Ibrahim M.A. Mohamed

Efficiency enhancement of dye-sensitized solar cells by use of ZrO2-doped TiO2 nanofibers photoanode.

Due to the good stability and convenient optical properties, TiO2 nanostructures still the prominent photoanode materials in the Dye Sensitized Solar Cells (DSCs). However, the well-known low bandgap energy and weak adsorption affinity for the dye distinctly constrain the wide application. This work discusses the impact of Zr-doping and nanofibrous morphology on the performance and physicochemical properties of TiO2. Zr-doped TiO2 nanofibers (NFs), with various zirconia content (0, 0.5, 1, 1.5 and 2wt%) were prepared by calcination of electrospun mats composed of polyvinyl acetate, titanium isopropoxyl and zirconium n-propoxyl. For all formulations, the results have shown that the prepared materials are continuous, randomly oriented, and good morphology nanofibers. The average diameter decreased from 353.85nm to 210.78nm after calcination without a considerable influence on the nanofibrous structure regardless the zirconia content. XRD result shows that there is no Rutile nor Brookite phases in the obtained material and the average crystallite size of the sample is affected by the presence of Zr-doping and changed from 23.01nm to 37.63nm for TiO2 and Zr-doped TiO2, respectively. Optical studies have shown Zr-doped TiO2 NFs have more absorbance in the visible region than that of pristine TiO2 NFs; the maximum absorbance is corresponding to the NFs having 1wt% zirconia. The improved spectra of Zr-doped TiO2 in the visible region is attributed to the heterostructure composition resulting from Zr-doping. The absorption bandgaps were calculated using Tauc model as 3.202 and 3.217 for pristine and Zr (1wt%)-doped TiO2 NFs, respectively. Furthermore, in Dye-sensitized Solar Cells, utilizing Zr (1wt%)-doped TiO2 nanofibers achieved higher efficiency of 4.51% compared to the 1.61% obtained from the pristine TiO2 NFs.

ZrO2 nanofibers/activated carbon composite as a novel and effective electrode material for the enhancement of capacitive deionization performance

Among the various forms of carbon materials, activated carbon still possesses the maximum attention as an optimum commercially available, cheap, and effective electrode material for the capacitive deionization desalination process. However, the well-known hydrophobicity and low specific capacitance limit its wide application. In this study, incorporation of zirconia nanofibers with activated carbon is reported as an effective and simple strategy to overcome the abovementioned problems. Typically, zirconia nanofibers, which were synthesized by the calcination of electrospun nanofiber mats, were added to the activated carbon to fabricate novel electrodes for the capacitive deionization units. In a single-mode cell, it was observed that the addition of the proposed metal oxide nanofibers distinctly enhanced the desalination process as the electrosorption capacity and the salt removal efficiency improved from 5.42 to 16.35 mg g−1 and from 16.37% to 53.26% for the pristine and composite electrodes, respectively. However, the inorganic nanofiber content should be optimized; a composite having 10 wt% zirconia nanofibers with respect to the activated carbon showed the best performance. This distinct enhancement in the performance is attributed to the improvement in the wettability and specific capacitance of the electrode. Numerically, the water contact angle and the specific capacitance of the pristine and composite electrodes were found to be 145° and 26.5°, and 875 and 225 F g−1, respectively. Overall, the present study strongly draws attention towards zirconia nanostructures as effective, cheap, environmentally friendly, and biologically safe candidates to enhance the performance of capacitive deionization electrodes.

Cobalt/Chromium Nanoparticles-Incorporated Carbon Nanofibers as Effective Nonprecious Catalyst for Methanol Electrooxidation in Alkaline Medium

Cobalt-Chrome nanoparticles-incorporated carbon nanofibers (CNFs) are proposed as an effective nonprecious electrocatalyst for methanol oxidation in the alkaline media. The introduced nanofibers were prepared by simple technique, electrospinning. Carbonization of as-spun mat composed of chromium acetate, cobalt acetate and poly(vinyl alcohol) (PVA) at high temperature (900∘C) leads to production of the introduced nanofibers. The physicochemical characteristics were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) equipped with EDX and TEM mapping. The exploited analyses confirmed that the final product is in the form of CNFs decorated by Co/Cr nanoparticles. Based on the results obtained from the cyclic voltammetry (CV) measurements, the proposed Co/Cr-incorporated CNFs possess high electrocatalytic activity toward methanol electrooxidation as a clear peak of methanol oxidation appeared with corresponding current density of 56mA/cm2. Moreover, the current density increased by increasing methanol concentration up to 4.0M. Overall, the proposed nanofibers open new avenue for platinum-free and stable nanostructural catalysts for fuel cell technology.

Facile synthesis of TiO 2 /ZrO 2 nanofibers/nitrogen co-doped activated carbon to enhance the desalination and bacterial inactivation via capacitive deionization

Capacitive deionization, as a second generation electrosorption technique to obtain water, is one of the most promising water desalination technologies. Yet; in order to achieve high CDI performance, a well-designed structure of the electrode materials is needed, and is in high demand. Here, a novel composite nitrogen-TiO2/ZrO2 nanofibers incorporated activated carbon (NACTZ) is synthesized for the first time with enhanced desalination efficiency as well as disinfection performance towards brackish water. Nitrogen and TiO2/ZrO2 nanofibers are used as the support of activated carbon to improve its low capacitance and hydrophobicity, which had dramatically limited its adequacy during the CDI process. Importantly, the as-fabricated NACTZ nanocomposite demonstrates enhanced electrochemical performance with significant specific capacitance of 691.78 F g−1, low internal resistance and good cycling stability. In addition, it offers a high capacitive deionization performance of NACTZ yield with electrosorptive capacity of 3.98 mg g−1, and, good antibacterial effects as well. This work will provide an effective solution for developing highly performance and low-cost design for CDI electrode materials.