Triple Layer Tungsten Trioxide, Graphene, and Polyaniline Composite Films for Combined Energy Storage and Electrochromic Applications.

Polyaniline (PANI) nanocomposites embedded with manganese iron oxide (MnFe2O4) nanoparticles were prepared as thin films by electropolymerizing aniline monomers onto indium tin oxide (ITO) glass slides pre- spin-coated with MnFe2O4 nanoparticles. The UV-visible absorption spectra, FT-IR and SEM results confirmed the formation of the composite films and the chemical interaction between the PANI matrix and MnFe2O4 particles. A coloration efficiency of 206.2 cm2 C-1 was obtained for the PANI/MnFe2O4 nanocomposite film, higher than that of the pristine PANI film, 104.2 cm2 C-1, suggesting a synergistic effect between the MnFe2O4 particles and the PANI matrix. An enhanced areal capacitance as 4.46 mF cm-2 was also achieved in the PANI/MnFe2O4 nanocomposite film compared with that of 3.95 mF cm-2 in the pristine PANI film from the CV at a scan rate of 5 mV s-1. The enhanced capacitance of the composite films are attributed to the pseudocapacitive property of MnFe2O4 and the rougher morphology caused by the embedment of MnFe2O4 particles into the PANI matrix. Finally, the positive roles of decreasing H2SO4 concentration and increasing temperature during a low temperature range were also demonstrated, however relative higher temperatures can destroy the PANI structure and cause the degradation of PANI. Experimental 1.0 mg Mn2FeO4 was dissolved in 10.0 mL ethanol solution under sonication. The MnFe2O4 film was prepared by drop casting about 1.0 mL MnFe2O4 suspension onto the ITO glass and maintained at 2000 rpm for 20 s. The film was dried naturally overnight. The electropolymerization of aniline onto the as-treated ITO glass or formed MnFe2O4 film was performed on an electrochemical working station VersaSTAT 4 potentiostat (Princeton Applied Research). A typical three electrode electrochemical cell was employed, in which a saturated calomel electrode (SCE) served as the reference electrode, a platinum (Pt) wire served as the counter electrode and the MnFe2O4 coated ITO glass or bare ITO glass slide with an effective area of 4.0 cm2 served as the working electrode. A long path length home-made spectroelectrochemical cell was used for optical characterizations. A typical electrochemical polymerization was performed 10 cycles scanned back and forth from 0 to +1.2 V vs. SCE at a scan rate of 50 mV/s in 0.5 M H2SO4aqueous solution containing 0.1 M aniline. Results and Discussion A fewer amount of PANI was deposited on the MnFe2O4 layer due to the increased resistance caused by the introduced MnFe2O4. The relationship between MnFe2O4 and PANI is probably caused by the π-π stacking, electrostatic interactions as well as hydrogen bonding between MnFe2O4 and the -NH group in PANI. The higher coloration efficiency and stable chronocoulometry of MnFe2O4/PANI nanocomposite further confirm the positive role of MnFe2O4 layer. Enhanced capacitance of MnFe2O4/PANI nanocomposite is probably due to the supercapacitive role of MnFe2O4 and resulted rougher morphology. Enhanced capacitances were obtained when increasing temperature in low temperature range and decreasing H2SO4concentration. Conclusion A PANI matrix embedded with MnFe2O4 particles nanocomposite film was successfully prepared by an electrodeposition of PANI monomer onto a MnFe2O4 coated ITO glass. Multi-color electrochromic phenomenon, higher coloration efficiency and faster switching response were obtained due to the major PANI and the inner interactions between the PANI matrix and the MnFe2O4 particles as well as the resulted rougher morphology. The PANI/MnFe2O4 nanocomposite film also exhibits an enhanced areal capacitance compared to that of the pristine PANI film at low scan rates due to the capacitive role of MnFe2O4. A negative role of increasing the H2SO4 concentration and a positive role of increasing temperature on the supercapacitive behaviors of both the pristine PANI and PANI/MnFe2O4 composites films was also demonstrated. Acknowledgments The financial supports from University of Tennessee Knoxville are kindly acknowledged. Figure 1. CV curves of pureMnFe2O4 film, pristine PANI film and PANI/MnFe2O4 nanocomposite film onto ITO glass in 1.0 M H2SO4 at a scan rate of 5 mV/s. Background is the TEM image of PANI/MnFe2O4nanocomposite accompanied with the color changing phenomenon.

Metal-organic frameworks (MOFs) deliver potential applications in electrochromism and energy storage. However, the poor intrinsic conductivity of MOFs in electrolytes seriously hampers the development of the above-mentioned electrochemical applications, especially in one MOF electrode. Herein, a new Ni-based MOF (denoted Ni-DPNDI) is proposed with enhanced conductivity by π-delocalized DPNDI connectors. Predictably, the obtained Ni-DPNDI MOF achieves a conductivity of up to 4.63 S∙m-1 at 300 K. Profiting from its unique electronic structure, the Ni-DPNDI MOF delivers excellent electrochromic and energy storage performance with a great optical modulation (60.8%), a fast switching speed (tc = 7.9 s and tb = 6.4 s), a moderate specific capacitance (25.3 mAh·g-1) and good cycle stability over 2000 times. Meanwhile, energy storage capacity is visual by the coloration states of Ni-DPNDI film. As a proof of the potential application, a large-area (100 cm2) electrochromic energy storage smart window is further designed and displayed. The strategy provides an interesting alternative to porous multifunctional materials for the new generation of electronic devices with diverse applications.

Ternary composite of unzipped multiwalled carbon nanotubes (curved graphenes) for next-generation capatteries.

Cerium oxide (CeO2) photo/electrocatalysts for energy storage and environmental applications have attracted considerable interest because of stable crystal structure, low toxicity/cost, superior chemical stability, stable redox (Ce3+/Ce4+) pairs, abundant oxygen defects, and capablility for intense interaction with other materials. However, the wide bandgap and poor conductivity lower the CeO2 photo/electrocatalytic and energy storage performances. To overcome these limitations, various modification strategies (tuning morphology, doping or loading of metal nanoparticles, and heterostructures) have been applied for the improvement of photocatalytic (removal of organic contaminants from water/wastewater and H2 production and CO2 reduction reactions) efficiency, electrocatalytic (hydrogen/oxygen evolution reactions and CO2 reduction reactions), and energy storage performances (supercapacitor) of CeO2‐based materials. Herein, the recent progress of CeO2‐based materials for electro(photo)catalysis and energy storage applications has been discussed. The challenges and possible direction of CeO2‐based materials for electro(photo)catalysis and energy storage applications have been emphasized. Furthermore, this comprehensive review is expected to advance the design of CeO2‐based materials and their applications in electro(photo)catalysis and energy.

Smart windows, capable of modulating near-infrared (NIR) and visible light, have gained significant attention for enhancing indoor comfort and privacy while integrating energy storage functionalities. Transition metal oxides, particularly tungsten oxides, are widely used in electrochromic applications, but often suffer from limitations such as low coloration efficiency (C.E.) and slow response times. This study explores the incorporation of Ti3C2Tx MXene into oxygen-deficient tungsten oxide (W18O49) to enhance electrochromic and energy storage performance. By optimizing solvothermal synthesis through solvent variation, a 5 wt.% Ti3C2Tx-W18O49 composite (5MX-WO) is developed, exhibiting superior electrochromic properties with 72% optical modulation at 700nm, rapid switching speeds (6.5s coloration, 5.6s bleaching), high C.E. (≈182cm2C-1 at 700nm), and areal capacitance of 25mFcm-2 at 0.5mAcm-2. The presence of Ti3C2Tx facilitates enhanced electronic and ionic transport pathways, contributing to optimal electrochromic behavior. A complementary electrochromic device (CECD) of size ≈5 × 5cm2 is fabricated using 5MX-WO as the working electrode and spray-coated NiO as the counter electrode. The device achieved 61% optical modulation at 850nm, fast response times, and excellent cyclic stability over 1000 cycles. These findings underscore the potential of W18O49/Ti3C2Tx composites for next-generation electrochromic energy storage systems.

A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

Bi-functional flexible electrodes based on tungsten trioxide/zinc oxide nanocomposites for electrochromic and energy storage applications

Efficient energy storage performance of electrochemical supercapacitors based on polyaniline/graphene nanocomposite electrodes

Investigating the synergistic characteristics of air processable CsPbIBr₂ perovskite electrodes for solar cell and energy storage applications

Core-shell nanomaterials: Applications in energy storage and conversion

The dual-functional device combining electrochromic properties and energy storage has gained numerous attentions in the field of energy-saving smart electronics. However, achieving simultaneous optimization of coloration efficiency and energy storage capacity of materials poses a significant challenge. This study presents a novel approach by incorporating methyl orange into Prussian blue channels (PB-MO films) to adjust the internal electronic structure of Prussian blue. This modification allows the active layer to simultaneously improve the electrochromic and energy storage performance. The introduction of methyl orange not only alters the ratio of Fe3+/Fe2+ within the framework through the coordination reaction of Fe3+ with methyl orange, but also improves the reaction kinetics after intercalating organic dye molecules, including charge transfer resistance, diffusion capability of ions and capacitive contribution. The PB-MO films demonstrate remarkable properties: high optical contrast (81.4% at 670nm), excellent coloration efficiency (265 cm2C-1), and significant specific capacity (84 mAh m-2 at 0.05 A m-2), outperforming pure PB films. The PB-MO films are ideally suited for applications in displays and intelligent energy storage fields, boasting both high coloration efficiency and substantial energy storage capacity, thus advancing promote the development of dual-functional electrochromic devices.

The dramatic environmental pollution and energy shortages have spurred internationally unprecedented interest in developing new energy technologies. Supercapacitors have emerged as a new class of green electrochemical devices for energy conversion and storage and are promising candidates for extensive applications. As a key component of supercapacitors, electrode materials are a crucial factor to the electrochemical performance based on its properties including surface area, pore structure, conductivity and surface functionalization. The well-designed synthesis strategies and conditions are usually fatal to tailor four mentioned properties. Due to the advantages of low cost, high specific surface area and conductivity, controllable microstructure, easy surface functionalization, remarkable chemical stability and outstanding electrolyte ion accessibility, porous carbon materials tailored through well-designed synthesis strategies and conditions, exhibit high energy density and power density as well as superb electrochemical cycling stability. In this review, we firstly provide a brief description of energy storage mechanisms for different types of electrode materials, followed by a comprehensive overview of recent advances in development of different carbon-based materials with activated carbon, carbon aerogels, carbon fiber, mesoporous carbon, carbon nanotube and graphene. Then we state the key parameters to evaluate the electrochemical properties, such as specific capacitance, energy density and power density, and also discuss the relationship between the influence parameters (e.g. surface area, pore structure, conductivity, and surface properties) and enhanced performances. Further, according to the research work of our group, we present a summary on the design, synthesis and applications in energy conversion and storage based on porous carbon materials, including carbons with different pore distributions (hierarchical porous carbon, porous carbon sphere, ultramicroporous carbon), functionalized porous carbon and porous carbon composite materials. In terms of carbons with different pore distributions, we list some characteristic synthetic methods (e.g. the self-template strategy for banana-peel-derived hierarchical porous carbon foams, the seeded synthetic strategy for phenolic-resin-derived porous carbon nanospheres and the solvothermal method for phloroglucinol-terephthaldehyde-derived ultramicroporous carbon nanoparticles), which can be concluded that micropores (especially ultramicropores) are electrochemically available for electrolyte ions because the solvation shell is squeezed through the pores less than the solvated ion size and such distortion reduces distance between the electrode surface and the ion center, while mesopores offer highly efficient pore channels for ion penetration and transport. In terms of functionalized porous carbon, we adopt the in situ synthesis approach to prepare nitrogen-doped carbons ( e.g. poly(1, 5-diaminonapthalene)-derived nitrogen-containing carbon microspheres and phenylenediamine-terephthalaldehyde-derived nitrogen-functionalized microporous carbon nanoparticles), which demonstrate that heteroatom doping, on the one hand, increases the surface wettability in the aqueous electrolyte to improve the mass transfer efficiency, and on the other hand, endows additional psedocapacitance for the electrode. In terms of porous carbon composite materials, we combine carbon-based materials with pseudocapacitive metal oxides (e.g. NiO and MnO2) for achieving high-performance supercapacitors, which is a wise choice to increase the energy density without sacrificing the high power capability. These strategies and methods provide new ideas to simple and highly efficient design of porous carbon materials and may be extendable to other systems such as metal or metal oxide materials. Additionally, the future trend of carbon based electrode materials for energy conversion and storage device is discussed. There are extensive applications outside the area of high-rate electrochemical energy storage, such as drug delivery, photonic crystals, adsorption and separation, and catalysis.

Electrodeposition of Ag nanoparticles on conductive polyaniline/cellulose aerogels with increased synergistic effect for energy storage

We report the fabrication of NiO nanoflake-based bifunctional glass electrodes that combine energy storage and electrochromism.

Exploring innovative synthetic solutions for advanced polymer-based electrochromic energy storage devices: Phenoxazine as a promising chromophore