Long-Term Activity of Thermoplastic Gel Electrolyte in a Photo-Electrochemical Assembly Involving Poly Bithiophene (PBTh) as Photoactive Working Electrode

Evidence for the long period of a sustainable function of a thermoplastic gel electrolyte (TPGE) consists of polyethylene glycol (PEG)/I2/I- in propylene carbonate (PC) was recorded. The studied photoactive assembly consists of PBTH/FTO/TPGE I2/I-/Platinized FTO. The study showed that the assembly regenerates the expected photoelectrochemical (PEC) quantities such as photocurrent, and other dielectric properties with infrequent use through an elapsed period of 18 months. The behavior of PBTh/occluded with CdS was mentored during this period and showed a similar result. PEC studies indicated the presence of p-p type hole accumulations interface, evident from the initial sharp rise in photocurrent. The change of open circuit potential (dVoc) indicates that the shortest electron lifetime is 100 ms. The behavioral outcome of the assemblies within the period of study refracts stability of the electrode and the long life cycle of the electrolyte.

Photoelectrochemical and Spectroscopic Studies of Colloidal Nano-Particles of Mixed TiO₂/V₂O₅Metal-Oxide Semiconductors

Due to its importance in hydrogen production during the photolysis process of aqueous suspensions process, mixed TiO2/V2O5 metal-oxide semiconductors were prepared and subjected to crystal structure investigation using X-ray technique. The photoelectrochemical behavior of these TiO2/V2O5 was investigated by photolysis of aqueous suspensions of these oxides containing [Fe(CN)6]4-. X-ray diffraction analysis indicated that the TiO2 crystallites grow in the (1 0 1) direction, while The V2O5 crystallites seem to be growing in the (4 2 0) direction, with increasing concentration of V2O5. Photolysis studies show that photochemical activities that maintained the [Fe(CN)6]4/[Fe(CN)6]3- redox reversibility increased by increasing V2O5 up to 50% and then decreased at greater percentages. Aqueous nano systems used in these studies retained their stability as indicated by the reproducibility of their photo-catalytic activities.

Photoelectrochemical Studies on High Specific Capacitance-Photoactive Interfaces Based on Poly 3,4- Ethylenedioxythiophene/Metal Oxides Assemblies

Inorganic/organic interfaces (IOI) consist of TiO2/PEDOT (poly 3,4-ethylenedioxythiophene) and [PMo12O40]3- or MoO3/PEDOT were subject to photoelectrochemical studies in both aqueous nanosuspensions and in thin solid films. The effects PEDOT modifier caused on the photoelectrochemical behavior of the IOI were investigated using [Fe(CN)6]4- as the photoactive hydrated electron donor agent. Results show that native PEDOT or PEDOT doped with MoO3 thin films increased charge storage capability evident by the high capacitive current. In the case of nano suspensions composed of TiO2/PEDOT the adsorption process of [Fe(CN)6]3- (photolysis product) control of the photoactivity outcome of the IOI assemblies. TiO2/PEDOT shows a lower heterogeneous photochemical response than native TiO2 in short term photolysis times. At longer photolysis times the IOI shows photoactivity greater than that of native TiO2. The interface activities were explained by analyzing the IOI junction characteristics, such as electron affinity, work function and hole/electrons barrier heights. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4-and PEDT contributed to the stability of native TiO2 surfaces.

Photo-Electrochemical Studies on TiO₂-Doped Ce (III/IV) Oxides Nanoparticles in Aqueous Electrolytes

Photoelectrochemical studies on TiO2 doped with Ce2O3 or CeO2 took place in aqueous solutions of [Fe(CN)6]4- as the source of hydrated electrons. Our studies show that doping TiO2 with CeO2 gave better photocatalytic reduction of [Fe(CN)6]3- than TiO2 doped with Ce2O3. However the TiO2 assemblies doped with either Ce(III) or Ce(IV) oxides give less photochemical reduction of [Fe(CN)6]3- that the oxides of pure metals (Ti or Ce). In both cases a lowering of the band gaps of TiO2 was noticed. Immobilized TiO2 doped with Ce oxides on a FTO (Fluorine Ten Oxide) surface gave greater photocurrent with I2/I3– than that recorded for [Fe(CN)6]3-/4- redox systems. Our studies indicate that the TiO2 doped with Ce2O3 or CeO2 maintained photoactivity after being immobilized in thin solid sheets and can be used in all solid state photoelectron-chemical cells.

Photoelectrochemical Production of Hydrogen in Aqueous Suspensions Nanoparticles Composites of CdS/ZnS

Aqueous solutions of mixed CdS/ZnS semiconductor (SC) nanoparticle suspensions in phosphate buffers containing 10 mM [Fe(CN)6]4– were used for photochemical production of hydrogen via hydrated electron intermediates. CdS was doped with varying percentages of ZnS to expand the absorption range of the composite to the UV region. Results show that maximum generation of hydrated electrons by [Fe(CN)6]4– occurs at pH 6. Furthermore, native CdS amorphous nanoparticles give the greatest photocurrent. Studies also show that, in phosphate buffer, the steady state photocurrent was directly proportional to the CdS content in the mixture of CdS/ZnS. The aqueous nano-systems sustained their stability as indicated by the reproducibility of their photocatalytic activities. Solar radiated assemblies of CdS/ZnS/ [Fe(CN)6]4– sustained cyclic systems for continuous hydrogen production.

Photoelectrochemical Studies at CdS/PTTh Nanoparticles Interfaces

Photo-activities at Inorganic/Organic/Interfaces (IOI) consisting of CdS/ Polyterthiophine (PTTh) assemblies were investigated in nanoparticle suspension and in thin solid film forms. The effects PTTh modifier cause on the photoelec-trochemical behavior of the IOI were investigated using [Fe(CN)6]4- as photoactive hydrated electron donor agent. Results show that the adsorption process of [Fe(CN)6]3- (photolysis product) control the photoactivity outcome of IOI assemblies. CdS/PTTh shows lower heterogeneous photochemical response than native CdS. Native CdS amorphous nanoparticles adsorb more [Fe(CN)6]3- with very steady adsorption /desorption process than the modified ones. The interface activities were explained by analyzing the IOI junctions’ characteristics, such as electron affinity, work function and hole/electrons barrier heights. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4- and PTTh contributed to the stability of native CdS surfaces.