Pure single-crystal rutile-type VO2 has been synthesized via the hydrothermal reaction of V2O5, oxalic acid, and tungstenic acid at low temperatures. The products have been characterized by means of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, selected area electron diffraction, differential scanning calorimetry, and X-ray photoelectron spectroscopy. It is shown that a part of VO2 powders have a “snowflake” morphology assembled by VO2 rods which have a monoclinic structure with a preferential orientation along 110 direction. The adulterating agent tungstenic acid plays a key role in the synthesis of rutile phase. The DSC results indicated that the metal-semiconductor transition temperature of VO2 powders was reduced to room temperature or below. The reaction details and mechanisms are described and discussed. The substitution of a part of V atoms with larger W atoms induces the distortion of the VO6 octahedra, promoting the transition from VO2 (B) to VO2 (R).

Thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) microgel colloids were prepared by using water and high-boiling alcohol as binary solvent. Their thermosensitive behavior and solar modulation ability were studied by differential scanning calorimetery, ultraviolet–visible–near-infrared spectrophotometery, dynamic light scattering, and rheology. Effects of alcohol content and cross-linker dose on their microstructures and optical properties were investigated. A model house was constructed to test their energy-saving performance in smart windows. It was found that the solar modulation ability of PNIPAAm microgel colloids decreased with increasing N,N′-methylenebis(acrylamide) (BIS) dose or alcohol content. Compared to glycol, glycerol showed better compatibility with PNIPAAm hydrogels, inducing less deterioration of the solar modulation ability. With 0.1 wt % (of NIPA) BIS, when glycerol was added as a cosolvent, the prepared PNIPAAm microgel colloids exhibited spherical morphology, controllable LCST, short response time, suitable viscosity, low freezing point, restrained evaporation rate, and excellent energy-saving performance, which makes them much better candidates for application in smart windows than those using a single solvent.

•The VO2 glazing's application performance was demonstrated and simulated.•The demonstration was performed in a full-size room with a 1.65 m×1.65 m window.•The simulation was conducted with a software of high credibility.•The results showed the use of the VO2 glazing could save cooling consumption.As a typical thermochromic material, the vanadium dioxide (VO2) has a great potential for building energy efficiency development. In this study, the VO2 glazing's application performance was first demonstrated in full-size, and simulated with a software of high credibility. For a 2.9 m×1.8 m×1.8 m low-mass room whose window's size is 1.65 m×1.65 m, the measured results showed that the room with the VO2 glazing saved 10.2–19.9% cumulative cooling load than that with an ordinary glazing during the demonstration. The application performance to a conventional residential room in the hot summer and warm winter zone was simulated in BuildingEnergy, a simulation software developed by the authors. The simulated results showed that the use of the VO2 glazing could save ∼9.4% electricity consumption. The effects of the window's orientation and the area ratio of window to wall were also discussed in this study.

•Transparent conductive SnO2:W thin films were fabricated by a solution-based method.•A small addition of W effectively lowered the resistivity of SnO2 films.•The lowest resistivity of 2.8 × 10− 3 Ω · cm was obtained for a SnO2: 3 at% W film.•These films exhibit an optical transmittance of over 80% in the visible region.•These films show the optical band gap ranging from 3.93 to 4.31 eV.High-quality transparent and conductive tungsten-doped tin oxide (SnO2:W) thin films with different thickness (from 60 to 600 ± 10 nm) were fabricated on quartz glass substrates by a solution-based method. A stable solution was prepared from tin chloride and ammonium tungstate together with polyvinyl alcohol as a film-forming promoter. It was found that all films showed homogeneous composition, smooth surface with no cracks and high transparency with the optical band gap ranging from 3.93 to 4.31 eV. The effect of tungsten concentration, spin rate and annealing temperature on the morphological, electrical and optical properties of the films has been investigated. W doping has a large influence on the microstructure and the conductivity of the SnO2 thin films. The lowest resistivity of 2.8 × 10− 3 Ω · cm was obtained for a SnO2: 3 at% W film, which was prepared at 3000 rpm and annealed at 800 °C in air. An eight-layer film with a sheet resistance of 60 Ω/□ and a thickness of 606 nm could be fabricated by multiple coating operation, which still exhibited an optical transmittance of over 80% in the visible region from 400 to 700 nm.

VO2/ATO/polymer thermochromic flexible foils for smart window application were prepared by casting VO2 and Sb : SnO2 (ATO) nanoparticles. The foils exhibit an increased solar-heat shielding ability, causing a 20% decrease in solar transmittance at an ATO content of 9%, while retaining an excellent solar modulation ability (6.9%). This development represents a breakthrough for applications to smart windows.

Vanadium dioxide is a key material for thermochromic smart windows that can respond to environmental temperature and modulate near infrared irradiation by changing from a transparent state at low temperature to a more reflective state at high temperature, while maintaining visible transmittance. VO2 thermochromism is commonly used in films on glass that function as smart windows. Flexible VO2 nanocomposite foils are able to combine the intrinsic properties of VO2 nanoparticles with the added functionalities contributed by nanoscale and interface effects, such as increased visible transparency and infrared modulation ability. These foils are promising for applications in construction and automotive glasses to increase energy efficiency. However, VO2 nanoparticles may be unstable, and they are difficult to prepare in stable dispersive suspensions. In this paper, we report a novel all-solution process that can be used to prepare transparent, stable and flexible VO2-based composite films. These films exhibit UV-shielding properties and an excellent temperature-responsive thermochromism in the near infrared region. A typical film has a solar modulation efficiency of 13.6%, which is the highest value for VO2 thermochromic films with comparable visible transmittance. Coating the VO2 nanoparticles with a thin SiO2 shell significantly improved their anti-oxidation and anti-acid abilities. This result represents an important breakthrough in VO2 thermochromism, and it may have applications for near infrared modulation of glass used in construction or cars.

In this paper, uniform 1D VO2 (A) nanostructures with controllable morphologies were prepared via an easy one-step hydrothermal method for the first time. Aspect ratios are tunable from 10:1 to 1000:1 by changing the synthesis parameters such as the concentration of vanadium source and the reaction time. The mechanism of morphology evolution was investigated and discussed based on the nucleation and growth process of VO2 (A) particles. Electrochemical analyses of VO2 (A) nanostructures were performed, and the results showed a capacity of 277 mAh g−1 for a Li-ion battery using these nanostructures as cathode materials. This shows a significant improvement compared with other vanadium oxides such as VO2 (B) (approximately 180 mAh g−1) and V2O5 (approximately 230 mAh g−1). Unfortunately, the VO2 (A) nanostructures exhibit high initial irreversible loss due to the formation of an intermediate layer after electrochemical reactions.

A simple, low-cost hydrothermal method was developed to synthesize irregular-and rod-shaped lutetium disilicate (Lu2Si2O7) powders with sizes ranging from 71 to 340 nm. The synthesis temperature was 260 °C, which is nearly 1300 °C lower than that required for the solid-state reaction. The results indicated that both the hydrothermal temperature and pH values had great influences on the composition, crystalline phase and morphology of the powders. The formation mechanism, basic thermophysical properties, stability and anticorrosion properties of the Lu2Si2O7 powders were also investigated. The obtained powders possessed low thermal conductivity, a suitable thermal expansion coefficient (3.92–5.17×10−6 K−1) with the silicon-based substrate and excellent thermal and structural stability. During hot corrosion testing, the surfaces of the samples appeared to react with the water and molten salt vapors, but no serious failure occurred.Graphical abstractAn image for the as-prepared Lu2Si2O7 powders (left) and XRD pattern (right) (inset shows the SEM graph of powders).Highlights► We synthesized Lu2Si2O7 powders via a hydrothermal process at 260 °C. ► Crystalline phase and morphology of the powders changed with experimental parameter. ► Hot corrosion was determined in an airflow environment containing alkaline vapor.

Nanoscaled SnO2 with different morphologies has been synthesized via a simple hydrothermal process at 180 °C using polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate (SDS), cetyl trimethyl ammonium bromide (CTAB) or tetrapropyl ammonium bromide (TPAB) as surfactant. All the prepared SnO2 are of a tetragonal crystal structure. Nanocubes, nanorods, nanosheets, nanobelts and nanoparticles were prepared when changing the type and dosage of organic surfactants. It is shown that anionic surfactant (SDS) and cationic surfactant (CTAB or TPAB) at their suitable addition amounts can largely influence the morphologies of SnO2 nanocrystals. The effect is significantly dependent on the solvent types: water or ethanol. The non-ionic surfactant (PVP) can also change the morphologies like SDS but the impacts are less obvious. The effect of surfactants on the shape and size of SnO2 nanoparticles was discussed in detail. The particle growth mechanism is described based on the electrostatic interactions and Van der Waals’ forces.Graphical abstractSnO2 nanocrystals with controllable morphologies were prepared via a hydrothermal method with surfactants.Highlights► SnO2 nanocrystals were prepared via a hydrothermal method with surfactants. ► SnO2 morphologies changed with the type and the dosage of surfactants. ► The effect of surfactants on the growth of crystal planes was studied. ► The controlling mechanisms of surfactants on SnO2 morphologies were discussed.

Progress in the development of energy-efficient coatings on glass has led to the study of smart glass with special functional coatings that can regulate solar energy in response to an external stimulus. Thermochromic smart windows are considered attractive because they are visibly transparent and can intelligently control the amount of solar heat (mainly in the near-infrared region) in response to changes in ambient temperature. Discovered over 50 years ago, VO2 is the most promising thermochromic material; however, related materials have not been commercialized because of problems related to cost-efficient preparation, stability and performance. To date, gas-phase deposition methods, such as sputtering and chemical vapor deposition, are the most common methods for the fabrication of VO2 films, but these methods are still dependent on innovative technologies to meet the requirements of practical applications and are excluded from the topic of the current paper. This paper reviews the state-of-the-art solution processes used to prepare VO2 films, with a special emphasis on polymer-assisted deposition methods. The VO2 films prepared by these methods show controllable morphology and thickness and complex optical properties compared with those prepared by gas-phase methods. In fact, single-layered films exhibit the highest integrated visible transparency (43%) and solar-energy modulation ability (14%). These studies suggest that chemical preparation is inexpensive, easy to scale up, and best suited for the practical applications of the fabricated materials.Graphical abstractVO2 films with the Mott phase transition show unique properties including adsorption of ultra-violet light, visible transparency and temperature-responsive modulation ability to near-infrared light, and are key materials for energy-efficient smart windows of the next generation. This review discusses the state-of the art of solution processing of VO2 films.Highlights► Thermochromic VO2 is a promising material for energy-saving smart windows. ► Visible transparency and solar energy modulation ability limit application. ► Solution-based process increases the performance and lowers the cost. ► A series of concepts for the improvement of performance are reviewed.

Nanoporous thermochromic VO2 films with low optical constants and tunable thicknesses have been prepared by polymer-assisted deposition. The film porosity and thickness change the interference relationship of light reflected from the film−substrate and the air−film interfaces, strongly influencing the optical properties of these VO2 films. Our optimized single-layered VO2 films exhibit high integrated luminous transmittance (Tlum,l = 43.3%, Tlum,h = 39.9%) and solar modulation (ΔTsol = 14.1%, from Tsol,l = 42.9% to Tsol,h = 28.8%), which are comparable to those of five-layered TiO2/VO2/TiO2/VO2/TiO2 films (Tlum,l = 45%, Tlum,h = 42% and ΔTsol = 12%, from Tsol,l = 52% to Tsol,h = 40%, from Phys. Status Solidi A2009, 206, 2155−2160.). Optical calculations suggest that the performance could be further improved by increasing the porosity.Keywords (keywords): optical property; porosity; thermochromic property; vanadium dioxide

A novel solution deposition process has been developed to prepare thin crystalline ZrO2 layers on particle surfaces. The thickness and morphology of the ZrO2 layers can be controlled by using surfactants under different reaction conditions. A needle-shaped monoclinic ZrO2 array was formed by a multi-step deposition process with surfactants. Hollow ZrO2 capsules that were obtained by dissolving the nanoparticle cores exhibited obvious photocatalytic properties for the degradation of Rhodamine B. This is a general process that can form crystalline layers coated on matrix core particles in solution.

Free-standing La2Zr2O7 coatings were obtained by plasma spraying, using an amorphous La-O-Zr precursor as the feedstock. The La-O-Zr precursor powder was prepared by coprecipitation. During thermal spraying, the formation of coatings can be regarded as a joint process of melting-solidification, thermal decomposition, and crystallization. The time required for crystal growth was significantly shortened during spraying. Consequently, the average grain size of coatings was approximately 200 nm, with a narrow distribution (100-500 nm). Coatings prepared by this method show better thermophysical properties than those prepared with crystalline La2Zr2O7 powder as the feedstock. The thermal conductivity of the as-sprayed coating was approximately 0.36-0.47 W/m K and the average coefficient of thermal expansion (CTE) is 11.1 × 10−6/K.

A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb2Si2O7 and Yb2SiO5) nanoparticles at 200 °C. This is nearly 1000 °C lower than that for the typical sol−gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation.

Rutile vanadium dioxide (VO2 (R)) hollow spheres with nanorods aggregating on their surface were successfully synthesized through a novel surfactant-assisted hydrothermal process in which polyvinylpyrrolidone (PVP) served as a soft template. The crystal structure and morphology were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Hollow spheres show an obvious Mott phase transition at 63.0 (heating semicycle) and 53.1 °C (cooling semicycle). Reaction conditions influencing the synthesis of these VO2 hollow spherical structures (i.e., reaction temperature, time and PVP addition amount) were investigated. Furthermore, a mechanism for the growth of the VO2 hollow spheres is proposed.

In this article, thermochromic VO2 films were deposited on fused quartz and rutile TiO2-buffered fused quartz substrates via a solution-phase process. The incorporation of a TiO2 buffer layer endures an enhanced oxidization durability of VO2 films under an environment with high oxygen partial pressures. Oxidization in furnace during a cooling stage and rapid thermal oxidization (RTO) treatments were employed to investigate the evolution of microstructures and compositions of the films in the gradual oxidization processes. Oxidization treatments transformed VO2 into V2O5 for films grown on fused quartz substrates, whereas the oxidation process was significantly hindered for films prepared on a TiO2 buffer layer, especially around the VO2/TiO2 interface. The phenomenon is first reported in this article and is important for practical applications.

Spindlelike mesoporous anatase titania particles were directly synthesized at a low temperature (95 °C) by using an aqueous peroxotitanium solution with polyacrylamide (PAM). The mesoporous titania had a BET-specific surface area of 89.6 m2 g−1 and showed high crystallinity, thermal stability, and good photocatalytic activity in the degradation of rhodamine B. PAM, as an additive, was confirmed to be crucial in the evolution of the specific structure, morphology, and crystalline phase, and a possible formation mechanism was suggested.

This study was conducted to clarify the effects of soluble polymers on the nucleation and growth of ZnO films in solution. The role of polymers is twofold. First, the indiscriminating adsorption of Zn(II) ions onto polymer surfaces, which leads to site-specific supersaturation with respect to the nucleation of ZnO, and secondarily, the charged polymer may change the surface charges of ZnO and alter the precipitation process. The former mainly occurs in the beginning of reactions, and the latter operates predominantly after the formation of ZnO nuclei. In addition, this research demonstrates the possibility of synthesizing inorganic/organic composites with special morphologies by regulating the dissolution–recrystallization chemistry that is regulated by polymer modification, and supports a novel process to optimize the structures.

This work confirmed experimentally that the microstructure (grain boundaries, grain sizes, and size distributions) of VO2 films has significant effects on the features of the semiconductor−metal (S−M) transition. This feature enables us to wisely regulate the parameters of the phase transition, which is of great importance in achieving practical applications. Thermochromic VO2 films with various optical properties and phase transition parameters (for example: hysteresis widths ranging from 12 to 50 °C) have been synthesized on fused silica substrates via a simple solution process with inorganic precursors and polyvinylpyrrolidone (PVP). The widths and slopes of the hysteresis loops (i.e., the temperature sensitivity of the transition) can be regulated by controlling grain sizes and grain boundary conditions, which are believed to dominate the generation of the elementary hysteresis loop of each grain and the propagation of the S−M transition, respectively. A film consisting of qusai-isolated small particles shows a wide hysteresis loop due to the large interfacial energies and the lack of defects for nucleating. Besides, grain boundaries can decrease the interfacial energies and favor the phase propagation. In addition, particle sizes seem to influence the visible transmittances of these films effectively without deterioration of the infrared regulation ability. This experimental phenomenon is assigned to the blue shift of absorption edges (at around 500 nm) accompanying decreases in particle size.

This paper describes a solution-phase synthesis of high-quality vanadium dioxide thermochromic thin films. The films obtained showed excellent visible transparency and a large change in transmittance at near-infrared (NIR) wavelengths before and after the metal−insulator phase transition (MIPT). For a 59 nm thick single-layer VO2 thin film, the integral values of visible transmittance (Tint) for metallic (M) and semiconductive (S) states were 54.1% and 49.1%, respectively, while the NIR switching efficiencies (ΔT) were as high as 50% at 2000 nm. Thinner films can provide much higher transmittance of visible light, but they suffer from an attenuation of the switching efficiency in the near-infrared region. By varying the film thickness, ultrahigh Tint values of 75.2% and 75.7% for the M and S states, respectively, were obtained, while the ΔT at 2000 nm remained high. These results represent the best data for VO2 to date. Thicker films in an optimized range can give enhanced NIR switching efficiencies and excellent NIR blocking abilities; in a particularly impressive experiment, one film provided near-zero NIR transmittance in the switched state. The thickness-dependent performance suggests that VO2 will be of great use in the objective-specific applications. The reflectance and emissivity at the wavelength range of 2.5−25 μm before and after the MIPT were dependent on the film thickness; large contrasts were observed for relatively thick films. This work also showed that the MIPT temperature can be reduced simply by selecting the annealing temperature that induces local nonstoichiometry; a MIPT temperature as low as 42.7 °C was obtained by annealing the film at 440 °C. These properties (the high visible transmittance, the large change in infrared transmittance, and the near room-temperature MIPT) suggest that the current method is a landmark in the development of this interesting material toward applications in energy-saving smart windows.

This article describes a novel and simple route to preparing VO2 thermochromic films by using a VOCl2 solution with poly(vinylpyrrolidone) (PVP). X-ray diffraction and Raman spectra showed that the VO2 films deposited with PVP consisted of a nearly pure monoclinic/rutile (M/R) phase. Conversely, films prepared without PVP contained obviously impure crystalline phases. The as-prepared films with PVP showed excellent optical properties compared to those prepared by common gas-phase methods: an integral visible transmittance of 54.5% and an IR reduction (change in transmittance) of 41.5% at 2000 nm. The phase-transition temperatures were adjusted from 69 to 54 °C by tungsten doping. Equipment analyses revealed that PVP plays two roles in the film formation. First, it fundamentally acts as a film-forming promoter to improve physical gelation via interactions among oppositely charged carbonyl groups and amine groups of the polymer. Second, the negatively charged carbonyl groups can interact with VO2+ to form a uniform mixed-gel film after solvent evaporation. Thus, the addition of PVP can stabilize the solution and improve the as-prepared film quality and phase purity. The current study suggests that the process has promise in applications of smart windows.Keywords: crystalline phase; polymer; smart window; thermochromic property; thin film; vanadium dioxide

Nano-scaled lanthanum zirconate powder prepared by co-precipitation–calcination method was plasma-sprayed into a thick coating on an alloy substrate. We investigated the thermophysical properties of the free-standing coating, including thermal conductivity and thermal expansion coefficients (TECs). Minimum value of the thermal conductivity (at 900 °C) of the coating was about 0.73 W m−1 K−1, and the average TEC in the measurement range was about 9.45 × 10−6 K−1. Although the TEC value was similar to that of the bulk material, the change tendency versus temperature was different. After annealing at 1300 or 1400 °C for 50 h, we found that the heat insulation performance of the coating decreased with the heat treatment temperature, while the hardness and fracture toughness increased. A peak of sudden decrease in TEC value can be observed in the curve, and with increasing temperature, the peak shifted to high-temperature direction.

Zirconia-precursor-coated hematite particles were prepared by hydrolysis of zirconium sulfate in aqueous solution. The as-prepared zirconia-precursor shell was amorphous with a thickness of about several ∼30 nm that can be controllably achieved by varying the processing parameters and had a composition of Zr2(OH)6SO4, which crystallized to tetragonal ZrO2 after annealing at 700 °C. The focus of this work is to investigate in detail the process and to understand the key issues for surface coating in solution. The thermodynamic analysis on hydrolysis of zirconium sulfate was conducted, and a “surface-deposition region” for zirconia coating was suggested in this work. Furthermore, the kinetic study of the process was also described. The hydrolysis could be considered as a pseudo-second-order reaction at 50 °C, and the rate constant was calculated to be 0.61 L mol−1 s−1. The hydrolysis mechanism of zirconium salt was also interpreted from the viewpoint of structural chemistry. The influence of the surfactants on the coating process was also discussed.

A novel general method for coating particles with a complex oxide was described. Zirconia precursor and silica layers with careful control of film thickness were coated separately onto hematite particles in corresponding solutions. A zircon shell was subsequently obtained by heat treatment at 800 °C for 3 h using LiF as a mineralizer. The as-prepared zircon-occluded hematite pigment gave a pink color to the glazed sample after annealing at 1120 °C. The current research suggests that various chromophoric particles can be encapsulated with zircon to prepare ceramic pigments for high-temperature use.

We report for the first time the formation of spindle-type, monodispersed anatase nanorods from a peroxotitanate solution without the use of organics (such as surfactants). The formation process is highly dependent upon soaking time, solution pH, and concentration, undergoing both morphology and phase transformation during growth. We found that the mechanism of formation is similar to that of a gel−sol process: the initial amorphous gel is converted to anatase titania rods using ammonia as a shape controller. Both previous and current studies on the synthesis of TiO 2 from peroxotitanate solution show that, under appropriate conditions, the peroxotitanate solution can be used to produce large quantities of TiO 2 nanoparticles of controlled polymorph type, morphology, and size.

ZnO powders were synthesized in the presence of water-soluble polymers. These polymers have effects on the nucleation and growth of ZnO crystals in solution, resulting in difference in crystalline morphologies. The role of polymers is 2-fold: first, indiscriminating adsorption of Zn(II) ions onto the polymer surfaces, which leads to the site-specific supersaturation with respect to the nucleation of ZnO, and secondarily, morphological development by interactions of zinc species with polymers and their hydrolyzed products. The incorporation of polymers into crystals was also confirmed experimentally. After annealing, mesopores were present in powders. This study shows the possibility to synthesize inorganic/organic composites with special morphologies, and suggests a novel process to optimize structures for the achievement of advanced functions.

Yttria-stabilized zirconia (YSZ) has received great attention as a thermal barrier coating (TBC) material for its excellent thermal and mechanical properties. However, the grain growth of YSZ, particularly under temperatures higher than 1200 °C, limits its further applications to a great extent. In our present study, to develop better understanding of the aforementioned phenomenon and explore effective methods to conquer this challenge, TBCs using traditional and La2O3-modified YSZ powders were deposited by atmospheric plasma spraying and their microstructures were investigated. The results show that the La2O3 addition can effectively alleviate the grain growth of coatings under high temperatures.

This paper reports the effects of the aspect ratio of zinc oxide (ZnO) nanowires on the performance of ZnO-nanowire-based dye-sensitized solar cells (DSSCs). ZnO nanowire-structured photoanodes can improve the efficiency of the electron collection of DSSCs, but their performances significantly depend on the aspect ratio of component nanowires and their array structures. The aspect ratio of nanowires has been successfully regulated by controlling the supersaturation degree of solutions, that is, simply by changing the molar ratio of Zn(II)/NH3. A highly oriented, single crystalline, long ZnO nanowire with a fine aligning structure was obtained with an aspect ratio of about 100–120 (diameter: 120–150 nm, length: 14 µm). The main crystalline phase measured by X-ray diffraction and Raman scattering was proven to be wurtzite-type ZnO, whereas the appearance of another phase was also detected. The films show a transmittance of about 60% in the visible light region and optical band gaps at around 3.2 eV. An overall conversion efficiency of about 1.7% was obtained, which is almost three times of that we reported previously. The present research points out a possible way to improve ZnO-based DSSCs by engineering a nanostructured electrode.