2) has been known as one of the most explored photoanode electrode material due to its physical and chemical stability in aqueous and non-toxicity. However, TiO2 has large bandgap (3.0-3.2 eV) that results in absorbing UV light and very small part of visible region. Incorporation of TiO2 in α-Fe2O3 could achieve better efficiencies as photoanode materials by enhancing the electric conductivity, limited hole diffusion length, and both materials can absorb light in both UV and visible spectrum range. However, the photoanodic properties of α-Fe2O3 with different concentrations of TiO2 are mostly unknown. Under this work, α-Fe2O3-TiO2 nanomaterial was synthesized using a hydrothermal method. The α-Fe2O3-TiO2 nanomaterials containing different weight percentage (2.5, 5, 16, 25, and 50) of TiO2 to α-Fe2O3 were characterized using SEM, XRD, UV-Vis, FTIR and Raman techniques, respectively. The electrochemical properties of α-Fe2O3-TiO2 nanomaterials were investigated by cyclic voltammetry and chronoamperometry techniques, respectively

Three-dimensional Heisenberg critical phenomena in La0.6Bi0.1Sr0.3−xCaxMn0.9Cu0.1O3 manganites (x = 0 and 0.05)

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Effect of Binary Oxide Flux on Weld Shape, Mechanical Properties and Corrosion Resistance of 2205 Duplex Stainless Steel Welds

Duplex stainless steel (DSSs) is characterized by excellent corrosion resistance with high strength. Twelve single-component fluxes (TiO2, Fe2O3, Cr2O3, ZnO, ZrO2, CaO, Mn2O3, V2O5, MoO3, SrO, MgO, and LaO2) were tested in the initial experiment using activated Tungsten inert gas (ATIG) technic, and then three couples of oxides were selected as binary fluxes (Fe2O3-Cr2O3, ZnO-Mn2O3, and V2O5-Mn2O3) for the rest of the study. The results show that the depth weld of binary oxides (Fe2O3-Cr2O3, ZnO-Mn2O3) was increased by 3.7 times in comparison with tungsten inert gas (TIG) weld bead. The hardness and the tensile strength of welds carried out with Fe2O3-Cr2O3 and ZnO-Mn2O3 binary fluxes were close to those of the parent metal. Weld bead executed with ZnO-Mn2O3 oxides has more capability to withstand sudden loads. Potentiodynamic polarization tests were performed. The metal welded with flux composed of Fe2O3-Cr2O3 has been found the most resistant to corrosion

Tannic-Acid-Cross-Linked and TiO₂-Nanoparticle-Reinforced Chitosan-Based Nanocomposite Film

A chitosan-based nanocomposite film with tannic acid (TA) as a cross-linker and titanium dioxide nanoparticles (TiO2) as a reinforcing agent was developed with a solution casting technique. TA and TiO2 are biocompatible with chitosan, and this paper studied the synergistic effect of the cross-linker and the reinforcing agent. The addition of TA enhanced the ultraviolet blocking and mechanical properties of the chitosan-based nanocomposite film. The reinforcement of TiO2 in chitosan/TA further improved the nanocomposite film’s mechanical properties compared to the neat chitosan or chitosan/TA film. The thermal stability of the chitosan-based nanocomposite film was slightly enhanced, whereas the swelling ratio decreased. Interestingly, its water vapor barrier property was also significantly increased. The developed chitosan-based nanocomposite film showed potent antioxidant activity, and it is promising for active food packaging