Review of Progress and Prospects in Research on Enzymatic and Non- Enzymatic Biofuel Cells; Specific Emphasis on 2D Nanomaterials

Energy generation from renewable sources and effective management are two critical challenges for sustainable development. Biofuel Cells (BFCs) provide an elegant solution by combining these two tasks. BFCs are defined by the catalyst used in the fuel cell and can directly generate electricity from biological substances. Various nontoxic chemical fuels, such as glucose, lactate, urate, alcohol, amines, starch, and fructose, can be used in BFCs and have specific components to oxide fuels. Widely available fuel sources and moderate operational conditions make them promise in renewable energy generation, remote device power sources, etc. Enzymatic biofuel cells (EBFCs) use enzymes as a catalyst to oxidize the fuel rather than precious metals. The shortcoming of the EBFCs system leads to integrated miniaturization issues, lower power density, poor operational stability, lower voltage output, lower energy density, inadequate durability, instability in the long-term application, and incomplete fuel oxidation. This necessitates the development of non-enzymatic biofuel cells (NEBFCs). The review paper extensively studies NEBFCs and its various synthetic strategies and catalytic characteristics. This paper reviews the use of nanocomposites as biocatalysts in biofuel cells and the principle of biofuel cells as well as their construction elements. This review briefly presents recent technologies developed to improve the biocatalytic properties, biocompatibility, biodegradability, implantability, and mechanical flexibility of BFCs.This work was supported by the Qatar National Research Fund (a member of Qatar Foundation) under UREP grant #UREP28-052-2-020. The statements made herein are solely the responsibility of the authors

Designing super-fast trimodal sponges using recycled polypropylene for organics cleanup

Abstract Sorbent pads and films have been commonly used for environmental remediation purposes, but designing their internal structure to optimize access to the entire volume while ensuring cost-effectiveness, ease of fabrication, sufficient strength, and reusability remains challenging. Herein, we report a trimodal sorbent film from recycled polypropylene (PP) with micropores, macro-voids, and sponge-like 3D cavities, developed through selective dissolution, thermally induced phase separation, and annealing. The sorbent has hundreds of cavities per cm2 that are capable of swelling up to twenty-five times its thickness, allowing for super-fast saturation kinetics (within 30 s) and maximum oil sorption (97 g/g). The sorption mechanism follows a pseudo-second-order kinetic model. Moreover, the sorbent is easily compressible, and its structure is retained during oil sorption, desorption, and resorption, resulting in 96.5% reuse efficiency. The oil recovery process involves manually squeezing the film, making the cleanup process efficient with no chemical treatment required. The sorbent film possesses high porosity for effective sorption with sufficient tensile strength for practical applications. Our integrated technique results in a strengthened porous polymeric structure that can be tailored according to end-use applications. This study provides a sustainable solution for waste management that offers versatility in its functionality

Up-cycling plastic waste into swellable super-sorbents

Environmental pollution caused by plastic waste and oil spills has emerged as a major concern in recent years. Consequently, there has been a growing interest in exploring innovative solutions to address these challenges. Herein, we report a method to upcycle polyolefins-based plastic waste by converting it into a bimodal super-oleophilic sorbent using dissolution, spin-coating, and annealing techniques. The resulting sorbent possesses an extensive network of pores and cavities with a size range from 0.5 to 5 µm and 150–200 µm, respectively, with an average of 600 cavities per cm2. Each cavity can swell up to twenty times the thickness of the sorbent, exhibiting sponge-like behavior. The sorbent had an oil uptake capacity of 70–140 g/g, depending on the type of sorbate and dripping time. Moreover, the sorbent can be mechanically or manually squeezed to recover the sorbed oil. Our integrated methodology provides a promising approach to upcycling plastic waste as an abundant source of value-added materials.This publication was made possible by NPRP grant number NPRP12S-0325-190443 from the Qatar National Research Fund (a member of the Qatar Foundation). Open Access funding provided by Qatar National Library. The authors would also like to acknowledge Core Labs, Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Qatar, for providing assistance in SEM and XPS.Scopu

Reduced graphene aerogels as energy efficient selective oil sorbents

Graphene aerogels are widely used in the oil–water system as they possess high internal surface area and super-oleophilic properties. However, they tend to absorb water along with oil, and to overcome this problem; surface coatings are generally employed using expensive fluoro-silane compounds. It leads to an increase in production costs and environmental concerns. Herein, we report super-hydrophobic 3D graphene aerogels as selective oil sorbent for oil–water​ separation. The reduction of oxygen-containing functional groups on the surface of graphene aerogels has been studied and characterized with FTIR. The thermal treatment of up to 700 °C was carried out using an in-house flow system. The gases used to reduce graphene oxide aerogel are H2and N2with an optimized ratio of 5:95. The presence of H2significantly decreased the oxygen-containing functional groups in graphene aerogel. The increase in the C/O ratio results in higher uptake capacity due to higher surface area and pore volume. The thermal reduction yields a C/O ratio of 24:1, slightly higher than most reported values

Free-standing polypropylene porous thin films using energy efficient coating technique

Amongst various techniques to prepare thin films, spin coating takes less time to make thin films, is less energy-intensive, is easier to use, and provides reproducible results quickly. It is observed that such a user-friendly and quick process has hardly been explored to prepare polyolefin-based free-standing porous or nonporous thin films. Herein, we report a free-standing thin film of at least 5μm made from polypropylene using the spin coating technique. Our methodology utilizes lower embodied energy and generates lower carbon footprints than the conventional melt extrusion technique. The thin films prepared from the spin coating technique was investigated with DSC, XRD, SEM, XPS, etc., which suggested the heated thin films showed more crystallinity and strength compared to unheated thin films. The SEM images revealed a fibrous structure with a pore size range from 1-10μm. The tensile strength and modulus of the as-prepared thin films were found to be 7 MPa and 583 MPa, respectively. Also, enthalpy change of 84 J/g and relative crystallinity of 41% were obtained. The as-prepared thin film can be used in various applications with minor modifications, such as in coating layers on the solid surface, porous sorbent, and filtration membrane.This publication was made possible by NPRP grant number NPRP12S-0325-190443 from the Qatar National Research Fund (a member of the Qatar Foundation)

Free-standing polypropylene porous thin films using energy efficient coating technique

Amongst various techniques to prepare thin films, spin coating takes less time to make thin films, is less energy-intensive, is easier to use, and provides reproducible results quickly. It is observed that such a user-friendly and quick process has hardly been explored to prepare polyolefin-based free-standing porous or nonporous thin films. Herein, we report a free-standing thin film of at least 5μmmade from polypropylene using the spin coating technique. Our methodology utilizes lower embodied energy and generates lower carbon footprints than the conventional melt extrusion technique. The thin films prepared from the spin coating technique was investigated with DSC, XRD, SEM, XPS, etc., which suggested the heated thin films showed more crystallinity and strength compared to unheated thin films. The SEM images revealed a fibrous structure with a pore size range from 1-10μm. The tensile strength and modulus of the as-prepared thin films were found to be 7 MPa and 583 MPa, respectively. Also, enthalpy change of 84 J/g and relative crystallinity of 41% were obtained. The as-prepared thin film can be used in various applications with minor modifications, such as in coating layers on the solid surface, porous sorbent, and filtration membrane

A facile energy-efficient approach to prepare super oil-sorbent thin films

Oil spills on water surface and shoreline have caused significant water pollution, and one of the ways to deal with them is to use oil sorbents. An effective sorbent provides high oil uptake and retention values, high selectivity, super-fast uptake kinetics, and sufficient mechanical strength to ensure practical application under different conditions. In this regard, synthetic sorbents made up of graphene, carbon nanotubes, and polymers in the form of aerogels, thin films, pads, and non-woven fibers have been widely explored. However, none of them addresses all the attributes of an ideal oil sorbent. Aerogels provide extremely high uptake values, but they are so light that it is difficult for the end user to handle them. On the other hand, thin films and non-woven fibers can quickly absorb oil but suffer from low uptake capacity with low retention values. Similarly, commercial oil sorbent pads have sufficient mechanical strength, but low uptake capacity compared to aerogels. Herein, we present a super oil sorbent with a porous structure using a facile energy-efficient approach. The as-prepared sorbent comprises a porous thin film with micropores and macro-cavities, resulting in super-fast uptake kinetics and a high oil uptake value of 85 g/g. Moreover, tensile test results confirm sorbent’s effectiveness in spill response. Lastly, our unique design does not involve expensive hydrophobic functionalization and thus utilizes lower embodied energy and generates lower carbon footprints