Conduction Band Edge Of TiO2 Research Articles

Investigating the Role of I2SCN− on the Fermi Level of Electrolyte for Dye-Sensitized Solar Cells

We investigated the electrochemical effect of the formation of a halogen-pseudohalogen complex ion, I2SCN− (diiodothiocyanate), on the Fermi level of the conventional I−/I3−-based electrolyte when thiocyanate was added as an additive into the electrolyte of dye-sensitized solar cells. It was found that the formation of I2SCN− induced a negative shift in the Fermi level of the electrolyte (positive in potential scale), resulting in a net enhancement of the open circuit voltage (Voc), up to ca. 30mV, for the cells with 1-ethyl-3-methylimidazolium thiocyanate as additive. A significant negative shift of the conduction band edge of TiO2, up to ca. 115meV, upon adsorption of guanidinium cation on TiO2 surface was almost counterbalanced by the retardation of charge recombination at the TiO2|electrolyte interface due to the adsorbed cation itself and therefore, the net enhancement of the Voc was mostly associated with the formation of the new redox level represented by (I−, SCN−)/I2SCN− with a standard electrochemical potential more positive than that of I−/I3−.

Photophysics of a ruthenium 4H-imidazole panchromatic dye in interaction with titanium dioxide.

The photophysics of bis(4,4'-di-tert-butyl-2,2'-bipyridine-κ(2)N,N')[2-(4-carboxyphenyl)-4,5-bis(p-tolylimino-κN)imidazolato]ruthenium(II) hexafluorophosphate is investigated, both in solution and attached to a nanocrystalline TiO2 film. The studied substitution pattern of the 4H-imidazole ligand is observed to block a photoinduced structural reorganization pathway within the 4H-imidazole ligand that has been previously investigated. Protonation at the 4H-imidazole ring decreases the excited-state lifetime in solution. When the unprotonated dye is anchored to TiO2, photoinduced electron injection occurs from thermally nonrelaxed triplet metal-to-ligand charge transfer ((3)MLCT) states with a characteristic time constant of 0.5 ps and an injection efficiency of roughly 25%. Electron injection from the subsequently populated thermalized (3)MLCT state of the dye does not take place. The energy of this state seems to be lower than the conduction band edge of TiO2.

Microscopic dynamics research on the "mature" process of dye-sensitized solar cells after injection of highly concentrated electrolyte.

After injection of electrolyte, the internal three-dimensional solid-liquid penetration system of dye-sensitized solar cells (DSCs) can take a period of time to reach "mature" state. This paper studies the changes of microscopic processes of DSCs including TiO2 energy-level movement, localized state distribution, charge accumulation, electron transport, and recombination dynamics, from the beginning of electrolyte injection to the time of reached mature state. The results show that the microscopic dynamics process of DSCs exhibited a time-dependent behavior and achieved maturity ∼12 h after injecting the electrolyte into DSCs. Within 0-12 h, several results were observed: (1) the conduction band edge of TiO2 moved slightly toward negative potential direction; (2) the localized states in the band gap of TiO2 was reduced according to the same distribution law; (3) the transport resistance in TiO2 film increased, and electron transport time was prolonged as the time of maturity went on, which indicated that the electron transport process is impeded gradually; (4) the recombination resistance at the TiO2/electrolyte (EL) interface increases, and electron lifetime gradually extends, therefore, the recombination process is continuously suppressed. Furthermore, results suggest that the parameters of EL/Pt-transparent conductive oxide (TCO) interface including the interfacial capacitance, electron-transfer resistance, and transfer time constant would change with time of maturity, indicating that the EL/Pt-TCO interface is a potential factor affecting the mature process of DSCs.

Can 2-pyrone derivative act as an effective π-linker for dye-sensitized solar cells: a theoretical study?

Thiophene and derivatives have been broadly used in metal-free organic dyes as π-bridge in the past 10 years. However, the relatively sharp and narrow visible absorption bands of these organic dyes not only severely attenuated the light capture capability but also restrict the efficiency. In this contribution, to design efficient sensitizers for dye-sensitized solar cells, a series of triphenylamine (TPA) dyes with 2-pyrone as the π-bridge are investigated using the density functional theory and time-dependent density functional theory approaches. The results show that the designed dyes have smaller gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the absorption bands are greatly bathochromic-shifted by at least 39 nm and the light-harvesting efficiencies are improved compared to the experimentally efficient sensitizer T with thiophene as the π-bridge. The calculated values of free energy change ΔG inject for all the designed dyes are very negative, which favors electron injection from the excited-state dye to the TiO2 conduction band edge. Our simulations show that the sensitizers studied here are strongly adsorbed to the TiO2 cluster. During light excitation, electrons are transferred from the TPA group through the π-spacer to the surface-bound cyanoacrylate, facilitating electron injection to the TiO2 nanoclusters. Our calculations indicate that the newly designed dyes will be promising candidates for the future solar cell applications.

Effects of polymer chemistry on polymer-electrolyte dye sensitized solar cell performance: A theoretical and experimental investigation

The effects of polymer chemistry on interfacial properties and overall performance in polymer-electrolyte dye sensitized solar cells (DSSCs) are investigated theoretically and experimentally. Specifically, polymer electrolytes based on poly(2-hydroxyethyl methacrylate) (PHEMA), poly(glycidyl methacrylate) (PGMA), and poly(4-vinylpyridine) (P4VP) are considered. These polymers are grown directly within the mesoporous TiO2 photoanode via a single step polymerization and coating using initiated chemical vapor deposition (iCVD) to maximize pore filling. The experimental study coupled with a 1-D first-principles macroscopic DSSC mathematical model provides insight into the cell interfacial processes and overall performance. Parameter estimation using the macroscopic model indicates that the pendant groups on the polymers strongly affect the conduction band position of TiO2, the back electron transfer at the photoanode-electrolyte interface, and the exchange current density at the platinum cathode. The estimated difference between the TiO2 conduction band edge and the redox potential of the electrolyte are 0.87, 0.99 and 1.06 eV for P4VP, PGMA, and PHEMA, respectively. Estimated recombination rate constants for P4VP and PGMA are respectively 54% and 19% lower than that of PHEMA. This study indicates that by varying polymer electrolyte chemistry, DSSC characteristics including open-circuit voltage, short-circuit current density, and fill factor can be tuned.

Efficiency enhancement via tailoring energy level alignment induced by vanadium ion doping in organic/inorganic hybrid solar cells

Photovoltaic performances are critically dependent on efficient photoexcited charge carrier generation. Vanadium ions are introduced into titanium dioxide (TiO2) as a photocatalyst to tailor the energy level alignment of TiO2 and the conjugated polymer poly(3-hexylthiophene) (P3HT). Incorporation of vanadium ions into TiO2 yields a remarkable decrease of the energy offset between the conduction band edge of TiO2 and the lowest unoccupied molecular orbital of P3HT. The reduction of the ‘excess’ energy offset leads to a faster electron transfer at the interface of the bulk heterojunction with the lifetime decreasing from 30.2 to 19.7 ps, thus giving rise to a notable enhancement of the photovoltaic performance. That is, a power conversion efficiency of 3.01% for the vanadium-doped TiO2/P3HT solar cell at 5.0 wt% vanadium-doping is obtained as compared to 2.00% for pure TiO2.

The origin of efficiency enhancement of inorganic/organic Hybrid solar Cells by robust samarium phosphate nanophosphors

An effective energy level regulation of acceptor by doping samarium phosphate nanophosphors (SmPO4 NPs) was reported for inorganic/organic hybrid solar cell applications. SmPO4 NPs doped TiO2/P3HT bulk heterojunction (BHJ) solar cell shows an enhanced power conversion efficiency of approaching 3% as compared with that of its counterpart without SmPO4 NPs (1.98%). The underlying photophysical mechanism was probed by applying femtosecond transient absorption spectroscopy and the results show that the efficiency enhancement was ascribed to the improved hot electron, less energetic electron, hole transports at the interface of BHJ apart from down-conversion photoluminescence of SmPO4 NPs. It has been evidenced that the hot electron transfer life time was shortened by more than 40% (i.e., from τhot-e=30.2 to 17.9ps) than pure TiO2 acceptor while the hole transfer lifetime was boosted by almost 20% (i.e., from 6.92 to 5.58ns). Such charge carrier improvements stem from the efficient energy level regulations by SmPO4 NPs. In detail, the conduction band (CB) edge of TiO2 has been elevated by 0.57eV while the valence band (VB) edge has been elevated by 0.32eV, thus not only narrowing down the energy offset between CB energy levels of acceptor TiO2 and donor P3HT, but also meanwhile enlarging the band gap of TiO2 itself that permits to inhibit electron-hole recombination within TiO2. This work demonstrates that samarium ions can efficiently facilitate exciton generation, dissociation and charge transport and have an important role in enhancing photovoltaic performance.

Efficiency enhancement of dye-sensitized solar cells by interface modification between photoanode and electrolyte.

A nanoporous TiO2 layer on a transparent electrode was modified with an aqueous lithium hydroxide solution by a simple dipping process, and effects of the modified electrode on the photovoltaic properties of dye-sensitized solar cells were investigated. The modification led to a considerable improvement of 23.6% in power conversion efficiency due to an increase in both open circuit voltage and fill factor. From the measurements of the electronic band structure, electrochemical impedance spectra and incident photon-to-current conversion efficiency, it was revealed that the modification by LiOH formed a surface dipole on the TiO2 electrode, leading to a negative shift of conduction band edge of TiO2.

Synthesis, photophysical and electrochemical properties of two novel carbazole-based dye molecules

Two carbazole-based dye molecules: 3-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-2-cyano-acylic acid (D3) and 3-[5-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-thiophen-2-yl]-2-cyan-acylic acid (D4) were synthesized by an approach from carbazole derivate using Vilsmeier-Haack, Suzuki cross-coupling and Knoevenagel reactions. Their physical and electrochemical properties were investigated. D3 and D4 exhibit different optical properties, such as UV absorption, photoluminescence, fluorescence quantum yield and fluorescence lifetime in different solvents. Compared with D3 without a thiophene unit, the maximum absorption wavelength of D4 red-shift obviously and its fluorescence intensity is also enhanced. A shift of the EHOMO and ELUMO is observed for D3 (EHOMO=2.06V, ELUMO=−1.39V vs. NHE) and D4 (EHOMO=1.73V, ELUMO=−1.33V vs. NHE). D3 and D4 can be used as dyes for dye-sensitized solar cells (DSSCs) with TiO2 nanomaterial because their EHOMO are lower than the conduction band edge of TiO2 [−0.5V (vs. NHE)] and their ELUMO are higher than the I3−/I− redox potential [0.42V (vs. NHE)].

A Ruthenium‐Based Light‐Harvesting Antenna Bearing an Anthracene Moiety in Dye‐Sensitized Solar Cells

AbstractA heteroleptic ruthenium sensitizer (DV56) bearing a terpyridine ligand with an appended phenylanthracene moiety was synthesized and extensively characterized. The physicochemical properties of the light‐harvesting antenna were studied in solution and on sensitized TiO2 thin film electrodes using a variety of spectroscopic and photoelectrochemical techniques. Contact angle measurements suggest that the DV56‐sensitized TiO2 films are hydrophilic. Raman measurements indicate chemisorption of the dye on the semiconducting surface. Electrochemical studies of the dye show that its first oxidation potential lies well below the I−/I3− redox potential, allowing easy regeneration. Moreover, its excited state oxidation potential lies above the TiO2 conduction band edge, permitting efficient electron injection from the photosensitizer into the semiconductor. I−/I3−‐based liquid redox electrolyte dye‐sensitized solar cells incorporating DV56‐sensitized TiO2 photoelectrodes afford an overall power conversion efficiency of 3.75 %.

Theoretical insight into electronic and photoelectrochemical properties of orcein dyes relevant to dye-sensitized solar cells

Electronic and photoelectrochemical properties of the natural dyes a-, b-, and c-orceins, related to the performance of dye-sensitized solar cells, were studied by density functional theory (DFT) and time-dependent TDDFT at the B3LYP/6-31?G(d) level. The integral equation formalism-polarizable continuum model (IE- FPCM) was employed for solvation effect. The computational results show that all eight orcein dyes can be suggested for use as a photosensitizer in DSSC due to their matching electronic energy LUMO and HOMO levels for the conduction band edge of TiO2 and the oxidation potential of I - /I3 - electrolyte, respectively. The b-AOI and c-AIO possess the best computed parameters related to photochemical properties such as excited state oxidation potential, electron injection force, and photoinduced elec- tron transfer and also open-circuit voltage among the other

Synthesis and characterization of carbon nanotubes-treated Ag@TiO2 core–shell nanocomposites with highly enhanced photocatalytic performance

The monodispersed, uniform Ag@TiO2 core–shell nanoparticles were successfully synthesized using Ag nanoparticles as colloid seeds and tetrabutyl titanate (TBOT) as Ti source through the simple solvothermal process. The acid vapor treated multi-walled carbon nanotubes (CNTs) were introduced into Ag@TiO2 core–shell system to obtain CNTs-loaded Ag@TiO2 nanocomposites (CNTs-Ag@TiO2) through a simple dipping method. Characterization of the composites was performed using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and High-resolution TEM (HRTEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and the X-ray photoelectron spectroscopy (XPS). Photocatalytic property of CNTs-Ag@TiO2 nanocomposites was investigated by photodegradation methylene blue (MB) solution under Xenon arc lamp and compared with Ag@TiO2, TiO2 and CNTs-TiO2 nanoparticles. The result showed that the photocatalysis property of CNTs-Ag@TiO2 nanocomposites was higher than other comparative particles. The presence of CNTs in the Ag@TiO2 nanocomposites could enhance the photocatalytic property owing to CNTs were good electron acceptors, can accept the excited electrons photo-initiated in the TiO2 particles and the Fermi level of the Ag is situated close to the conduction band edge of TiO2. Thus the electrons excited into the conduction band of TiO2 by UV–visible light irradiation are transferred to the surface of CNTs and Ag core easily. Therefore, recombination time of the electron–hole pair was prolonged, which was the key of enhance the photocatalytic activity.

Femtosecond Transient Absorption Study of Supramolecularly Assembled Metal Tetrapyrrole–TiO2 Thin Films

Photoexcited electron injection and back electron transfer dynamics of metal tetrapyrrole bound to TiO2 nanoparticle surfaces via the metal–ligand axial coordination approach have been investigated using femtosecond pump–probe transient spectroscopic technique. The employed metal tetrapyrroles include zinc and magnesium metalated meso-tetraarylporphyrins having halogen substituents on the peripheral aryl groups, perfluorinated zinc phthalocyanine derivatives, and zinc naphthalocyanine. The employed metal tetrapyrroles covered absorption at different portions of the visible and near-IR region of the spectrum with excited-state reduction potentials ranging between −0.61 eV and −1.34 V, that is, having energy higher than the TiO2 conduction band edge (−0.57 V vs NHE). Two linkers, pyridine and phenylimidazole, have been employed to visualize electronic coupling between the dye and metal oxide surface for optimal electron injection and back electron transfer dynamics. In agreement with the previously reported photocurrent generation of dye-sensitized solar cells constructed using this self-assembly approach (J. Am. Chem. Soc. 2009, 131, 14646), spectral evidence for electron injection from the excited metal tetrapyrrole to the TiO2 nanoparticle in the form of a tetrapyrrole radical cation has been obtained. The time profile of the π-cation radical of tetrapyrroles revealed the occurrence of ultrafast electron injection (time constant = 470–700 fs), while the back electron transfer processes were found to be complicated due to the intricate environment of the metallotetrapyrrole–TiO2 interface.

Influence of conjugated π-linker in D–D–π–A indoline dyes: towards long-term stable and efficient dye-sensitized solar cells with high photovoltage

The judicious choice of conjugated π-linkers is a critical strategy towards the energy-level engineering of donor–π–acceptor (D–π–A) sensitizers. Given that the vinyl bond on π-bridge thiophene segment can deteriorate its intrinsic photo-stability, we systematically study three D–D–π–A indoline dyes C-CA, WBS-1T and WBS-1F with different conjugated π-linkers (vinylthiophene, thiophene and furan) for high efficiency, long-term stable dye-sensitized solar cells (DSSCs). Compared with the vinylthiophene unit in C-CA, the conjugated π-linker of the thiophene or furan group in WBS-1T and WBS-1F can improve the solar cell performance with a great enhancement in the open-circuit photovoltage (VOC). As an overall result of the upshift of the TiO2 conduction band (CB) edge and the slow charge recombination, the VOC values are in the order WBS-1F (779 mV) > WBS-1T (756 mV) > C-CA (670 mV). Moreover, the CB edge shift of TiO2 is the major contribution to the large difference in VOC, accounting for 80% of the enhancement. Both the stepped light-induced transient measurements (SLIT) and the molecular dipole simulation are accounted for well by the observed superior photovoltage upon removal of the vinyl group in the conjugated π-linker. The higher molecular dipole moments can bring forth a more effective charge separation between donor and acceptor units, resulting in a remarkable increase in VOC. Using a liquid electrolyte, WBS-1F shows an impressively high efficiency of 9.49% with a high photovoltage of 779 mV. Its efficiency reaches 8.03% with ionic-liquid electrolyte while it reduces to 7.60% after a 1000 h aging test. Our work has shown that for D–π–A organic dyes, the vinyl unit in the conjugated π-linker is detrimental to the molecular dipole moment, the upshift of TiO2 CB edge, and the suppression of charge recombination, as well as the photo-stability.

Post-treatment on dye-sensitized solar cells with TiCl4 and Nb2O5

Post-treatment of TiCl4 improves the overall conversion efficiency of dye-sensitized solar cells by enhancing the photocurrent (JSC) rather than the photovoltage (VOC), owing to an 80 mV downward shift in the TiO2 conduction band edge potential. Further treatment with niobium isopropoxide forms a Nb2O5 barrier layer that induces an upward shift in the Fermi energy and decreases the recombination rate, resulting in larger VOC. Quite intriguingly, the incident photon to current conversion efficiency results show that this second treatment also enhances JSC. Thus, the resulting electrode shows an improved conversion efficiency (by ca. 52%) over that of the non-treated electrode.

Ionic Liquid–Sulfolane Composite Electrolytes for High‐Performance and Stable Dye‐Sensitized Solar Cells

Ionic liquid electrolytes are prepared using sulfolane as a plasticizer for eutectic melts to realize highly stable and efficiently performing dye‐sensitized solar cells (DSCs) in hot climate conditions. Variations in the viscosity of the formulations with sulfolane content are measured and performance in DSCs is investigated using the ruthenium dye C106 as a sensitizer. A power conversion efficiency (PCE) of 8.2% is achieved under standard reporting conditions. Apart from lowering the viscosity, the addition of sulfolane induces a negative shift of the TiO2 conduction band edge. Strikingly the device performance increases to 8.4% at 50 °C due to higher short circuit photocurrent and fill factor, over‐compensating the loss in open circuit voltage with increasing temperature. The PCE increases also upon decreasing the light intensity of the solar simulator, reaching up to 9% at 50 mW cm−2. Devices based on these new electrolyte formulations show excellent stability during light soaking for 2320 h under full sunlight at 60 °C and also during a 1065 h long heat stress at 80 °C in the dark. A detailed investigation provides important information about the factors affecting the principal photovoltaic parameters during the aging process and the first results from a series of outdoor measurements are reported.

Electron Injection Dynamics from Photoexcited Porphyrin Dyes into SnO2and TiO2Nanoparticles

The photoexcited electron injection dynamics of free-base and metallo-derivatives of tris(pentafluorophenyl)porphyrins bound to TiO2 and SnO2 nanoparticle surfaces have been investigated using time-resolved terahertz spectroscopy (TRTS). The metallo-derivatives include Zn(II), Cu(II), Ni(II), and Pd(II). For the TiO2–porphyrin assemblies, electron injection from the photoexcited dye to the semiconductor occurs only when using the zinc derivative as the sensitizer because it is the only dye studied in this report with long-lived excited states higher in energy than the TiO2 conduction band edge. All of the dyes, however, have excited-state energies above the SnO2 conduction band edge, and the electron injection rates vary widely from 0.4 to 200 ps depending on the sensitizer. For the SnO2–porphyrin assemblies, electron injection is strongly influenced by competition with alternate deactivation routes that are accessible following Soret band excitation. These results offer thermodynamic and kinetic considerations for designing improved high-potential porphyrin photoanodes with applications to solar-powered water oxidation.

Efficient Dye‐Sensitized Solar Cells Using a Tetramethylthiourea Redox Mediator

An organic redox couple tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS(2+) ) is evaluated in dye-sensitized solar cells in conjunction with a series of indoline and ruthenium-based dyes. Of these, devices with indoline dye D205 show the best performance, with an optimized power conversion efficiency of 7.6 % under AM 1.5G 1 sun illumination. Charge collection and injection are highly efficient in all TMTU-based DSCs studied. Regeneration of indoline dyes is highly efficient, whereas regeneration of ruthenium dyes by TMTU is less efficient, accounting for their inferior performance. Impedance spectroscopy results reveal that using an optimized TMTU/TMFDS(2+) electrolyte solution, the TiO2 conduction band edge is 300-400 meV lower than when an optimized I3 (-) /I(-) electrolyte is used. The would-be loss in open-circuit voltage caused by the downward conduction band shift is mostly compensated by approximately the 200 meV lower redox level of the TMTU/TMFDS(2+) electrolyte and up to 1000 times slower recombination rates. This makes TMTU/TMFDS(2+) a promising redox couple in the development of highly efficient solar energy conversion devices.

Morphology and Interfacial Energetics Controls for Hierarchical Anatase/Rutile TiO2 Nanostructured Array for Efficient Photoelectrochemical Water Splitting

In this work, a three-dimensional (3D) hierarchical TiO2 nanostructured array is constructed on the basis of the considerations of morphology and interfacial energetics for photoelectrochemical water splitting. The photoelectrode is composed of a core-shell structure where the core portion is a rutile TiO2 nanodendrite (ND) array and the shell portion is rutile and anatase TiO2 nanoparticles (NPs) sequentially located on the surface. The TiO2 ND array provides a fast electron transport pathway due to its quasi-single-crystalline structure. The 3D configuration with NPs in the shell portion provides a larger surface area for more efficient photocharge separation without significantly sacrificing the electron collection efficiency. Moreover, anatase TiO2 NPs constructed on the surface of the ND/rutile TiO2 NP nanostructured array enhance charge separation and suppress charge recombination at the interfacial region due to the higher conduction band edge of anatase TiO2 compared to that of rutile TiO2. A photocurrent density and photoconversion efficiency of 2.08 mA cm(-2) at 1.23 V vs reversible hydrogen electrode (RHE) and 1.13% at 0.51 V vs RHE are, respectively, attained using the hierarchical TiO2 nanostructured array photoelectrochemical cell under illumination of AM 1.5G (100 mW cm(-2)).

Effect of thiourea incorporation in the electrolyte on the photovoltaic performance of the DSSC sensitized with pyridyl functionalized porphyrin

In this study, we investigate the effect of a thiourea containing electrolyte on the photovoltaic response of a dye sensitized solar cell (DSSC) that is based on an A3B-type meso substituted porphyrin (where A and B are methyl-benzoate and phenylethynyl-pyridine, as electron acceptor and anchoring groups, respectively). A significant increase in the short circuit photocurrent (Jsc) of the solar cell is observed (from 9.38mA/cm2 to 11.93mA/cm2), which is attributed to a positive shift of the TiO2 conduction band (CB) edge and to a decrease in the charge recombination rate. The short circuit photocurrent Jsc dependence on the illumination intensity Pin and its reduction in dark current confirm that the increased electron injection efficiency is due to the positive shift in the TiO2 CB edge and suppression of the back charge recombination of injected electrons. The charge recombination retardation has been attributed to chemisorbed thiourea cations on the TiO2 surface, as confirmed by UV–vis absorption spectra and XRD patterns of the pure and thiourea doped TiO2 films. Electrochemical impedance spectroscopy (EIS) results indicate that the chemisorbed on the TiO2 surface thiourea cations might passivate the surface recombination sites and enhance the electron lifetime in the nanostructured TiO2 film, resulting in a slight improvement of the open circuit voltage (Voc) of the solar cell, in spite of the positive shift of the thiourea containing electrolyte CB edge. The overall power conversion efficiency (PCE) of the DSSC based on thiourea containing electrolyte (E2) is 5.34%, which is higher than the corresponding DSSC without thiourea electrolyte (E1) (3.36%), under identical conditions.