Electrospun SnO2-CuO semiconductor composite nanofibers and its electrochemical properties

Composite metal oxide had attracted attention across numerous fields of application due to their synergic combination of properties from their single constituents. Further modification of composite metal oxide into nanostructure, especially 1-dimensional structure was proven to further improve active surface area, carrier transport properties, etc. In this study, a n-type p-type SnO2-CuO composite nanofibers was synthesized through multi-needle electrospinning techniques. The FESEM confirmed the 1-dimensional nanostructures with diameter>100nm whereas XRD showed the coexistence of both SnO2 and CuO crystallite phases within the SnO2-CuO composite. The electrochemical properties of the synthesized samples were subsequently analyzed, concluding that SnO2-CuO composite improved the voltage range of SnO2 as well as the conductivity of the CuO nanofibers. However, from the perspective of the overall performance, the advantages of SnO2 was balanced out by the deficient of CuO, with specific capacity of 249.1F/g for SnO2-CuO, greater than CuO (104.4F/g) but lower than SnO2 (350.4F/g). Altering the ratio of Sn:Cu would be favorable to further improve the performance of the SnO2-CuO material system

Metal oxide nanofibers in solar cells

The motivation to improve the performance of sensitized photovoltaic (PV) cells by enhancing both the surface area and carrier diffusion properties of its photoanode had drawn attention toward utilizing metal oxide nanofibers (NFs). Owing to the anisotropic carrier transport characteristic, NFs had surpassed the nanoparticles analog in achieving higher photoconversion efficiency (PCE) in sensitized PV while preserving the benefit of high surface area. However, the higher density of delocalized trap states in nanostructured materials, compared to the bulk materials, hampered further improvement in the PCE of NF-based sensitized PV cells. This chapter offers a brief explanation of the photoconversion mechanism of sensitized PV cells, followed by a discussion of the importance of utilizing metal oxide NFs as the charge extractor for this specific application. Details on the formation of delocalized trap states and how it impairs the carrier diffusion coefficient are provided. Some techniques for eradicating the effect brought about by the delocalized trap states are offered and reviewed, and challenges for future development of metal oxide NF-based sensitized PV cells are discussed

Ten major challenges for sustainable lithium-ion batteries

Lithium-ion batteries offer a contemporary solution to curb greenhouse gas emissions and combat the climate crisis driven by gasoline usage. Consequently, rigorous research is currently underway to improve the performance and sustainability of current lithium-ion batteries or to develop newer battery chemistry. However, as an industrial product, batteries follow a linear route of waste-intensive production, use, and disposal; therefore, greater circularity would elevate them as sustainable energizers. This article outlines principles of sustainability and circularity of secondary batteries considering the life cycle of lithium-ion batteries as well as material recovery, component reuse, recycling efficiency, environmental impact, and economic viability. By addressing the issues outlined in these principles through cutting-edge research and development, it is anticipated that battery sustainability, safety, and efficiency can be improved, thereby enabling stable grid-scale operations for stationary storage and efficient, safe operation of electric vehicles, including end-of-life management and second-life applications

Pfibrolizer: A new paradigm for large scale electrospinning from lessons learnt from Malaysian kitchen

Electrospinning is a fiber production method, in which a liquid droplet is electrified to generate a jet, followed by stretching and elongation to generate fibers. Electrospinning setup mainly consists of 3 parts, a spinneret, high voltage source and a collector. The currently available electrospinning spinneret in markets has several drawbacks which limits its efficiency. Inspired from the Malaysian kitchen, we have designed a simple electrospinning spinneret head which is beneficial for large scale nanofiber production. This design also allows the user to easily modify the spinneret according to the requirements of morphology and number of fibers

Improving Fresh and End-Used Carbon Surface by Sunlight A Step Forward in Sustainable Carbon Processing

Carbon is at the forefront of sustainable materials; the modification of its surface is pivotal to many traditional and advanced applications. Conventional high-temperature activation or chemical etching for carbon surface modification is time- and energy-intensive as well as requiring a high volume of toxic chemicals; therefore, a cheaper, quicker, and eco-friendly technique is a step forward toward its sustainable processing. Herein, modification of fresh and end-used carbon surface through focusing the sunlight is demonstrated as a clean, sustainable, and instantaneous surface modification technique for electrochemical charge storage application. Temporal evolution of the carbon surface is monitored using field-emission scanning electron microscopy, gas adsorption measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Results demonstrate that solar irradiation led to the rapid release of moisture, which in turn generated newer pores. Electrochemical analyses showed that treating the porous carbon for 20 s boosted its electrical double layer capacitance by 56%. The usefulness of the solar treatment in recovering degraded electrochemical capacitor electrodes was also investigated, where 95% of the electrochemical performance was restored. This work demonstrated the feasibility of utilizing focused sunlight for surface treatment, suggesting utilizing sunlight for a sustainable, activation agent-free, and rapid surface treatment technique

Electrospun ternary composite metal oxide fibers as an anode for lithium-ion batteries

Nickel–cobalt–manganese oxides (NCMs) are widely investigated as cathode materials for lithium-ion batteries (LIBs) given their beneficial synergistic effects of high storability, electrical conductivity, and stability. However, their use as an anode for LIBs has not been adequately addressed. NCM nanofibers prepared using the multi-needle electrospinning technique are examined as the anode in LIBs. The NCM nanofibers demonstrated an initial discharge capacity of ∼1,075 mAh g−1 with an initial capacity loss of ∼42%. Through controlling the conductive additive content, the initial discharge capacity can be further improved to ∼1810 mAh g−1, mostly attributing to the improved interfiber connectivity supported by the significant lowering of impedance when the amount of conductive additive is increased. This study also reveals that the conventional ratio of 80:10:10 wt% (active materials:additives:binder) is not optimal for all samples, especially for the high active surface area electrospun nanofibers

Structural and Electromagnetic Shielding Effectiveness of Carbon-Coated Cobalt Ferrite Nanoparticles Prepared via Hydrothermal Method

The rapid advancement of communication technology has led to an increase in electromagnetic interference (EMI), or electromagnetic (EM) pollution. This is a cause for concern, as EMI can disrupt communication services, damage electronic equipment, and pose health risks. Regulatory bodies are working to develop standards for the safe use of wireless devices, but the problem of EMI is likely to continue to grow as the number of Internet of Thing (IoT) devices continues to increase. To address this issue, this study investigated the effectiveness of carbon-coated cobalt ferrite nanoparticles as a potential material for electromagnetic shielding. The synthesis of cobalt ferrite (CoFe2 O4) nanoparticles was successfully achieved using the co-precipitation method. Subsequently, a carbon coating was applied to the nanoparticles through a hydrothermal process using a 200 mL autoclave made of teflon-lined stainless steel. This process was carried out at a temperature of 180◦ C for a duration of 12 hours, with a heating rate of 8◦ C per minute. This study examined both uncoated and carbon-coated CoFe2 O4 nanoparticles at various ratios of glucose to CoFe2 O4 (1: 1, 2: 1, and 3: 1) using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and higher resolution transmission electron microscopy (HRTEM) analysis. The XRD analysis revealed distinct and well-defined peaks corresponding to CoFe2 O4, indicating the successful synthesis of the nanoparticles. The crystallite size of the uncoated CoFe2 O4 nanoparticles was measured to be 11.47 nm, while for the carbon-coated CoFe2 O4, the average crystallite size was determined to be 14.15 nm through XRD analysis. The results obtained from the FTIR analysis were consistent with previous reports and confirmed the formation of spinel CoFe2 O4 nanoparticles, as suggested by published data. The morphological and structural properties of the prepared samples were further characterized using FESEM and HRTEM analysis, which demonstrated uniformity in both particle size distribution and morphology. Overall, the research findings indicated that the structure and properties of CoFe2 O4 nanoparticles were significantly influenced by the carbon coating process. Notably, the optimum ratio of carbon to CoFe2 O4 was found to be 2: 1, which resulted in the highest carbon thickness. The electromagnetic properties of the samples were evaluated using a vector network analyzer (VNA) and measured S-parameters in the frequency range of 8.2 to 12.4 GHz, known as the x-band region, suitable for radar applications. The sample with a carbon ratio of 2: 1 exhibited the highest total shielding effectiveness (SE) of 17 dB at approximately 10 GHz. As a conclusion, the carbon-coated CoFe2 O4 nanoparticles showed promising potential as an effective material for shielding against electromagnetic wave pollution, particularly when the carbon coating and filler composition reached an optimal point. Additionally, the shielding effectiveness performance of the sample could be further enhanced by incorporating a conductive polymer as an auxiliary material

Electrospinning research and products: The road and the way forward

Electrospinning is one of the most accessed nanofabrication techniques during the last three decades, attributed to its viability for the mass production of continuous nanofibers with superior properties from a variety of polymers and polymeric composites. Large investments from various sectors have pushed the development of electrospinning industrial setups capable of producing nanofibers in millions of kilograms per year for several practical applications. Herein, the lessons learned over three decades of research, innovations, and designs on electrospinning products are discussed in detail. The historical developments, engineering, and future opportunities of electrospun nanofibers (ESNFs) are critically addressed. The laboratory-to-industry transition gaps for electrospinning technology and ESNFs products, the potential of electrospun nanostructured materials for various applications, and academia-industry comparison are comprehensively analyzed. The current challenges and future trends regarding the use of this technology to fabricate promising nano/macro-products are critically demonstrated. We show that future research on electrospinning should focus on theoretical and technological developments to achieve better maneuverability during large-scale fiber formation, redesigning the electrospinning process around decarbonizing the materials processing to align with the sustainability agenda and the integration of electrospinning technology with the tools of intelligent manufacturing and IR 4.0

Quasi-anisotropic benefits in electrospun nickel–cobalt–manganese oxide nano-octahedron as anode for lithium-ion batteries

Despite having a significantly higher capacity (>1000 mA h g−1) as compared to the conventional graphite anode, the adoption of the conversion-type transition metal oxide (TMO) anodes is restricted due to their inferior cycling stability, sluggish ion transport behavior, high potential plateau vs. Li/Li+, etc. Subsequent developments through nanostructuring and chemical composition engineering have improved the electrochemical performance of TMO anodes. Herein, a quasi-anisotropic nano-octahedron quaternary metal oxide composite is designed and synthesized using pilot-scale electrospinning by manipulating the conductivity of the polymeric solution. This morphology is first reported via electrospinning, which routinely produces nanofiber morphology. The fabricated nano-octahedron exhibited slightly higher gravimetry specific capacity (∼1184 mA h g−1 at 100 mA g−1) as compared to the nanofiber counterpart (1075 mA h g−1 at 100 mA g−1), with an initial capacity loss of 37.4% and 38.7%, respectively. Owing to the isotropic volume expansion, the nano-octahedron was capable of retaining 78.9% (or 291.2 mA h g−1) capacity after 500 charge/discharge cycles at 1000 mA g−1, compared to the inferior 24.1% (or 71.1 mA h g−1) for its nanofiber counterpart. Overall, the results discussed here provide valuable information on morphology design for future high-performance TMO anodes

Synthesis and characterization of Al2O3-SnO2 composite nanofibers by electrospinning for dye-sensitized solar cells

Materials engineering has been an inevitable part of technological advancements; many advanced technologies came in effect because of availability of new and high performing materials. This thesis investigates the structural, optical and electrical properties of a novel material, viz. a composite nanofiber containing amorphous Al2O3 and crystalline SnO2; properties of this composite has been benchmarked with pure nanofibers of amorphous Al2O3, crystalline SnO2, and Al-doped SnO2. Rationale of selection of these materials is the fact that Al2O3 is an insulator but offer high specific surface area whereas SnO2 is highly conducting but with compromised surface area – combining high specific surface area and high conductivity in one material would have potential impacts in nanoelectronics. For example, such materials are sought as photoanodes in dye-sensitized solar cells (DSSCs), which generated immense attention in clean energy research due to their capability of operating at dim light intensity. Six materials were prepared containing 5, 10, 25, and 50% of Al2O3 in SnO2 in addition to pure Al2O3 and SnO2 nanofibers by electrospinning technique. The as-spun polymeric fibrous cloths were calcined at 550 oC, which resulted in the crystallite –amorphous composite materials. The prepared samples were studied using Field Emission Scanning Electron Microscope, X-ray Diffraction, X-ray Photoelectron Spectroscopy, UV-Vis Spectrophotometer, Brunauer–Emmett–Teller (BET) surface analysis and Electrochemical Impedance Spectroscopy. Nanofiber structure was confirmed in all the samples. The XRD spectra showed no peak of Al2O3, indicating amorphous Al2O3 whereas SnO2 was fully crystallized. The absorption spectroscopy showed decrease in sample’s absorption and scattering coefficient indicating that higher ratio of Al2O3 in SnO2 is not suitable for the DSSCs application. Energy gap calculated from the absorption spectroscopy resulted in a narrowed energy gap when more Al2O3 was added into SnO2. The BET analysis showed an increase in sample’s surface area with increase in the Al2O3 content in SnO2 and electrochemical impedance spectroscopic analyses showed that the increase in surface area is at the expense of sample’s conductivity. The DSSCs were fabricated using the nanofibers developed here and characterized their photovoltaic properties using current – voltage measurements at AM 1.5 conditions; the cells showed improved performance for the 5-10% of Al2O3 doped in SnO2, with efficiency of 2% compared to SnO2 (~0.5%). Interestingly, the 1:1 SnO2/Al2O3 composite showed a conductivity similar to that of Al2O3; however, this composite when used as a photoanode showed orders of magnitude higher photovoltaic properties compared to that fabricated using pure Al2O3, due to the band bending effect at the nanofibers and cluster interface, facilitating the flow of electrons. This study opens up new opportunities in studying the structure – property correlations in amorphous – crystalline materials composites