Yahia H. Ahmad

Rational design of porous binary Pt-based nanodendrites as efficient catalysts for direct glucose fuel cells over a wide pH range

The development of porous bi-metallic Pt-based nanocrystals (NCs) as efficient catalysts for the glucose oxidation reaction (GOR) over a wide pH range is still a grand challenge. Triggered by this challenge, we report the controlled synthesis of porous binary PtPd, PtCu, AuPt, and PtNi NCs with open dendritic frames as efficient catalysts for GOR. This was achieved by one-step reduction of their precursors in aqueous solutions of polyvinylpyrrolidone (PVP) under ultrasonic treatment at room temperature. Intriguingly, the porous AuPt and PtPd NCs exhibited the utmost enhancement in GOR activity relative to PtCu, PtNi, and commercial Pt/C catalysts under different pH conditions, which is ascribed to their porous structure and composition. Furthermore, the composition and synergetic effects of the binary metals plausibly generate an activity relationship that tune their catalytic activity and stability in different electrolytes.

An efficient eco advanced oxidation process for phenol mineralization using a 2D/3D nanocomposite photocatalyst and visible light irradiations

Nanocomposites (CNTi) with different mass ratios of carbon nitride (C3N4) and TiO2 nanoparticles were prepared hydrothermally. Different characterization techniques were used including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM) and Brunauer-Emmett-Teller (BET). UV-Vis DRS demonstrated that the CNTi nanocomposites exhibited absorption in the visible light range. A sun light - simulated photoexcitation source was used to study the kinetics of phenol degradation and its intermediates in presence of the as-prepared nanocomposite photocatalysts. These results were compared with studies when TiO2 nanoparticles were used in the presence and absence of H2O2 and/or O3. The photodegradation of phenol was evaluated spectrophotometrically and using the total organic carbon (TOC) measurements. It was observed that the photocatalytic activity of the CNTi nanocomposites was significantly higher than that of TiO2 nanoparticles. Additionally, spectrophotometry and TOC analyses confirmed that degraded phenol was completely mineralized to CO2 and H2O with the use of CNTi nanocomposites, which was not the case for TiO2 where several intermediates were formed. Furthermore, when H2O2 and O3 were simultaneously present, the 0.1% g-C3N4/TiO2 nanocomposite showed the highest phenol degradation rate and the degradation percentage was greater than 91.4% within 30 min.

Controlled design of PtPd nanodendrite ornamented niobium oxynitride nanosheets for solar-driven water splitting

Developing efficient photocatalysts for the water splitting reaction is crucial in a fuel cell reaction. Herein, we present a facile road-map for one-pot fabrication of PtPd nanodendrite (ND) ornamented niobium oxynitride nanosheets (PtPd/NbON) for solar-driven water splitting. This was achieved by annealing Nb2O5 under NH3 to form NbON nanosheets which were subsequently used as starting seeds for the simultaneous growth and self-assembly of PtPd NDs with the assistance of Pluronic F127. The water oxidation performance of PtPd/NbON was substantially superior to those of NbON and Nb2O5. This is ascribed to the combination of NbON with its great visible-light-harvesting properties and narrow band gap and the unique catalytic merits of PtPd NDs.

Highly active, durable and pH-universal hybrid oxide nanocrystals for efficient oxygen evolution

The development of an active, durable, and low-cost catalyst remains hitherto a grand challenge in energy conversion technologies. Herein, hybrid Ptx–NiMnO3 nanocrystals (NCs) (x = 0.1, 0.5, and 1.0 mM) were synthesized by a modified citrate-gel approach and utilized as efficient catalysts towards the oxygen evolution reaction (OER). The results showed that the size of Ptx–NiMnO3 NCs decreases with increasing the initial concentration of Pt. Meanwhile, the OER activity and durability of the as-synthesized Pt–NiMnO3 under different pH conditions are found to be Pt-content-dependent. Particularly, Pt1–NiMnO3 showed superior OER efficiency relative to its counterparts Pt0.5–NiMnO3, Pt0.1–NiMnO3, NiMnO3, and commercial Pt/C at different pH values, ascribed to the size, morphology, and composition effects as confirmed via XRD, XPS and electrochemical characterization.

Enhanced photocatalytic performance of WON@porous TiO2 nanofibers towards sunlight-assisted degradation of organic contaminants

In the last few decades, TiO2 has been widely used in different types of photocatalytic applications. However, the relatively large optical band gap (∼3.2 eV), low charge carrier mobility and consequently its low quantum efficiency limit its photocatalytic activity. Herein, we construct a novel nanostructured heterojunction of WON/TiO2 nanofibers (NFs) by integration of TiO2 nanofibers synthesized by electrospinning of a polymer solution containing a titanium(IV) butoxide precursor with WON nanoparticles fabricated via annealing of a WO3 precursor in dry ammonia at 700 °C. The synthesized photocatalysts were characterized using different spectroscopic techniques. Their photocatalytic performance towards the degradation of methyl orange, methylene blue, and phenol as model contaminants was investigated and the charge transfer process was elucidated and compared to that of a TiO2/WO3 heterojunction.

Metal Matrix Composite Coatings of Cupronickel Embedded with Nanoplatelets for Improved Corrosion Resistant Properties

The deterioration of metals under the influence of corrosion is a costly problem faced by many industries. Therefore, particle-reinforced composite coatings are being developed in different technological fields with high demands for corrosion resistance. This work studies the effects of nanoplatelet reinforcement on the durability, corrosion resistance, and mechanical properties of copper-nickel coatings. A 90 : 10 Cu-Ni alloy was coelectrodeposited with nanoplatelets of montmorillonite (Mt) embedded into the metallic matrix from electrolytic baths containing 0.05, 0.10, and 0.15% Mt. X-ray diffraction of the coatings indicated no disruption of the crystal structure with addition of the nanoplatelets into the alloy. The mechanical properties of the coatings improved with a 17% increase in hardness and an 85% increase in shear adhesion strength with nanoplatelet incorporation. The measured polarization resistance increased from 11.77 kΩ·cm2 for pure Cu-Ni to 33.28 kΩ·cm2 for the Cu-Ni-0.15% Mt coating after soaking in a simulated seawater environment for 30 days. The incorporation of montmorillonite also stabilized the corrosion potential during the immersion study and increased resistance to corrosion.