Nanotechnology is utilized well in the development and improvement of the performance in Solid Oxide Fuel Cells (SOFCs). The high operating temperature of SOFCs (700–900°C) has resulted in serious ...demerits regarding their overall performance and durability. Therefore, the operating temperature has been reduced to an intermediate temperature range of approximately 400–700°C which improved performance and, subsequently, commercialized SOFCs as portable power sources. However, at reduced temperature, challenges such as an increase in internal resistance of the fuel cell components arise. Although, this may not be as serious as problems encountered at high temperature, it still significantly affects the performance of SOFCs. This review paper addresses the work of researchers in the application of nanotechnology in fabricating SOFCs through distinct methods. These methods have successfully omitted or at least reduced the internal resistance and showed considerable improvement in power density of the SOFCs at reduced temperatures.
The aims of this review article is to understand the mechanism of proton-conducting solid oxide fuel cells (SOFCs) and compare it with conventional SOFC, to understand how dopants help to improve the ...conductivity and stability of doped materials, to investigate and analyze the effect or impact (in terms of conductivity and stability) of different types of dopants on the materials as proton-conducting electrolyte in intermediate temperature solid oxide fuel cell (IT-SOFC) and to study the experimental reviews on the methods in synthesizing the materials. Emphasis is given on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. This review will be focusing more on BaCeO3 and BaZrO3 as these electrolyte materials were in the focus of research during the past decades due to their considerable proton conductivity and stability.
Hydrogen clean energy carrier as one of most essential clean and sustainable resource with main applications in both research and industry diverse.
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•H2 exists mostly in plant ...materials and is not readily available in nature.•H2 fuel is nonmetallic, non-toxic and can show higher energy compared to other fuels.•H2 industry key challenges are clarified to facilitate H2 usage as alternative energy.
The energy demand worldwide has increased significantly with the increase in population. This is because energy is needed in almost every activity. For example, in industry, working, cleaning, transportation and commuting from one place to another. The majority of energy being used is obtained from fossil fuels, which are not renewable resources and require a longer time to recharge or return to its original capacity. Energy from fossil fuels is cheaper but it faces some challenges compared to renewable energy resources. Thus, one of the most potential candidates to fulfill the energy requirements are renewable resources and the most environmentally friendly fuel is hydrogen (H2). Hydrogen exists mostly in plant materials and is not readily available in nature. It is necessary to produce hydrogen from available feedstock (water), which covers 70% of the earth. Moreover, hydrogen under standard pressure and temperature has an important merit; it can be obtained from renewable resources. Although, currently it is produced from fossil fuels. Hydrogen as a fuel is nonmetallic, non-toxic and can generate higher energy than gasoline on a mass basis. However, to employ hydrogen as a fuel, extensive research is essential to investigate and design on-board applications. Also, the cost of producing hydrogen (renewable) is expensive compared to gasoline (fossil). Thus, the production of H2 from renewable resources and from fossil fuels requires tremendous effort. One of these efforts is to generate H2 from biofuels as it is considered a promising technique that can help manage hydrogen from food waste. In addition, hydrogen storage materials are still lacking in both volumetric and gravimetric density. In this review, the key challenges that hydrogen industry are confronting are introduced and highlighted to facilitate the use of hydrogen as an alternative energy.
CSZM compounds were synthesized by dry chemistry route with 5, 10, and 15% dopant of Mg dopants in the Ce 0.8−2x Sm 0.2 Zrx Mgx O2−d, {x = 0.05, 0.1 & 0.15}. The newly investigated materials were ...physically, chemically, and electrochemically studied and have shown promising results. The CSZM was crystalized in a fluorite structure with a pure cubic phase in a space group Fm3m and cell parameter a = 5.401742 °A and theoretical density from 7.6 to 8.9 after firing in the air with a final temperature of 1400 °C. Characterization of the structure and indexing of electrolyte materials were made after X-ray diffraction (XRD) testing. A Scanning electron microscope (SEM) morphological analysis was used to examine the microstructure details. Electrochemical impedance spectroscopy (EIS) measurements were performed from 400 °C to 700 °C which show the highest conductivity value of 1.0461 × 10+1 S/cm at 700 °C. In comparison, the minimum value was 2.7329 × 10−2 S/cm at 400 °C, and the total activation energy (Ea°A) was found to be 0.6865 eV under 5% H2/Ar.
In this paper, we contribute to the results of Bakhet et al. (Integral Transforms Spec. Funct. 30:138–156,
2019
) by applying fractional operators to the Wright hypergeometric matrix functions. We ...give matrix recurrence relations and integral formulas for the Wright hypergeometric matrix functions. We also clarify particular cases of the main results.
Nanostructured materials have gained much attention in recent engineering and material- science research due to their unique structural makeup, which stands them out from their bulk counterparts. ...Their novel properties of tiny-size structural elements (molecules or crystallites, clusters) of nanoscale dimensions (1 to 100 nm) make them a perfect material for energy applications. The recent keen interest in nanostructured materials research by academia and industrial experts arises from the unique variable characteristics of increased electrical and thermal conductivity. This occurs as nanostructured materials undergo a transient process from infinite-extended solid to a particle of ascertainable numbers of atoms. The commercial and energy sectors are very interested in developing and expanding simple synthetic pathways for nanostructured-electrocatalysts materials to aid in optimizing the number of active regions. Over the decades, various techniques have been put forward to design and synthesize nanostructured-electrocatalysts materials for electrochemical generation of energy and storage applications. As a result, the design of fuel cells, supercapacitors, and energy-storage devices has advanced significantly. This review provides a comprehensive outlook of various synthesis techniques and highlight the challenges of nanostructured- electrocatalysts materials application in fuel cells. Several synthesis methods are discussed and summarized for enhanced nanomaterial preparation and high product attainment with the sol-gel synthesis method being emphasized. The design methodology for an effective nanostructured electrocatalysts with high efficiency for fuel cells was also discussed.
The BaCe0.7Zr0.1Y0.2−xZnxO3−δ (x = 0.05, 0.10, 0.15, 0.20) has been synthesized by the conventional solid state reaction method for application in protonic solid oxide fuel cell. The phase purity and ...lattice parameters of the materials have been studied by the room temperature X-ray diffraction (XRD). Scanning electron microscopy (SEM) has been done for check the morphology and grain growth of the samples. The chemical and mechanical stabilities have been done using thermogravimetric analysis (TGA) in pure CO2 environment and thermomechanical analysis (TMA) in Argon atmosphere. The XRD of the materials show the orthorhombic crystal symmetry with Pbnm space group. The SEM images of the pellets show that the samples sintered at 1200 °C are highly dense. The XRD after TGA in CO2 and thermal expansion measurements confirm the stability. The particles of the samples are in micrometer ranges and increasing Zn content decreases the size. The conductivity measurements have been done in 5% H2 with Ar in dry and wet atmospheres. All the materials show high proton conductivity in the intermediate temperature range (400–700 °C). The maximum proton conductivity was found to be 1.0 × 10−2 S cm−1 at 700 °C in wet atmosphere for x = 0.10. From our study, 10 wt % of Zn seems to be optimum at the B-site of the perovskite structure. All the properties studied here suggest it can be a promising candidate of electrolyte for IT-SOFCs.
Rietveld analysis confirms that BaCe0.7Zr0.1Y0.2−xZnxO3−δ (x = 0.05, 0.10, 0.15, 0.20) crystallized in the orthorhombic symmetry after sintering at 1200 °C which are highly dense and good protonic conductors. Insert shows the schematic 3D diagram (left) and high density SEM profile (right). Display omitted
•The materials were in single phase orthorhombic structure at 1200 °C.•Highly dense at 1200 °C and large SEM morphology for IT-SOFC electrolyte.•High chemical stability up to 1000 °C under carbon dioxide.•It shows high conductivity of 1.0 × 10−2 S cm−1 at 700 °C in wet H2.
The coronavirus disease 2019 (COVID-19) pandemic has impacted all aspects of our lives, including education and the economy, as we know it. Governments have issued stay-at-home directives, and as a ...result, colleges and universities have been shut down across the world. Hence, online classes have become a key component in the continuity of education. The present study aimed to analyze the impact of the COVID-19 pandemic on online education at the College of Medicine (COM) of Alfaisal University in Riyadh, Saudi Arabia. Between March and April 2020, we emailed a survey to 1,289 students and faculty members of the COM. We obtained 208 responses (16.1%); 54.8% of the respondents were females, and 66.8% were medical students; 14.9% were master’s students, and 18.3% were faculty. Among the respondents, 41.8% reported having little or no online teaching/learning experience before the pandemic, and 62.5% preferred blending online and face-to-face instruction. The reported challenges to online medical education during the COVID-19 pandemic included issues related to communication (59%), student assessment (57.5%), use of technology tools (56.5%), online experience (55%), pandemic-related anxiety or stress (48%), time management (35%), and technophobia (17%). Despite these challenges, most of the respondents (70.7%) believed that the COVID-19 pandemic has boosted their confidence in the effectiveness of online medical education. Consequently, 76% of participants intended to integrate the online expertise garnered during the pandemic into their practice. In short, the modern study demonstrated a largely positive impact of the COVID-19 pandemic on online medical education.
The coronavirus disease 2019 (COVID-19) pandemic and the policies to contain it have been a near ubiquitous exposure in the US with unknown effects on depression symptoms.
To estimate the prevalence ...of and risk factors associated with depression symptoms among US adults during vs before the COVID-19 pandemic.
This nationally representative survey study used 2 population-based surveys of US adults aged 18 or older. During COVID-19, estimates were derived from the COVID-19 and Life Stressors Impact on Mental Health and Well-being study, conducted from March 31, 2020, to April 13, 2020. Before COVID-19 estimates were derived from the National Health and Nutrition Examination Survey, conducted from 2017 to 2018. Data were analyzed from April 15 to 20, 2020.
The COVID-19 pandemic and outcomes associated with the measures to mitigate it.
Depression symptoms, defined using the Patient Health Questionnaire-9 cutoff of 10 or higher. Categories of depression symptoms were defined as none (score, 0-4), mild (score, 5-9), moderate (score, 10-14), moderately severe (score, 15-19), and severe (score, ≥20).
A total of 1470 participants completed the COVID-19 and Life Stressors Impact on Mental Health and Well-being survey (completion rate, 64.3%), and after removing those with missing data, the final during-COVID-19 sample included 1441 participants (619 participants 43.0% aged 18-39 years; 723 50.2% men; 933 64.7% non-Hispanic White). The pre-COVID-19 sample included 5065 participants (1704 participants 37.8% aged 18-39 years; 2588 51.4% women; 1790 62.9% non-Hispanic White). Depression symptom prevalence was higher in every category during COVID-19 compared with before (mild: 24.6% 95% CI, 21.8%-27.7% vs 16.2% 95% CI, 15.1%-17.4%; moderate: 14.8% 95% CI, 12.6%-17.4% vs 5.7% 95% CI, 4.8%-6.9%; moderately severe: 7.9% 95% CI, 6.3%-9.8% vs 2.1% 95% CI, 1.6%-2.8%; severe: 5.1% 95% CI, 3.8%-6.9% vs 0.7% 95% CI, 0.5%-0.9%). Higher risk of depression symptoms during COVID-19 was associated with having lower income (odds ratio, 2.37 95% CI, 1.26-4.43), having less than $5000 in savings (odds ratio, 1.52 95% CI, 1.02-2.26), and exposure to more stressors (odds ratio, 3.05 95% CI, 1.95-4.77).
These findings suggest that prevalence of depression symptoms in the US was more than 3-fold higher during COVID-19 compared with before the COVID-19 pandemic. Individuals with lower social resources, lower economic resources, and greater exposure to stressors (eg, job loss) reported a greater burden of depression symptoms. Post-COVID-19 plans should account for the probable increase in mental illness to come, particularly among at-risk populations.
•The impact of grazing on SOC is climate-dependent.•Grazing increases SOC for C4 but decreases it for C3 and C3-C4 mixed grasslands.•Grazing increases TN and BD but has no effect on soil pH.
...Livestock grazing intensity (GI) is thought to have a major impact on soil organic carbon (SOC) storage and soil quality indicators in grassland agroecosystems. To critically investigate this, we conducted a global review and meta-analysis of 83 studies of extensive grazing, covering 164 sites across different countries and climatic zones. Unlike previous published reviews we normalized the SOC and total nitrogen (TN) data to a 30cm depth to be compatible with IPCC guidelines. We also calculated a normalized GI and divided the data into four main groups depending on the regional climate (dry warm, DW; dry cool, DC; moist warm, MW; moist cool, MC). Our results show that taken across all climatic zones and GIs, grazing (below the carrying capacity of the systems) results in a decrease in SOC storage, although its impact on SOC is climate-dependent. When assessed for different regional climates, all GI levels increased SOC stocks under the MW climate (+7.6%) whilst there were reductions under the MC climate (−19%). Under the DW and DC climates, only the low (+5.8%) and low to medium (+16.1%) grazing intensities, respectively, were associated with increased SOC stocks. High GI significantly increased SOC for C4-dominated grassland compared to C3-dominated grassland and C3-C4 mixed grasslands. It was also associated with significant increases in TN and bulk density but had no effect on soil pH. To protect grassland soils from degradation, we recommend that GI and management practices should be optimized according to climate region and grassland type (C3, C4 or C3-C4 mixed).
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