Direct Alcohol Fuel Cells: A Comparative Review of Acidic and Alkaline Systems

In the last 20 years, direct alcohol fuel cells (DAFCs) have been the subject of tremendous research efforts for the potential application as on-demand power sources. Two leading technologies respectively based on proton exchange membranes (PEMs) and anion exchange membranes (AEMs) have emerged: the first one operating in an acidic environment and conducting protons; the second one operating in alkaline electrolytes and conducting hydroxyl ions. In this review, we present an analysis of the state-of-the-art acidic and alkaline DAFCs fed with methanol and ethanol with the purpose to support a comparative analysis of acidic and alkaline systems, which is missing in the current literature. A special focus is placed on the effect of the reaction stoichiometry in acidic and alkaline systems. Particularly, we point out that, in alkaline systems, OH- participates stoichiometrically to reactions, and that alcohol oxidation products are anions. This aspect must be considered when designing the fuel and when making an energy evaluation from a whole system perspective

Addressing scale-up challenges and enhancement in performance of hydrogen-producing microbial electrolysis cell through electrode modifications

Bioelectrohydrogenesis using a microbial electrolysis cell (MEC) is a promising technology for simultaneous hydrogen production and wastewater treatment which uses electrogenic microbes. Microbial activity at the anode and hydrogen evolution reaction at the cathode can be controlled by electrode–microbe interaction and electron transfer. The selection of anode electrode material is governed by electrochemical oxidation of substrates and subsequent electron transfer to the anode. Similarly, a good cathodic material should reduce the overpotential at the cathode and enhance the hydrogen evolution reaction and H2 recovery. This review mainly focused on modifications in electrode materials and cheaper novel alternatives to improve the performance for MEC and overcome its scale-up challenges for practical applications. Performance of various anode and cathode materials based on Ni alloys, stainless steel, polyaniline, palladium, and carbon has been discussed. The scalability of the material should consider its inexpensive fabrication procedure and efficiency. NPRP grant NPRP12S-0304-190218 from the Qatar National Research Fund (a member of Qatar Foundation)

Three-dimensional nanotube arrays for solar energy harvesting and production of solar fuels

Over the past decade extensive research has been carried out on photovoltaic semiconductors to provide a solution towards a renewable energy future. Fabricating high-efficiency photovoltaic devices largely rely on nanostructuring the photoabsorber layers due to the ability of improving photoabsorption, photocurrent generation and transport in nanometer scale. Vertically aligned, highly uniform nanorods and nanowire arrays for solar energy conversion have been explored as potential candidates for solar energy conversion and solar-fuel generation owing to their enhanced photoconversion efficiencies. However, controlled fabrication of nanorod and especially nanotube arrays with uniform size and shape and a pre-determined distribution density is still a significant challenge. In this research work, we demonstrate how to address this issue by fabricating nanotube arrays by confined electrodeposition on lithographically patterned nanoelectrodes defined through electron beam as well as nanosphere photolithography. This simple technique can lay a strong foundation for the study of novel photovoltaic devices because successful fabrication of these devices will enhance the ability to control structure-property relationships. The nanotube patterns fabricated by this method could produce an equivalent amount of photocurrent density produced by a thin film like device while having less than 10% of semiconducting material coverage. This project also focused on solar fuel generation through photoelectrocatalytic water splitting for which efficient electrocatalysts were developed from non-precious elements. Lastly, a protocol was developed to disperse these electrocatalysts into a butadiene based polymeric catalytic ink and further processing to yield free-standing catalytic film applicable for water electrolysis”--Abstract, page iv

Electrochemical Development of Cathode for Metal Supported-Solid Oxide Fuel Cells

In comparison to conventional generation systems, the use of Solid Oxide Fuel Cells (SOFCs) provides higher electrical efficiency and lower carbon emissions. Furthermore, contrary to other fuel cell types, SOFC is considered fuel flexible as it can use a variety of fuels, such as hydrogen, alcohol, natural gas and other hydrocarbons or syngas. Nevertheless, SOFCs is expensive in terms of fabrication cost, as it is made essentially of advanced ceramic materials because of its high operating temperature (600-900°C). Much effort has been devoted to reduce cost, one possibility being the use of metal-supported solid oxide fuel cell (MS-SOFC). Cost reduction with MS-SOFC takes place because cheaper metal materials can replace some ceramic ones. Indeed, in MS-SOFC, the supporting structure is made of porous metal, on which are deposited thin ceramic layers for the anode, electrolyte and cathode. In traditional SOFC, one of those ceramic layers (typically the anode) is made thicker to support the whole assembly. Besides cost, there are other important advantages in using MS-SOFCs as they possess high oxidation resistance, mechanical stability and tolerance to redox cycles. On the other hand, there are important challenges in the fabrication of MS-SOFC as very high temperatures are involved to make dense electrolyte, which normally is done in air, but not in the present case to avoid extensive oxidation of the metal at those high temperatures (above 1200°C). Another constraint is that the coefficient of thermal expansion (CTE) of the porous metal support must match the CTE of the ceramic materials, such as yttrium stabilized zirconia (YSZ), typically used as electrolyte. The fabrication method considered in this work is tape casting of different layers followed by co-sintering (under reducing atmosphere). In this thesis, SS-430 L and YSZ have been used as metal support and electrolyte, respectively. However, the main focus of this study is on the cathode, for which two different types of cathode material/preparation were considered: 1) ex-situ sintering of a printed stand-alone cathode layer and 2) infiltration of cathode materials on a cathode scaffold. For the first type, La0.58Sr0.4Co0.2Fe0.8O3−δ mixed with Gadolinium Doped Ceria (LSFC-GDC) was used as cathode materials. For the second type, Samarium Barium Strontium Cobalt oxide (SBSCo) was infiltrated in the cathode scaffold. Cell performance was evaluated through IV curve, power density, and electrochemical impedance spectroscopy. The cell with printed stand-alone cathode showed very poor performance in terms of Maximum Power Density (MPD) (less than 5 mW/cm2), associated with very high polarization resistance. In comparison with printed stand-alone cathode structure, the cell with the cathode scaffold showed much better performance in terms of Maximum Power Density (MPD) (140 mW/cm2) , but more tuning is still required to make it comparable to state-of-the-art SOFC

Micromobility: Progress, benefits, challenges, policy and regulations, energy sources and storage, and its role in achieving sustainable development goals

Micromobility is dominant in urban areas, enhancing the transportation sustainability and assisting in fulfilling the United Nations Sustainable Development Goals (SDGs). This work provides an overall assessment of micromobility: its role under SDGs, policy options, micromobility regulations, emerging technologies, utilisation determinants, energy source, and energy storage. The analysis shows that micromobility could play a major role in achieving the SDGs, specifically SDG 3 (Good Health and Well-being) by lowering toxic gas emissions and reducing projected traffic accidents. Also, the effect on SDG 8 (Decent Work and Economic Growth) by reducing the transportation footprint, on SDG 11 (Sustainable Cities and Communities) by increasing transposition accessibility, reducing traffic congestion and improving the air quality, and equally on SDG 12 (Responsible Consumption and Production) by reducing transportation footprint and increase the sources efficiency. Moreover, micromobility affects SDG 13 (Climate Action) by reducing the greenhouse gases. Furthermore, the analysis shows a clear gap in literature and publications on micromobility, especially in energy management and energy storage area. This review shows that new technology of renewable energy and energy storage could play a significant role in achieving the sustainability of micromobility therefore achieving the SDGs

Polymer nanoparticles and nanofibers: Drug delivery and environmental applications

Since \u201cnanotechnology\u201d was presented by Nobel laureate Richard P. Feynman during his well famous 1959 lecture \u201cThere\u2019s Plenty of Room at the Bottom\u201d, there have been made various revolutionary developments in the field of nanotechnology. However, nanotechnology has emerged in the last decade as an exciting new research field. Nanotechnology represents the design, production, and application of materials at atomic, molecular and macromolecular scales, in order to produce new nanosized structures where at least one dimension is of roughly 1 to 100 nm, i.e., less than 0.1 \u3bcm. However, materials below or next to 1 \u3bcm (1000 nm) can be also commonly referred as nanomaterials or, more correctly, ultrathin materials. According to this, specifically within fiber science related literature, fibers with diameters below 1 \u3bcm are broadly accepted as nanofibers. Nanotechnology and nanoscience studies have emerged rapidly during the past years in a broad range of product domains. Today, nanoscience represents one of the rapidly growing scientific disciplines due to its enormous potential and impact in many different technological and engineering applications, which includes the development of new materials with novel and advanced performances. Recently, the nano-scaled materials have attracted extensive research interests due to their high anisotropy and huge specific surface area. Furthermore, the continuously increasing interest in the nanostructure materials results from their numerous potential applications in various areas, particularly in biomedical sciences. Today, nanofibers and nanoparticles are at the forefront of nanotechnology because of their unique properties such as low density, extremely high surface area to volume ratio, flexibility in surface functionalities, superior mechanical performance (e.g. stiffness and tensile strength), and high pore volume and controllable pore size that cannot be found in other structures. In this context, our researches have been concentrated on the production and modification of polymeric nanofibers and nanoparticles as drug delivery and environment applications. To this purpose, selected materials for the nanofibers development (polyhedral oligomeric silsesquioxanes, modified poly(amido-amine) dendrimers, and modified hyperbranched polyglycerol) were combined with biopolymers, namely (poly(L-lactide) (PLLA) and poly(\u3b5-caprolactone) (PCL) which enable us to overcome typical shortcomings of the above polymer matrices. As well, poly(styrene-co-maleic anhydride) (PSMA) amphiphilic copolymer was used for production of nanoparticles

Charge Transport in Two-Photon Semiconducting Structures for Solar Fuels

Semiconducting heterostructures are emerging as promising light absorbers and offer effective electron–hole separation to drive solar chemistry. This technology relies on semiconductor composites or photoelectrodes that work in the presence of a redox mediator and that create cascade junctions to promote surface catalytic reactions. Rational tuning of their structures and compositions is crucial to fully exploit their functionality. In this review, we describe the possibilities of applying the two-photon concept to the field of solar fuels. A wide range of strategies including the indirect combination of two semiconductors by a redox couple, direct coupling of two semiconductors, multicomponent structures with a conductive mediator, related photoelectrodes, as well as two-photon cells are discussed for light energy harvesting and charge transport. Examples of charge extraction models from the literature are summarized to understand the mechanism of interfacial carrier dynamics and to rationalize experimental observations. We focus on a working principle of the constituent components and linking the photosynthetic activity with the proposed models. This work gives a new perspective on artificial photosynthesis by taking simultaneous advantages of photon absorption and charge transfer, outlining an encouraging roadmap towards solar fuels