Solar Energy Storage Applications Research Articles

Novel MoS2/montmorillonite hybrid aerogel encapsulated PEG as composite phase change materials with superior solar-thermal energy harvesting and storage

Phase change materials (PCMs) offer significant advantages in energy conversion and storage by facilitating the storage and release of thermal energy during phase transition processes. However, challenges such as leakage during PCM phase transitions and poor light absorption properties have constrained their application in the field of photothermal energy storage. In this study, Montmorillonite (Mt) and molybdenum disulfide (MoS2) has been used to design and synthesize hybrid aerogels (MoS2/Mt) boasting high mechanical strength and excellent photothermal conversion performance. These aerogels are then used to encapsulate polyethylene glycol (PEG) to prepare composite PCMs with outstanding solar-thermal conversion and storage performances. The results show that the synthesized MoS2/Mt-PEG composite PCMs exhibit high enthalpies of melting and solidification of 169.16 J/g and 170.78 J/g, respectively, while the aerogel supporting material has a high compressive modulus of 1.96 MPa. Moreover, the composite material displayed excellent thermal stability and leakage resistance after undergoing 30 melting-cooling cycles. Furthermore, the incorporation of MoS2 imparted outstanding light absorption properties to the MoS2/Mt-PEG composite, resulting in a high light absorption and photothermal conversion-storage efficiency of 93.4 % and 96.47 %, respectively. Synthesized composite PCMs also demonstrate outstanding performance in solar-thermal-electricity conversion, achieving a voltage output of 458 mV under illumination conditions and maintaining a sustainable voltage output even after removing the light source. Thus, the composite PCMs prepared in this work can meet the requirements of high enthalpy, effective leakage prevention, efficient solar-thermal conversion and solar-thermal-electricity conversion performance, thereby presenting potential applications in practical solar energy collection, conversion, and storage.

The first principles insights of aluminum-based hydrides for hydrogen storage application

Hydrogen storage is an urgent issue for mobile applications, to overcome this issue solid materials have a potential role for hydrogen storage applications. Moreover, the perovskite hydride materials have been extensively investigated for improvement in the field of hydrogen storage. However, this work is focused on the computational study of XAlH3 (X: Na, Mg) perovskite-type hydrides for different physical properties and hydrogen storage applications. Both materials were found thermodynamically, and mechanically stable from the negative formation energy and elastic properties. They exhibited cubic phases with computed lattice constants are 3.827 Å and 3.752 Å, respectively. The electronic properties indicated that both compounds have a metallic nature, and found the high contribution of Al-p state, and H-1s state near the Fermi level. However, the Hirshfeld net charge analysis detected, that charge transfer from Al and X (Na, Mg) atoms to H atoms. Furthermore, the metallic hydrides have promised candidates for hydrogen storage applications. Both compounds have observed non-magnetic behavior with zero magnetic moments. Elastic constants were calculated to determine the mechanical stability of the compounds, it was found that MgAlH3 is harder than NaAlH3, and it exhibited that higher Bulk, Shear, and Young's modulus. The Poisson's, and Pugh's (G/B) ratios suggested that ionic boning of the atoms, additionally, Pugh's ratio (B/G) and Cauchy pressure (Cp) confirmed that NaAlH3 ductile and MgAlH3 is brittle behavior. Besides this, Optical properties were determined for both compounds including the dielectric function, conductivity, refractive index, absorption, and loss function. It is found that the MgAlH3 compound optical more suitable than NaAlH3 due to calculated optical factors promised and both compounds are undertaken for solar cells, optoelectronics, and energy storage applications. Finally, the computed hydrogen storage capacity for NaAlH3 and MgAlH3 compounds are 6.01 wt%, and 5.56 wt% respectively. These results revealed that both have the potential materials for hydrogen storage, but NaAlH3 unique material to fulfill the US-DOE criteria of 2020.

Valence shell electronically excited states of norbornadiene and quadricyclane.

The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8eV using the Fourier transform spectrometer at the SOLEIL synchrotron radiation facility. The absorption spectrum of NBD exhibits some sharp structure associated with transitions into Rydberg states, superimposed on several broad bands attributable to valence excitations. Sharp structure, although less pronounced, also appears in the absorption spectrum of QC. Assignments have been proposed for some of the absorption bands using calculated vertical transition energies and oscillator strengths for the electronically excited states of NBD and QC. Natural transition orbitals indicate that some of the electronically excited states in NBD have a mixed Rydberg/valence character, whereas the first ten excited singlet states in QC are all predominantly Rydberg in the vertical region. In NBD, a comparison between the vibrational structure observed in the experimental 11B1-11A1 (3sa1 ← 5b1) band and that predicted by Franck-Condon and Herzberg-Teller modeling has necessitated a revision of the band origin and of the vibrational assignments proposed previously. Similar comparisons have encouraged a revision of the adiabatic first ionization energy of NBD. Simulations of the vibrational structure due to excitation from the 5b2 orbital in QC into 3p and 3d Rydberg states have allowed tentative assignments to be proposed for the complex structure observed in the absorption bands between ∼5.4 and 7.0eV.

Statistical analysis of radiative solar trough collectors for MHD Jeffrey hybrid nanofluid flow with gyrotactic microorganism: entropy generation optimization

PurposeA parabolic trough solar collector is an advanced concentrated solar power technology that significantly captures radiant energy. Solar power will help different sectors reach their energy needs in areas where traditional fuels are in use. This study aims to examine the sensitivity analysis for optimizing the heat transfer and entropy generation in the Jeffrey magnetohydrodynamic hybrid nanofluid flow under the influence of motile gyrotactic microorganisms with solar radiation in the parabolic trough solar collectors. The influences of viscous dissipation and Ohmic heating are also considered in this investigation.Design/methodology/approachGoverning partial differential equations are derived via boundary layer assumptions and nondimensionalized with the help of suitable similarity transformations. The resulting higher-order coupled ordinary differential equations are numerically investigated using the Runga-Kutta fourth-order numerical approach with the shooting technique in the computational MATLAB tool.FindingsThe numerical outcomes of influential parameters are presented graphically for velocity, temperature, entropy generation, Bejan number, drag coefficient and Nusselt number. It is observed that escalating the values of melting heat parameter and the Prandl number enhances the Nusselt number, while reverse effect is observed with an enhancement in the magnetic field parameter and bioconvection Lewis number. Increasing the magnetic field and bioconvection diffusion parameter improves the entropy and Bejan number.Originality/valueNanotechnology has captured the interest of researchers due to its engrossing performance and wide range of applications in heat transfer and solar energy storage. There are numerous advantages of hybrid nanofluids over traditional heat transfer fluids. In addition, the upswing suspension of the motile gyrotactic microorganisms improves the hybrid nanofluid stability, enhancing the performance of the solar collector. The use of solar energy reduces the industry’s dependency on fossil fuels.

Performance improvement of phase change materials encapsulated with graphene oxide for thermal storage

The thermal enhanced phase change microcapsules were prepared by paraffin as core material and the modified graphene as wall material. X-ray diffraction (XRD) and Fourier transform infrared spectroscope (FTIR) were applied to determine the microstructure and chemical structure of the microcapsules. A differential scanning calorimeter (DSC) test was done to investigate the thermal properties and thermal stability of the microcapsules. The results showed that the modified graphene/paraffin microcapsules have a regular spherical shape. The thermal conductivity of the microcapsules increases gradually with the increase of the content of the modified graphene. When the content of graphene content is 10 %, the thermal conductivity of the microcapsules is 4.01 times that of paraffin. The enthalpy of phase transition of the microcapsules is 100.3 J/g. Considering the suitable thermal properties, good thermal reliability, chemical stability and great thermal conductivity of the prepared microcapsules, it shows good application prospects in thermal or solar energy storage applications.

Prussian blue analogues with Na2NixCoyMnzFe(CN)6-multimetallic structures as positive and hydrogen vanadate as negative electrodes in aqueous Na-ion batteries for solar energy storage applications

Multiple N-coordinated transition metals in Prussian blue analogues provide synergistic effects on the energy storage mechanisms. A Na-ion solar battery with Na2Ni0.33Co0.33Mn0.33Fe(CN)6//H2V3O8 configuration depicts satisfactory performances.

Thermal energy storage behaviour of form-stable polyethylene glycol/MWCNT- based phase change materials

Organic phase change materials (OPCMs) possess a remarkable ability to absorb and release latent heat during phase transitions, making them very promising for storing solar energy. Nevertheless, the extensive use of these materials encounters substantial obstacles arising from intrinsic difficulties, such as limited heat conductivity and chemical stability concerns. The authors of this innovative work have successfully led the way in developing a state-of-the-art nano-enhanced organic phase change material (Ne-OPCM). This novel substance utilizes polyethylene glycol (PEG) as the primary phase transition material, which is smoothly incorporated into a network of polymethyl methacrylate (PMMA) to reduce obstacles caused by molecular size and improve chemical durability. In order to overcome the issue of poor thermal conductivity, the researchers selectively used multi-walled carbon nanotubes (MWCNT) as a conductive filler. This resulted in a significant increase in the thermal conductivity of PEG-1000. In an ongoing study, thermal characteristics of the developed (Ne-OPCM) composites are evaluated for different weight fractions of 0.3 %, 0.7 %, and 1.0 % of MWCNT. In addition to the morphology, thermal property, chemical stability, optical absorptivity and the latent heat of the developed PEG-PMMA/MWCNT (Ne-OPCM) composite are evaluated using FESEM, FT-IR, UV-Vis spectroscopy TGA and DSC instruments. The thermal conductivity of PEG-PMMA/MWCNT (Ne-OPCM) composite was improved by 87.64 % with a dispersion of 0.7 wt% of MWCNT. The DSC conducted highest latent heat and melting point of a PEG-PMMA/MWCNT (NePCM) composite are 139.66 J/g & 40.4 °C occurring at 0.7 wt% of MWCNT. Consequently, the developed (Ne-OPCM) composites have promising potential in practical solar energy storage applications at the temperature range of 35-40 °C.

Enhanced thermal storage and photo-thermal conversion composite phase change materials based on MOF-derived carbon for efficient solar energy utilization

Composite phase change materials (PCMs) with high thermal conductivity and photo-thermal conversion performance can be employed for the efficient conversion and utilization of solar energy. In this work, a Ni-doped carbon material derived from a Ni metal-organic framework (Ni-BTC) is prepared and used as the supporting material to encapsulate polyethylene glycol (PEG). The Ni-BTC derived carbon (NBC) obtained retained the intrinsic porous flower-like structure which facilitates the encapsulation of PEG. The doping of Ni metal particles enhances both the thermal conductivity and photo-thermal conversion performance of the composite PCM. Additionally, the thermal conductivity of the composite PCM is further enhanced by the addition of a graphene/Ag composite, resulting in a thermal conductivity that is 3.15 times higher than that of pure PEG. The latent heat of the resulting composite PCM is 125.4 J/g, the photo-thermal conversion efficiency is 91.81 %. Moreover, the composite PCM exhibits excellent thermal stability and reliability, indicating its potential for wide-ranging applications in solar energy storage.

MXene-based eutectic salt hydrate phase change material for efficient thermal features, corrosion resistance & photo-thermal energy conversion

Salt hydrate phase change materials (PCMs) possess low thermal conductivity, degree of supercooling, lack of corrosion resistance and poor photo thermal conversion ability. To overcome these challenges, a two dimensional, chemically stable, optically & thermally efficient MXene@eutectic salt hydrate composite PCM is developed for effective harnessing of solar energy and thermal energy storage (TES) applications. Low temperature eutectic salt hydrate PCM with phase transition temperature of 27.6 °C and 216 J/g melting enthalpy is developed using sodium sulphate decahydrate (SSD) and sodium phosphate dibasic dodecahydrate (SPDD) based on Schrader equation. Advanced 2D layered material, MXene (Ti3C2) is synthesised from MAX phase (Ti3AlC2). Furthermore, MXene based PCM nanocomposite is developed with binary eutectic PCM of SSD/SPDD at different weight fractions through two step technique. Developed nanocomposite PCM exhibits better chemical stability, high optical absorbance of (1.1), low transmissibility (10.2 %), reliable thermal conductivity (0.621 W/m⋅K), improved melting enthalpy (161.2 J/g) and considerable cycle stability. The optical absorbance and thermal conductivity demonstrated a superior photo-thermal conversion capability and thermal networks for the developed MXene based composite sample at 0.9 wt% of MXene. The above properties are experimentally inferred by evaluating the developed MXene@ eutectic salt hydrate and base eutectic PCM under the solar simulator. The interfacial attraction between the two dimensional MXene nano flakes and the developed eutectic PCM ensures a promising ability to trap solar energy effectively for thermal regulation in a sustainable direction. Subsequently, the effect of MXene with SSD/SPDD in regard to the issue of corrosion is explored for copper and aluminium metal surface.

Advancements in Phase Change Materials: A Path to Sustainable Energy Solutions in China

With the rapid development of China, the country's demand for energy has significantly increased. According to the "World Energy Outlook 2020," China's annual average growth rate of primary energy consumption is 1.9%, and it is predicted that China's energy consumption will account for over 20% of global energy consumption by 2050. In the energy budget, 90% is allocated to thermal energy conversion, transmission, and storage. Facing an impending energy crisis, enhancing energy production while minimizing energy loss has become a matter of widespread concern. Phase Change Materials (PCMs), also called phase change energy storage materials, have garnered attention as a novel energy-efficient and environmentally friendly material. PCMs refer to substances that undergo a change in state and provide latent heat without changing their temperature. Phase change thermal storage materials utilize phase transitions during heat exchange processes to store energy by means of these phase changes. Compared to chemical energy storage materials, PCMs offer high thermal efficiency and energy storage density, maintain constant temperature, and are more easily controllable. They hold great potential as a promising material in the field of thermal energy storage and have been widely applied in areas such as solar energy, lithium batteries, building insulation, and medical applications. This article offers a comprehensive overview of the principles and classification of Phase Change Material (PCM), including organic PCM, inorganic PCM, and composite PCM. It discusses their applications in solar thermal energy storage, cooling of photovoltaic panels, building materials, and industrial waste heat recovery. The article also highlights China's research and development efforts in these areas, emphasizing the country's significant contributions to advancing PCM technology.

Eco-friendly synthesis of chemically cross-linked chitosan/cellulose nanocrystal/CMK-3 aerogel based shape-stable phase change material with enhanced energy conversion and storage

Phase change materials (PCMs) have attracted numerous attention owing to their high energy storage density, cost-effective and operationally simple, however, the “solid-liquid” leakage and limited solar absorbance seriously hinder their widespread applications. Herein, an innovative chitosan/cellulose nanocrystal/CMK-3 (CS/CNC/CMK-3) aerogel based shape-stable PCM (SSPCM) was successfully synthesized, in which chemically cross-linked CS and CNC acted as three-dimensional supporting skeleton, CMK-3 endowed solar-to-thermal energy conversion ability and the impregnating polyethylene glycol (PEG) acted as the latent heat storage unit. The as-synthesized CS/CNC/CMK-3 aerogel/PEG (CCCA/PEG) showed ultrahigh melting/crystallization enthalpy of 178.5/171.1 J g−1 and excellent shape stability. The PEG was effectively embedded into the hierarchical porous architecture and the composite PCM could preserve its original shape without any leakage even compressed above the melting point of PEG. Meanwhile, the CCCA/PEG exhibited robust thermal reliability with an ultralow enthalpy fading rate of 0.030 ± 0.012 % per cycle over 100 thermal cycles. Intriguingly, the introduction of CMK-3 also significantly improved the solar-to-thermal energy conversion performance of CCCA/PEG, and a high solar-to-thermal conversion efficiency of 93.1 % could be realized. This work provided a potential strategy to design and synthesize high-performance sustainable SSPCM, which showed tremendous potential in the practical solar energy harvesting, conversion and storage applications.

Augmenting the thermal response of helical coil latent-heat storage systems with a central return tube configuration

Low-temperature stratification, high-volumetric storage capacity, and less-complicated material processing make phase-changing materials (PCMs) very suitable candidates for solar energy storage applications. However, their poor heat diffusivities and suboptimal containment designs severely limit their decent storage capabilities. In these systems, the arrangement of tubes conveying the heat transport fluid (HTF) plays a crucial role in heat communication between the PCM and HTF during phase transition. This study investigates a helical coil tube-and-shell thermal storage system integrated with a novel central return tube to enhance heat transfer effectiveness. Three-dimensional computational fluid dynamics simulations compare the proposed design against a baseline helical coil system without a return tube under equivalent conditions. Outcomes quantify the return tube's efficacy in augmenting heat transfer uniformity and accelerating phase transition. Adding the return tube markedly boosts heat storage and recovery rates, increasing charging by 88% and discharging by 56% versus the baseline. Moreover, total phase transition time reduces by 48% for melting and 36% for solidification with the return tube. The accelerated charging stems from sustained convective heat transfer inside the return tube even as the molten layer thickens. Meanwhile, enhanced solidification results from ongoing cooling of inner regions. Isotherm analysis visualizes the return tube's efficacy in maintaining thermal uniformity throughout the phase transition process. Overall, the return tube significantly improves PCM thermal response, demonstrating a novel but straightforward approach to address heat transfer limitations in latent thermal storage systems.

Combining heterointerface/surface oxygen vacancies engineering of bismuth oxide to synergistically improve its solar water splitting performance

Solar-powered photoelectrochemical (PEC) water splitting is recognized as a strategy for addressing fossil resource and global warming concerns. The purpose of this paper is to demonstrate for the first time a facile method to fabricate dendritic nanostructured (DN) Bi:Bi2O3 heterointerface engineering junctions that possess abundant surface oxygen vacancies (OVs, DN Bi:Bi2O3-OVs/FTO), with outstanding PEC performance. The surface OVs serve as shallow donors and active reaction sites, whereas the Bi-metal bridges are used for fast electron transport. Furthermore, surface OVs can enhance the surface features of Bi:Bi2O3 heterointerfaces and boost their electrical conductivity and donor density. This greatly enhances electrolyte ion and electron mobility, resulting in rapid water oxidation reactions at the Bi:Bi2O3/electrolyte interfaces. By combining the Bi:Bi2O3 heterointerface junction and surface OVs, we are able to create an effective photoanode with 95 % charge injection efficiency, applied bias photon-to-current efficiency (ABPE) of 0.112 %, and a photocurrent response of 0.334 mA.cm−2 at 1.23 V vs. the reversible hydrogen electrode (RHE), which represents improvements of about 4.5 and 10 folds over that of pure DN Bi2O3 photoanode. It is possible to construct a variety of unique nanostructured electrodes with adjustable optical and electronic properties to be used in solar cells, energy storage, and PEC applications.

Experimental heat transfer study of an enhanced storage medium

Phase change materials (PCMs) are suitable for storing solar energy due to their high-density energy storage and ability to operate in a wide range of temperatures. However, the lower thermophysical properties of PCMs limit their use in solar energy storage applications. Therefore, the incorporation of nanoparticles has emerged as a promising technique to enhance the storage density of PCMs.Extensive studies have been conducted on the measurement of thermophysical properties of both PCMs and nano-PCMs (PCMs with nanoparticles dispersed in them). However, there has been no comprehensive study covering the following aspects: (a) the measurement of thermophysical properties of NaNO3 (PCM) and nano-NaNO3 (nano-PCM), (b) solar energy storage of NaNO3 involving both sensible heat and latent heat in the same study, (c) the construction and implementation of an experimental rig capable of studying heat transfer in PCM and nano-PCM for solar energy storage applications (with a maximum temperature of up to 350 °C), and (d) investigating the effect of nanoparticles on large-scale solar energy storage systems. Therefore, the aim of this study is to experimentally investigate all of the aforementioned points. In order to develop and test these solar storage mediums, an experimental setup has been designed and manufactured, as mentioned earlier.Furthermore, limited studies have considered sodium nitrate salt (NaNO3) as a PCM. In this study, NaNO3 is used as the base material, and two types of materials are considered: PCM1, which consists of sodium nitrate salt (NaNO3), and PCM2, which consists of sodium nitrate salt (NaNO3) with 0.75 wt% iron oxide nanoparticles (Fe2O3) added. The experiments conducted involved both steady-state and transient conditions. The results showed that the addition of nanoparticles improved the charging and discharging by 25.6 % and 23.929 %, respectively. Moreover, the specific heat capacity and latent heat of the developed PCMs increased by 17.857 % and 9.97 %, respectively. These findings suggest that PCM2, with the presence of nanoparticles, melts and discharges energy faster compared to PCM1. Overall, this study contributes to the understanding of solar energy storage using PCMs and nano-PCMs, highlighting the potential benefits of nanoparticle incorporation in enhancing their performance.

Nanofluid bioconvective transport for non-Newtonian material in bidirectional oscillating regime with nonlinear radiation and external heat source: Applications to storage and renewable energy

The enhanced thermal performances of nanofluids reports different applications in solar systems energy storage and renewable energy. The renewable enhancement in thermal management systems is predicted in recent years. Following such motivations of nanomaterials in the renewable systems, the objective of current wok is to present nanofluid flow with suspension of non-Newtonian material with additional impact of external heating source. The Williamson nanofluid is signifies to suggests the rheological impact of nonlinear material. The stability of nanofluid is reported with bioconvection assessment due to microorganisms. The thermal model is further modified in view of nonlinear radiative electromagnetic source and activation energy. Time dependent flow is induced due to bidirectional accelerating surface with uniform magnitude. The formulation of problem is based in partial differential systems. The solution procedure is based on analytical homotopy analysis technique. The thermal outcomes in variation of parameters are observed. It is claimed that external heat presentation can boosted the thermal profile more exclusively. With increasing the Williamson fluid parameter, the heat and mass transfer phenomenon can be improved.

An Enduring Na-Ion Solar Battery Configured with Na2Co0.5Ni0.5Fe(CN)6 Positive and NaTi2(PO4)3 Negative Electrodes in Na2SO4-SiO2 Hydrogel Electrolyte

A successful solar energy storage is accomplished in a 5 V/5 mAh rated Na-ion battery, which is customized by series connection of three 1.8 V unit cells. The unit cell is constructed with open framework structured Na2Co0.5Ni0.5Fe(CN)6 positive and Natrium Super Ionic CONductor (NaSICON) type NaTi2(PO4)3 negative electrodes in 1 M Na2SO4-SiO2 hydrogel electrolyte. Both positive and negative active materials demonstrate Faradaic charge storage mechanism with appreciable diffusion coefficients, such as 5.17 × 10−15 and 1.13 10−15, respectively. The Na2Co0.5Ni0.5Fe(CN)6//NaTi2(PO4)3 full cell depicts a specific capacity of 48 mAh g−1 (@ 100 mA g−1), an energy density of 95.68 Wh kg−1 (@ 259.96 W kg−1) and a power density of 779.75 W kg−1 (@ 54.36 Wh kg−1). The cell also exhibits an excellent durability, i.e., 93% capacity retention with 99% Columbic efficiency at 200 mA g−1 upon 1000 cycles. However, the 5 V battery is performance tested under solar-charging cum constant-load-discharging experiment for one-month, and the device describes 85% capacity retention over the period. The good power capability and cycle life with moderate energy density make this battery chemistry suitable for solar energy storage applications.

Fundamental Understanding on Selenium Electrochemistry: From Electrolytic Cell to Advanced Energy Storage

Selenium (Se), as an important quasi‐metal element, has attracted much attention in the fields of thin‐film solar cells, electrocatalysts and energy storage applications, due to its unique physical and chemical properties. However, the electrochemical behavior of Se in different systems from electrolytic cell to battery are complex and not fully understood. In this article, we focus on the electrochemical processes of Se in aqueous solutions, molten salts and ionic liquid electrolytes, as well as the application of Se‐containing materials in energy storage. Initially, the electrochemical behaviors of Se‐containing species in different systems are comprehensively summarized to understand the complexity of the kinetic processes and guide the Se electrodeposition. Then, the relationship between the deposition conditions and resulting structure and morphology of electrodeposited Se is discussed, so as to regulate the morphology and composition of the products. Finally, the advanced energy storage applications of Se in thin‐film solar cells and secondary batteries are reviewed, and the electrochemical reaction processes of Se are systematically comprehended in monovalent and multivalent metal‐ion batteries. Based on understanding the fundamental electrochemistry mechanism, the future development directions of Se‐containing materials are considered in view of the in‐depth review of reaction kinetics and energy storage applications.

Nanosecond Intra-Ionic Chloride Photo-Oxidation.

Transition-metal photocatalysts capable of oxidizing chloride are rare yet serve as an attractive means to controllably generate chlorine atoms, which have continued to garner the interest of researchers for notable applications in photoredox catalysis and solar energy storage. Herein, a new series of four Ir-photocatalysts with different dicationic chloride-sequestering ligands were synthesized and characterized to probe the relationship between chloride binding affinities, ion pair solution structures, and rate constants for chloride photo-oxidation in acetonitrile at room temperature. The substituents on the quaternary amines of dicationic bipyridine ligands had negligible effects on the photocatalyst excited-state reduction potential, yet dramatically influenced the affinity for chloride binding, indicating that synthetic design can be utilized to independently tune these important properties. An inverse correlation was observed between the equilibrium constant for chloride ion pairing and the rate constant for intra-ionic chloride oxidation. Exceptions to this trend suggest structural differences in the ion-paired solution structures, which were probed by 1H NMR binding experiments. This study provides new insights into light-induced oxidation of ion-paired substrates, a burgeoning approach that offers to circumvent diffusional constraints of photocatalysts with short excited-state lifetimes. Ground-state association of chloride with these photocatalysts enables intra-ionic chloride oxidation on a rapid nanosecond timescale.

Crystallization and additional oxide interlayers improve the tribocorrosion resistance of TiO2 nanotubular surfaces formed on Ti6Al4V

TiO2-based nanotubular surfaces have promising properties for various industrial applications, such as solar cells, fuel cells, photocatalysis, energy storage, gas sensors, and biomedical applications. However, they have very limited use in real applications, and one of the major limiting factors is the weak adhesion of nanotubular surfaces to the substrate. In this study, nanotubular surfaces are formed on Ti6Al4V alloy by anodic treatment followed by a heat treatment at 500 °C for 3 h under an open atmosphere. Microstructural investigations revealed self-organized nanotubes grown on both α and β phases. High-resolution TEM/STEM analysis showed crystallization of the nanotubular layer and formation of additional oxide interlayers resulting in a drastic improvement in tribocorrosion resistance. These findings indicated that a simple heat treatment can significantly alter the properties of nanotubular layers and can widen their usage mainly for load-bearing implant applications in corrosive environments.

Hybrid GO/TiO2 nanoparticles reinforced NaAlg/PVA blend: Nanocomposites for high‐performance energy storage devices

AbstractIn this study, novel flexible polymer nanocomposite films formed of polyvinyl alcohol (PVA), sodium alginate (NaAlg), titanium dioxide (TiO2) and graphene oxide (GO) as nanofiller are fabricated by using casting method. The PVA/NaAlg‐GO/TiO2 nanocomposite films are characterized using various techniques. The synergistic effects of GO/TiO2 on the electrical, dielectric properties, and the energy density efficiency of PVA/NaAlg blend have been investigated in the range of frequency from 10 Hz to 7 MHz. The XRD data showed that the intensity of the PVA/NaAlg‐GO/TiO2 nanocomposites films decrease with nanofiller concentration. The FTIR spectroscopy provides proof that the complex formed. The optical studies were carried out using UV–Vis. spectroscopy. The energy bandgap values of PVA/NaAlg‐GO/TiO2 nanocomposite films were calculated using Tauc's plot. It is shown that the host matrix's Eg value decreases from 4.97 to 4.29 eV for direct transitions and from 4.37 to 2.29 eV for indirect transitions. The electrical and dielectric parameters of the nanocomposites showed that the maximum electrical properties were observed for the composite with 8 wt% loading of GO/TiO2. The σdc increased from 2.45 × 10−9 to 5.02 × 10−7 S cm−1. In addition, frequency exponent S decreased from 0.82 to 0.54. These findings demonstrated that there are significant modifications in the fabricated samples, which open the road for utilizing the PVA/NaAlg‐GO/TiO2 nanocomposite as flexible films for solar cells and electrical energy storage applications.