Ultralow-Overpotential Acidic Oxygen Evolution Reaction Over Bismuth Telluride-Carbon Nanotube Heterostructure with Organic Framework

The state-of-the-art iridium and ruthenium oxides-based materials are best known for high efficiency and stability in acidic oxygen evolution reaction (OER). However, the development of economically feasible catalysts for water-splitting technologies is challenging by the requirements of low overpotential, high stability, and resistance of catalysts to dissolution during the acidic oxygen evolution reaction . Herein, an organometallic core-shell heterostructure composed of a carbon nanotube core (CNT) and bismuth telluride (Bi2Te3) shell (denoted as nC-Bi2Te3) is designed and use it as a catalyst for the acidic OER. The proposed catalyst achieves an ultralow overpotential of 160 mV at 10 mA cm-2 (geometrical), thereby outperforming most of the state-of-the-art precious-metal-based catalysts. The low Tafel slope of 30 mV dec-1 and charge transfer resistance (RCT) of 1.5 Ω demonstrate its excellent electrocatalytic activity. The morphological and chemical compositions of nC-Bi2Te3 enable the generation of ─OH functional group in the Bi─Te sections formed via a ligand support, which enhances the absorption capacity of H+ ions and increases the intrinsic catalytic activity. The presented insights regarding the material composition-structure relationship can help expand the application scope of high-performance catalysts.

Engineering MoSe2/WS2 Hybrids to Replace the Scarce Platinum Electrode for Hydrogen Evolution Reactions and Dye-Sensitized Solar Cells

In recent times, two-dimensional transition-metal dichalcogenides (TMDs) have become extremely attractive and proficient electrodes for dye-sensitized solar cells (DSSCs) and water electrolysis hydrogen evolution as alternatives to the scarce metal platinum (Pt). The active TMD molybdenum selenide (MoSe₂) and tungsten disulfide (WS₂) are inspiring systems owing to their abundance of active sulfur and selenium sites, but their outputs are lacking due to their inactive basal planes and ineffective transport behavior. In this work, van der Waals interrelated MoSe₂/WS₂ hybrid structures were constructed on conducting glass substrates by chemicophysical methodologies. For the first time, the constructed MoSe₂/WS₂ structures were effectively used as a counter electrode for DSSCs and an active electrode for hydrogen evolution to replace the nonabundant Pt. The assembled DSSCs using the designed MoSe₂/WS₂ heterostructure counter electrode provided a superior power-conversion efficiency of 9.92% and a photocurrent density of 23.10 mA·cm^-2, unmatchable by most of the TMD-based structures. The MoSe₂/WS₂ heterostructure displayed excellent electrocatalytic hydrogen evolution behavior with a 75 mV overpotential to drive a 10 mA·cm^-2 current density, a 60 mV·dec^-1 Tafel slope, and an over 20 h durable process in an acidic medium. The results demonstrated the advantages of the MoSe₂/WS₂ hybrid development for generating interfacial transport and active facet distribution and enriching the electrocatalytic activity for DSSCs and the water-splitting hydrogen evolution process.

An all carbon dye sensitized solar cell: A sustainable and low-cost design for metal free wearable solar cell devices

Lightweight carbon electrodes are the new candidates for photovoltaic devices due to their temperature resistivity, ease of fabrication, and skin comfortability. Herein, a sustainable and facile strategy has been proposed for metal free all carbon dye sensitized solar cell (C-DSSC), assembled by stacking carbon front electrode (CFE) and carbon counter electrode (CCE). The CFE demonstrated adequate light transmittance (70-50%) while maintaining efficient photon absorption and charge separation mechanism due to dye coated TiO₂ nanorods (P25-R). The graphene dip coated carbon counter electrode (Gr@CCE) possesses remarkable electro catalytic activity towards I₃^-/I^- redox couple with low charge transfer resistance (R_CT = 0.79 Ω). The sustainable design of C-DSSC attained ~6 ± 0.5% efficiency with high photocurrent density of 18.835 mA. cm^-2. The superior performance of C-DSSC is accredited to its improved charge mobility, low internal resistance, and better interfacial electrode contact. The thickness of C-DSSC is ≤3 mm eliminates the need for rigid glass in DSSC.

Ultrasonic-assisted deacetylation of cellulose acetate nanofibers: A rapid method to produce cellulose nanofibers

Herein we report a rapid method for deacetylation of cellulose acetate (CA) nanofibers in order to produce cellulose nanofibers using ultrasonic energy. The CA nanofibers were fabricated via electrospinning thereby treated with NaOH and NaOH/EtOH solutions at various pH levels for 30, 60 and 90min assisted by ultrasonic energy. The nanofiber webs were optimized by degree of deacetylation (DD%) and wicking behavior. The resultant nanofibers were further characterized by FTIR, SEM, WAXD, DSC analysis. The DD% and FTIR results confirmed a complete conversion of CA nanofibers to cellulose nanofibers within 1h with substantial increase of wicking height. Nanofibers morphology under SEM showed slightly swelling and no damage of nanofibers observed by use of ultrasonic energy. The results of ultrasonic-assisted deacetylation are comparable with the conventional deacetylation. Our rapid method offers substantially reduced deacetylation time from 30h to just 1h, thanks to the ultrasonic energy.

A PVdF-based electrolyte membrane for a carbon counter electrode in dye-sensitized solar cells

This research demonstrates the design and operation of a dye-sensitized solar cell (DSSC) with a multi-walled carbon nanotube counter electrode (CE) and a pore-filled membrane consisting of polyvinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP) as an electrolyte.

Highly Functional TNTs with Superb Photocatalytic, Optical, and Electronic Performance Achieving Record PV Efficiency of 10.1% for 1D-Based DSSCs

Different nanostructures of TiO2 play an important role in the photocatalytic and photoelectronic applications. TiO2 nanotubes (TNTs) have received increasing attention for these applications due to their unique physicochemical properties. Focusing on highly functional TNTs (HF-TNTs) for photocatalytic and photoelectronic applications, this study describes the facile hydrothermal synthesis of HF-TNTs by using commercial and cheaper materials for cost-effective manufacturing. To prove the functionality and applicability, these TNTs are used as scattering structure in dye-sensitized solar cells (DSSCs). Photocatalytic, optical, Brunauer-Emmett-Teller (BET), electrochemical impedance spectrum, incident-photon-to-current efficiency, and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy characterizations are proving the functionality of HF-TNTs for DSSCs. HF-TNTs show 50% higher photocatalytic degradation rate and also 68% higher dye loading ability than conventional TNTs (C-TNTs). The DSSCs having HF-TNT and its composite-based multifunctional overlayer show effective light absorption, outstanding light scattering, lower interfacial resistance, longer electron lifetime, rapid electron transfer, and improved diffusion length, and consequently, J SC , quantum efficiency, and record photoconversion efficiency of 10.1% using commercial N-719 dye is achieved, for 1D-based DSSCs. These new and highly functional TNTs will be a concrete fundamental background toward the development of more functional applications in fuel cells, dye-sensitized solar cells, Li-ion batteries, photocatalysis process, ion-exchange/adsorption process, and photoelectrochemical devices.

Fabrication of a flexible and conductive lyocell fabric decorated with graphene nanosheets as a stable electrode material

Textile electrodes are highly desirable for wearable electronics as they offer light-weight, flexibility, cost effectiveness and ease of fabrication. Here, we propose the use of lyocell fabric as a flexible textile electrode because of its inherently super hydrophilic characteristics and increased moisture uptake. A highly concentrated colloidal solution of graphene oxide nanosheets (GONs) was coated on to lyocell fabric and was then reduced in to graphene nanosheets (GNs) using facile chemical reduction method. The proposed textile electrode has a very high surface conductivity with a very low value of surface resistance of only 40Ωsq(-1), importantly without use of any binding or adhesive material in the processing step. Atomic force spectroscopy (AFM) and Transmission electron microscopy (TEM) were conducted to study the topographical properties and sheet exfoliation of prepared GONs. The surface morphology, structural characterization and thermal stability of the fabricated textile electrode were studied by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X ray photon spectroscopy (XPS), Raman spectroscopy, Wide angle X ray diffraction spectroscopy (WAXD) and Thermogravimetric analysis (TGA) respectively. These results suggest that the GONs is effectively adhered on to the lyocell fabric and the conversion of GONs in to GNs by chemical reduction has no adverse effect on the crystalline structure of textile substrate. The prepared graphene coated conductive lyocell fabric was found stable in water and electrolyte solution and it maintained nearly same surface electrical conductivity at various bending angles. The electrical resistance results suggest that this lyocell based textile electrode (L-GNs) is a promising candidate for flexible and wearable electronics and energy harvesting devices.

A Novel Activated-Charcoal-Doped Multiwalled Carbon Nanotube Hybrid for Quasi-Solid-State Dye-Sensitized Solar Cell Outperforming Pt Electrode

Highly conductive mesoporous carbon structures based on multiwalled carbon nanotubes (MWCNTs) and activated charcoal (AC) were synthesized by an enzymatic dispersion method. The synthesized carbon configuration consists of synchronized structures of highly conductive MWCNT and porous activated charcoal morphology. The proposed carbon structure was used as counter electrode (CE) for quasi-solid-state dye-sensitized solar cells (DSSCs). The AC-doped MWCNT hybrid showed much enhanced electrocatalytic activity (ECA) toward polymer gel electrolyte and revealed a charge transfer resistance (RCT) of 0.60 Ω, demonstrating a fast electron transport mechanism. The exceptional electrocatalytic activity and high conductivity of the AC-doped MWCNT hybrid CE are associated with its synchronized features of high surface area and electronic conductivity, which produces higher interfacial reaction with the quasi-solid electrolyte. Morphological studies confirm the forms of amorphous and conductive 3D carbon structure with high density of CNT colloid. The excessive oxygen surface groups and defect-rich structure can entrap an excessive volume of quasi-solid electrolyte and locate multiple sites for iodide/triiodide catalytic reaction. The resultant D719 DSSC composed of this novel hybrid CE fabricated with polymer gel electrolyte demonstrated an efficiency of 10.05% with a high fill factor (83%), outperforming the Pt electrode. Such facile synthesis of CE together with low cost and sustainability supports the proposed DSSCs' structure to stand out as an efficient next-generation photovoltaic device.

Multiwalled carbon nanotube coated polyester fabric as textile based flexible counter electrode for dye sensitized solar cell

Textile wearable electronics offers the combined advantages of both electronics and textile characteristics.

Prevalence, awareness and determinants of contraceptive use in Qatari women

We determined the knowledge of, attitude to and practice of contraception and the associated sociodemographic factors among a representative sample 1130 Qatari married women aged 18-49 years. Data were collected by questionnaire. The mean age of the women was 32.5 (SD 7.6) years. The vast majority (94.6%) knew about contraception but of these 1070, only 694 (64.9%) were in favour of contraception. Knowledge of contraception increased with increasing level of education (P < 0.001), but decreased the lower the household income (P = 0.002). Only 511 (47.8%) women were currently using contraceptives, which was significantly associated with age, husband's age, years of marriage, education level, income level and attitude to family planning. The most commonly known and used contraceptives were intrauterine device and pills. Friends were the most common source of knowledge about family planning method (80.0%).

Expanded services for intrauterine contraception in Sudan

Twenty nurse-midwives in government service in the Sudan (health visitors) were trained to provide intrauterine contraceptives in a research project designed to evaluate the safety of insertion of IUDs by medical personnel who are not physicians. After training, they inserted 763 IUDs. Independent evaluation of 520 clients was conducted by obstetrician-gynecologists who found that only six (1.2%) had been incorrectly inserted. Outcomes for clients of the health visitors with respect to perforations, infections, expulsions, and pregnancies compared well with those of eight physicians who participated in the study. The research strongly supports the concept of nurse-midwife training for IUD insertions which would greatly expand the availability of family planning services and would conserve physician time and skills for problem cases.