Papers by Author: Amir Al-Ahmed

Abstract: One critical component in a vanadium redox flow battery (VRFB) system is its electrode. The redox reactions between V⁺²/V⁺³ and V⁺⁴/V⁺⁵ take place on electrodes surfaces. Commonly used electrode material is the graphite felts (GFs); this material has good chemical and electrochemical stabilities, conductivity, and suitable surface area, with low price tag. However, its relatively poor kinetics and electrochemical activity often limit the VRFB operation at low current density. Many researchers have attempted to enhance VRFB performance by trying other carbon materials such as, carbon nanotubes, graphene, and composite materials. They also deposited noble metals on to these electrodes as catalysts, which are not very practical due to their high cost and susceptibility to hydrogen/oxygen evolution reactions. Low-cost metal oxides, such as Mn₃O₄, CeO₂ and WO₃ were also been explored as catalysts, but their performance is limited by their low conductivity and stability in concentrated sulfuric acid. Significant improvement in electrode performance are reported when different nanostructured metal catalysts were deposited. However, the performance of modified electrodes also depends on the size and uniform distribution of these nanoparticles. In this article, some important developments of this area are reviewed.

Abstract: Hydrogen is the lightest and most abundant element in the universe and an energy carrier. It can be produced from several sources using various methods, such as, electrolysis of water or reforming of hydrocarbons like, natural gas can produce hydrogen in a big plant or fuelling stations. When it is produced using renewable energy sources such as wind, solar, geothermal, or hydroelectric power, it supports the zero emissions approach. Hydrogen powdered electricity generation, whether it is for vehicles, or others, it can be carried out mainly in two ways: burning hydrogen in an internal combustion engine, or reacting hydrogen with oxygen in a fuel cell. Above all, we need to have proper storage facility available at the production and as well as at the utilization site. There are several hydrogen storage technology available such as compressed storage; liquid hydrogen storage; metal hydrides, chemical hydride and by sorption in some porous medium. In this review article, some of the important finding in hydrogen storage materials for physical absorption methods has been discussed.

Abstract: Electrically conducting polymers (ECPs) are finding applications in various fields of science owing to their fascinating characteristic properties such as binding molecules, tuning their properties, direct communication to produce a range of analytical signals and new analytical applications. Polyaniline (PANI) is one such ECP that has been extensively used and investigated over the last decade for direct electron transfer leading towards fabrication of mediator-less biosensors. In this review article, significant attention has been paid to the various polymerization techniques of polyaniline as a transducer material, and their use in enzymes/biomolecules immobilization methods to study their bio-catalytic properties as a biosensor for potential biomedical applications.

Abstract: Greenhouse gases such as CO₂, CH₄ and CFCs are the primary causes of global warming. Worldwide, people are exploring techniques to reduce, capture, store CO₂ gas and even convert this gas in to some useful chemicals. CO₂ can be transformed into hydrocarbons in a photocatalytic reaction. The advantage of photo reduction of CO₂ is to use inexhaustible solar energy. Knowledge of elementary steps in photocatalytic CO₂ reduction under UV irradiation is required in order to improve the photo efficiency of the photocatalyst. A semiconductor photocatalyst mediating CO₂ reduction and water oxidation needs to absorb light energy, generate electron hole pairs, spatially separate them, transfer them to redox active species across the interface and minimize electron hole recombination. This requires the semiconductor to have its conduction band electrons at higher energy compared to the CO₂ reduction potential while the holes in the valence band need to be able to oxidize water to O₂. A single semiconductor does not usually satisfy these requirements. Some recent developments in this field have been moves towards rational photocatalyst design, the use of highly active isolated Ti-species in mesoporous and microporous materials, metal-doping of TiO₂, development of catalysts active at longer wavelengths than can be achieved with commercially available titania etc. The use of transition-metal loaded titanium dioxide (TiO₂) has been extensively studied as a photocatalyst in photoreactions. Unlike traditional catalysts drive chemical reactions by thermal energy, semiconducting photocatalysts can induce chemical reactions by inexhaustible sunlight and convert CO₂ in to the useful hydrocarbons. In this review article we will cover different aspects of metal doped nano structured TiO₂ photocatalysts, used to convert/reduce CO₂ in to useful hydrocarbons.

Abstract: Tremendous amount of research work is going on Titanium dioxide (TiO₂) based materials. These materials have many useful applications in our scientific and daily life and it ranges from photovoltaics to photocatalysis to photo-electrochromics, sensors etc.. All these applications can be divided into two broad categories such as environmental (photocatalysis and sensing) and energy (photovoltaics, water splitting, photo-/electrochromics, and hydrogen storage). Synthesis of TiO₂ nanoparticles with specific size and structural phase is crucial, for solar sell application. Monodispersed spherical colloids with minimum size variation (5% or less) is essential for the fabrication of photonic crystals. When sensitized with organic dyes or inorganic narrow band gap semiconductors, TiO₂ can absorb light into the visible light region and convert solar energy into electrical energy for solar cell applications. TiO₂ nanomaterials also have been widely studied for water splitting and hydrogen production due to their suitable electronic band structure given the redox potential of water. Again nanostructured TiO₂ has extensively been studied for hydrogen storage with good storage capacity and easy releasing procedure. All these issues and related finding will be discussed in this review.