Ammar Bin Yousaf

Cobalt phosphate nanoparticles decorated with nitrogen-doped carbon layers as highly active and stable electrocatalysts for the oxygen evolution reaction

One promising approach to the production of clean hydrogen energy from electrochemical water splitting mainly relies on the successful development of earth-abundant, highly efficient and stable electrocatalysts for the oxygen evolution reaction (OER). Herein, we report the synthesis of robust cobalt phosphate nanoparticles (NPs) decorated with nitrogen-doped carbon layers (denoted as Co3(PO4)2@N-C) using O-phospho-DL-serine as both phosphate and carbon sources by hydrothermal treatment. The obtained Co3(PO4)2@N-C catalyst exhibits a remarkable electrocatalytic performance for the OER in alkaline media. A current density of 10 mA cm−2 is generated at a overpotential of only 317 mV with a small Tafel slope of 62 mV per decade in 1 M KOH electrolyte, which is even superior to those of state-of-the-art noble metal catalysts such as benchmark IrO2 catalysts. Notably, the Co3(PO4)2@N-C electrode shows excellent stability evaluated by 1000 potential cycles and operation with a high current density at a fixed potential for 8 h, which is highly desirable for a promising electrocatalyst. The excellent activity can be attributed to the unique network structure of materials, a large number of active sites and good conductivity under catalytic conditions. Our findings imply the possibility for the development of robust and cost-efficient cobalt phosphate as a promising candidate to replace high-cost and scarce noble metal catalysts for electrochemical water splitting.

Molybdenum sulfide/graphene-carbon nanotube nanocomposite material for electrocatalytic applications in hydrogen evolution reactions

We report a three-dimensional hierarchical ternary hybrid composite of molybdenum disulfide (MoS2), reduced graphene oxide (GO), and carbon nanotubes (CNTs) prepared by a two-step process. Firstly, reduced GO–CNT composites with three-dimensional microstructuresare synthesized by hydrothermal treatment of an aqueous dispersion of GO and CNTs to form a composite structure via π–π interactions. Then, MoS2 nanoparticles are hydrothermally grown on the surfaces of the GO–CNT composite. This ternary composite shows superior electrocatalytic activity and stability in the hydrogen evolution reaction, with a low onset potential of only 35 mV, a Tafel slope of ~38 mV·decade−1, and an apparent exchange current density of 74.25 mA·cm−2. The superior hydrogen evolution activity stemmed from the synergistic effect of MoS2 with its electrocatalytically active edge-sites and excellent electrical coupling to the underlying graphene and CNT network.

P doped molybdenum dioxide on Mo foil with high electrocatalytic activity for the hydrogen evolution reaction

As a clean and renewable energy carrier, hydrogen generation has attracted much interest and the electrocatalytic hydrogen evolution reaction (HER) is one of the most promising ways of low-cost hydrogen production in the future. In this work, we report the fabrication of noble-metal-free P doped MoO2 nanoparticles (NPs) on Mo foil as electrodes for highly efficient HER. Benefiting from a strong interaction between P doped MoO2 NPs and Mo foil as a current collector, the obtained electrode exhibits excellent HER activity with a small onset overpotential of 80 mV, a large cathodic current density of 10 mA cm−2 at 135 mV and a small Tafel slope of 62 mV per decade, much better than MoO2-based catalysts. Additionally, a P doped MoO2 film/Mo foil electrode displays good stability even after 2000 potential cycles in acidic media. The development of a novel route to prepare P doped MoO2 on Mo foil as an active HER catalyst broadens the insight of designing noble- metal-free HER efficient catalysts with cost-effective and environmentally friendly advantages.

Synergistic effect of graphene and multi-walled carbon nanotubes composite supported Pd nanocubes on enhancing catalytic activity for electro-oxidation of formic acid

The selectivity and sensitivity of a support material can highly improve the catalytic performance of known catalysts. As an excellent electron transfer material and having intercalation characteristics, reduced graphene oxide/multiwalled carbon nanotubes (rGO/MWCNTs) composite provides a synergistic effect on enhancing the electrocatalytic performance of direct formic acid fuel cells. Herein, we report the synthesis of palladium nanocubes (NCs) supported on rGO/MWCNTs composite, rGO and MWCNTs. The electrocatalytic performance for the formic acid oxidation reaction (FAOR) is tested by detailed electrochemical techniques such as cyclic voltametry (CV), chronoamperometery (CA) and electrochemical impedence spectroscopy (EIS) for all supported Pd-NCs catalysts and the results were compared with unsupported Pd-NCs. A significant, systematic and desired improvement in the activity of the FAOR is found for the Pd-NCs/rGO/MWCNTs catalyst. The order of activity is observed to be Pd-NCs < Pd-NCs/MWCNTs < Pd-NCs/rGO < Pd-NCs/rGO/MWCNTs. The results can be attributed to the synergistic effect induced by the hybrid support material on enhancing the activity of the Pd-NCs catalyst.

Synergistic effect of interfacial phenomenon on enhancing catalytic performance of Pd loaded MnOx–CeO2–C hetero-nanostructure for hydrogenation and electrochemical reactions

Hetero-nanostructures have proven to be impressive materials due to their multi-functionalities in various catalytic applications. Here, the basic focus has been devoted to interface chemistry among different domains in the field of catalysis to develop an outstanding composite material with exceptional redox and catalytic properties in hydrogenation and as well in electrochemical reactions. The unique nano-hybrid material is synthesized by the loading of Pd nanoparticles onto MnOx–CeO2 mixed oxides. The heterogeneous catalytic ability for hydrogenation reactions were studied such as the reduction of organic pollutant 4-nitrophenol into 4-aminophenol and the hydrogenation of styrene into ethylbenzene. However, for electrochemical reactions, a comprehensive investigation as anode and cathode materials in direct formic acid fuel cells was performed. The strong reducing property of Pd enhanced the catalytic performance of mixed oxides and the synergistic effect of mixed oxides through interfacial phenomenon improved the performance of the hetero-nanostructured catalyst. The as-designed nanocomposite depicts high catalytic efficiency with low-cost economical standards.

Enhanced and durable electrocatalytic performance of thin layer PtRu bimetallic alloys on Pd-nanocubes for methanol oxidation reactions

As a renewable and promising energy devices, direct methanol fuel cells (DMFCs) have attracted a wide range of interest in recent years. The design of electrocatalysts highly influences the performance of DMFCs systems. Herein, PtRu bimetallic alloy nanoparticles have been fabricated onto a Pd nanocube (NC) core material by a facile wet chemical co-precipitation method. Structural and morphological characterization of the catalyst was performed using X-ray photoelectron spectroscopy (XPS) analysis, energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning TEM (HAADF-STEM) elemental mapping and temperature programmed reduction (TPR). The presence of a single TPR peak strongly supported bimetallic Pt–Ru interactions and alloying. The electrocatalytic performance of the as-synthesized PtRu@Pd-NC catalyst for the methanol oxidation reaction (MOR) is studied in HClO4 aqueous solution by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS), and it is compared with that of a PtRu/C (E-TEK) catalyst. The catalyst has shown the highest specific activity (ca. 11.44 mA cm−2 at 0.70 V), a lower onset potential and enhanced durability for MOR, which is significantly higher than the commercial PtRu/C (E-TEK) catalyst and other reported Pt/Pd-based catalysts. The results attribute to mutual interactions of the core–shell material that enhance the chemisorption of methanol.

INFLUENCE OF PARTICLE SIZE ON DENSITY, ULTRASONIC VELOCITY AND VISCOSITY OF MAGNETITE NANOFLUIDS AT DIFFERENT TEMPERATURES

The influence of particle size on density, ultrasonic velocity and viscosity of magnetite nanofluids have been determined at (298.15 K, 303.15 K, 308.15 K and 313.15 K). Two different sized nanoparticles (commercially procured D = 20–30 nm and synthesized D = 9 ± 3 nm in the laboratory by co-precipitation method) were dispersed in a citric acid base fluid. The desired parameters have been experimentally determined by loading different concentrations of nanoparticles. It has been found that the influence of particle size and temperature on measured physical parameters (density, ultrasonic velocity and viscosity) is not negligible and can also be taken into account in any practical application. The analyzed physical parameters can describe qualitatively and quantitatively the particle size distribution of nanofluids at a specific temperature. Results are interpreted in terms of particle–particle and particle–fluid interactions.

Photoenhanced degradation of methylene blue on polyaniline engineered multiferroics (BiAl0.3Mn0.3Fe0.4O3) nanocomposite systems: a comprehensive study

aGovernment Sadiq College Women University, Bahawalpur, Pakistan, email: farzanawajid67@gmail.com bInstitute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800, Pakistan, Tel/Fax: +86551-3600246; emails: suryyia.manzoor@bzu.edu.pk, suryyia878@gmail.com (S. Manzoor), aamirmirza321@yahoo.com (M. Aamir), naeembzu@bzu.edu.pk (M. NaeemAshiq), ghazalayasmmin@bzu.edu.pk (G. Yasmeen), sana.ijaz@live.com (S. Ijaz), drtariq2000@gmail.com (T.M. Ansari), sajidmalikchem@gmail.com (S. Abbas) cCenter for Advanced Materials, Qatar University, Doha 2713, Qatar, emails: ammar@mail.ustc.edu.cn, ammar.chemist18@gmail.com (A.B. Yousaf)

Synergistic electronic pull of graphene oxide supported Pd nanoparticles on enhancing catalytic activity of electro deposited Pt nanoparticles for methanol oxidation reaction.

USTC fellowship programme offered by University of Science and Technology of China, Hefei and Anhui Government Scholarship offered by Anhui provincial government China.

Characterizaton and Volumetric Studies of Magnetite (Fe3O4) Nanofluids at Different Temperatures

Magnetite nanofluid has been prepared in citric acid based medium. Their stability and polydispersity level have been characterized by UV-visible spectrophotometry.The volumetric properties such as apparent molar volume, partial molar volume and isentropic compressibility of nanofluid have been measured at temperature range from 298.15K to 313.15K at atmospheric pressure. The obtained results were interpreted in terms of particle-particle and particle-fluid interactions, and compared with commercially available magnetite nanofluid in terms of particle size difference. It was observed that the influence of particle size on measured volumetric parameters is significant for any practical applications of fluid flow. The differences in measured quantities were determined qualitatively by considering the state of aggregation / particle size distribution of the nanofluids.