Nanostructures in Dye-Sensitized and Perovskite Solar Cells

Due to increase of attention in energy and environmental concerns, there has been much interest developed in clean and renewable energy technologies. The utilization of green and eco-friendly sunlight through solar cells like photovoltaic cells, photo-electrochemical cells, and dye-sensitize and perovskite solar cells (DSSCs and PSCs) produces energy demand. Due to high electron mobility, suitable band alignment, and high optical transparency, the binary and ternary transition metal oxide materials such as TiO2, SnO2, ZnO, WO3, Bi2O3 and SrTiO3, Zn2SnO4, BaSnO3, etc. have attracted considerable attention as DSSC and PSC electrode materials. Highly efficient solar cells with sustainable performance under severe mechanical deformations are in great demand in forming wearable power supply devices, essential for space technologies. In this regard, myriads of studies have progressed in developing the said metal oxides by various means of nanostructure forms. The aim of this chapter is to highlight research background, basic concepts, operating parameters, working principles, theoretical aspects, and selection of materials with essential properties for DSSCs and PSCs applications

Low-cost and biodegradable thermoelectric devices based on van der Waals semiconductors on paper substrates

We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates. The devices are based on thin films of WS2, Te, and BP (P-type semiconductors) and TiS3 and TiS2 (N-type semiconductors), deposited by simply rubbing powder of these materials against paper. The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of (+1.32 ± 0.27) mV/K and (-0.82 ± 0.15) mV/K for WS2 and TiS3, respectively. Additionally, Peltier elements were fabricated by interconnecting the P-type and N-type films with graphite electrodes. A thermopower value up to 6.11 mV/K was obtained when the Peltier element is constructed with three junctions. The findings of this work show proof-of-concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low-cost disposable electronic device

Radially oriented mesoporous TiO2 microspheres with single-crystal–like anatase walls for high-efficiency optoelectronic devices

Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m2/g), a large pore volume (0.164 cm3/g), and highly single-crystal–like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.State Key Basic Research Program of China (2013CB934104 and 2012CB224805), the National Science Foundation (21210004), the Science and Technology Commission of Shanghai Municipality (08DZ2270500), the Shanghai Leading Academic Discipline Project (B108), King Abdulaziz City for Science and Technology (project no. 29-280), and Deanship of Scientific Research, King Saud University–The International Highly Cited Research Group Program (IHCRG#14-102). Y.L. also acknowledges the Interdisciplinary Outstanding Doctoral Research Funding of Fudan University (EZH2203302/001)

Regulating C2H2/CO2 adsorption selectivity by electronic-state manipulation of iron in metal-organic frameworks

Article reports a metal electronic-state manipulation strategy to construct a pair of isostructural and interconvertible Fe-MOFs featuring open Fe centers with different electron densities for efficient C₂H₂/CO₂ separation. The authors show that the presence of Fe[II] centers with a medium-spin-state trail plays a crucial role in the enhanced C₂H₂ selective adsorption

Polymer-Based Electrospun Nanofibers for Biomedical Applications

Electrospinning has been considered a promising and novel procedure to fabricate polymer nanofibers due to its simplicity, cost effectiveness, and high production rate, making this technique highly relevant for both industry and academia. It is used to fabricate non-woven fibers with unique characteristics such as high permeability, stability, porosity, surface area to volume ratio, ease of functionalization, and excellent mechanical performance. Nanofibers can be synthesized and tailored to suit a wide range of applications including energy, biotechnology, healthcare, and environmental engineering. A comprehensive outlook on the recent developments, and the influence of electrospinning on biomedical uses such as wound dressing, drug release, and tissue engineering, has been presented. Concerns regarding the procedural restrictions and research contests are addressed, in addition to providing insights about the future of this fabrication technique in the biomedical field

Polymer-Based Electrospun Nanofibers for Biomedical Applications

Electrospinning has been considered a promising and novel procedure to fabricate polymer nanofibers due to its simplicity, cost effectiveness, and high production rate, making this technique highly relevant for both industry and academia. It is used to fabricate non-woven fibers with unique characteristics such as high permeability, stability, porosity, surface area to volume ratio, ease of functionalization, and excellent mechanical performance. Nanofibers can be synthesized and tailored to suit a wide range of applications including energy, biotechnology, healthcare, and environmental engineering. A comprehensive outlook on the recent developments, and the influence of electrospinning on biomedical uses such as wound dressing, drug release, and tissue engineering, has been presented. Concerns regarding the procedural restrictions and research contests are addressed, in addition to providing insights about the future of this fabrication technique in the biomedical field

Influence of graphene oxide on mechanical, morphological, barrier, and electrical properties of polymer membranes

This paper expresses a short review of research on the effects of graphene oxide (GO) as a nanocomposite element on polymer morphology and resulting property modifications including mechanical, barrier, and electrical conductivity. The effects on mechanical enhancement related to stress measurements in particular are a focus of this review. To first order, varying levels of aggregation of GO in different polymer matrices as a result of their weak inter-particle attractive interactions mainly affect the nanocomposite mechanical properties. The near surface dispersion of GO in polymer/GO nanocomposites can be investigated by studying the surface morphology of these nanocomposites using scanning probe microscopy such as atomic force microscope (AFM) and scanning electron microscope (SEM). In the bulk, GO dispersion can be studied by wide-angle X-ray scattering (WAXD) by analyzing the diffraction peaks corresponding to the undispersed GO fraction in the polymer matrix. In terms of an application, we review how the hydrophilicity of graphene oxide and its hydrogen bonding potential can enhance water flux of these nanocomposite materials in membrane applications. Likewise, the electrical conductivity of polymer films and bulk polymers can be advantageously enhanced via the percolative dispersion of GO nanoparticles, but this typically requires some additional chemical treatment of the GO nanoparticles to transform it to reduced GO. 2015 Production and hosting by Elsevier B.V.The authors acknowledge the support of the ACS-#52997-ND7 Petroleum Research Foundation. The authors extend their sincere appreciations to the Deanship of Scientific Research at King Saud University for its funding this Prolific Research group (PRG-1436-14) for this graphene oxide based membranes review study.Scopu

Nickel oxide carbon nanofiber composite for electrochemical oxidation of methanol

Electrospun fibers of a mixture of polyvinylpyrrolidone (PVP), polyaniline (PANI) and graphene were stabilized for 2 h at 200 °C and then carbonized at 800 °C for 5 h. Composites were prepared by depositing Ni(OH)2 on the carbon nanofibers (CNFs) and calcining them at different temperatures. The composites were characterized using XRD, TEM and SEM. The effect of the calcination temperatures on the electrochemical catalytic properties towards methanol (MeOH) oxidation was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The analysis of the chronoamperometry measurements confirmed a significant increase in the real surface area for the CNF/NiO composite as the calcination temperature increases. The real surface area is increased at calcination temperatures of 400 and 500 oC more than 20 times higher than that calcined at 300 oC. The oxidation of MeOH was not found to be a purely diffusion controlled process. The CNF/NiO composite has shown, not only, a good stability as the potential was cycled between a large potential window, but also, the electrocatalytic properties was enhanced which was attributed to the surface activation during the cyclic process. The impedance parameters were calculated from the EIS measurements proved that this system has two time constants: one for the adsorption and the other for the charge transfer.Scopu

Free-standing and binder-free nickel polymeric nanofiber membrane for electrocatalytic oxidation of ethanol in alkaline solution

In-situ chemical reduction technique was exploited to fabricate free-standing and binder-free active nanocatalyst materials for direct ethanol fuel cells using nickel nanoparticles onto polyvinylidenefluoride-co-hexafluoropropylene membrane [Ni/PVdF-HFP]. Homogeneously distributed nickel nanoparticles with face-centered cubic structure were observed onto smooth membrane surfaces. Cyclic voltammetric measurements indicated the enhanced activity of Ni/PVdF-HFP membrane for oxidizing the alcohol molecules in NaOH solution. The measured oxidation current density increased with increasing the added ethanol concentration into the supporting electrolyte up to 0.64 M. Some kinetic parameters were calculated such as the charge transfer coefficient (α), Tafel slope and exchange current density values to record 0.468, 369 mV dec−1 and 1.28 μA cm−2, respectively. The three dimensional nanostructure of these fabricated metallic membranes and the increased number of their active voids could provide largely exposed surface areas for adsorbed alcohol molecules. The good stability of nickel nanoparticles onto PVdF-HFP membrane surface with minimum leaching level during prolonged ethanol oxidation in alkaline solution can offer unique possibilities for utilizing these polymeric electrocatalyst structures for energy production applications

Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction

A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific capacitances at current densities from 1 to 20 A g-1, with excellent capacitance retention (>90%) at 10 A g-1 for over 10 000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm-2 at 1.65 V vs. the RHE. The Royal Society of Chemistry.Scopu