Some recent studies mainly addressing the preparation and the modification of nanostructured thin films based on WO(3) and their application to photoelectrolysis of aqueous electrolytes are reviewed with the aim of rationalizing the main factors at the basis of an efficient photoanodic response. WO(3) represents one of the few materials which can achieve efficient water photo-oxidation under visible illumination, stably operating under strongly oxidizing conditions; thus the discussion of the structure-related photoelectrochemical properties of WO(3) thin films and their optimization for achieving almost quantitative photon to electron conversion constitutes the core of this contribution.

Anodically grown WO3 photoelectrodes prepared in an N-methylformamide (NMF) electrolyte have been investigated with the aim of exploring the effects induced by anodization time and water concentration in the electrochemical bath on the properties of the resulting photoanodes. An n-type WO3 semiconductor is one of the most promising photoanodes for hydrogen production from water splitting and the electrochemical anodization of tungsten allows very good photoelectrodes, which are characterized by a low charge-transfer resistance and an increased spectral response in the visible region, to be obtained. These photoanodes were investigated by a combination of steady state and transient photoelectrochemical techniques and a correlation between photocurrent produced, morphology, and charge transport has been evaluated

The sintering of nanosize powders of fully stabilized zirconia was investigated using the spark plasma sintering (SPS) method. The influence of sintering temperature, heating rate, direct current pulse pattern, sintering time, and sintering pressure on the final density and grain size of the product was investigated. The dependence of densification on temperature showed a maximum at 1200 °C, resulting with nearly fully dense zirconia with a crystallite size of about 100 nm. Heating rate (50∼300 °C min−1) and sintering time (5–16 min) had no significant influence on the final density and the crystallite size. Pulsing patterns ranging from 2:2 to 48:2 (on:off) had no influence on the density or the crystallite size. However, the applied pressure had a significant influence on the final density but no apparent effect on crystallite size for a sintering temperature of 1200 °C and a hold time of 5 min.

Dense fully stabilized cubic zirconia, sintered by the spark plasma sintering (SPS) method, was characterized through hardness, fracture toughness, and electrical impedance measurements. The effect of sintering temperature on hardness and fracture toughness was evaluated. Samples sintered at 1200°C for 5 min, which had crystallite size of <100 nm, exhibited the highest hardness. Impedance measurements showed an increase in bulk contribution relative to grain boundaries as sintering temperature is increased. Calculation of the activation energy for conduction gave a value, 1.13 eV, in agreement with previously published results.

Nanometric ceria powders doped with 30 mol % samaria are consolidated by a high‐pressure spark plasma sintering (HP‐SPS) method to form > 99 % dense samples with a crystallite size as small as 16.5 nm. A conductivity dependence on grain size was noted: when the grain size was less than 20 nm, only one semicircle in the AC impedance spectra was observed and was attributed to bulk conductivity. In contrast to previous observations on pure ceria, the disappearance of the grain‐boundary blocking effect is not associated with mixed conductivity. With annealing and concomitant grain growth, the samples show the presence of a grain‐boundary effect.

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Precise, reliable, and remote measurement of dissolved oxygen in aqueous media is of great importance for many industrial, environmental, and biological applications. In particular, photoelectrochemical sensors working in differential mode have recently demonstrated promising properties, in terms of stability, sensitivity, and application potential. Here, a new approach is presented, combining visible light sensitivity, effi cient photocurrent generation, and solution-processed fabrication methods of conjugated polymers, with charge carriers selectivity, energetic alignment favorable to effi cient interfacial charge transfer and high surface area achievable by using metal oxide nanostructures. Extensive characterization and optimization of the hybrid organic/inorganic system are carried out, leading to the realization of an oxygen sensor device, based on nanostructured palladium oxide/poly[(9,9-dioctylfl uorenyl-2,7-diyl)-alt -5,5-(4′,7′-di-2thienyl-2′,1′,3′-benzothiadiazole]/[6,6]phenyl-C61-butyric acid methyl ester (PdO/APFO-3:PCBM) as materials of choice. State-of-the-art sensitivity, amounting at −5.87 µA cm −2 ppm −1 , low background signal, in the order of −4.85 µA cm −2 , good electrochemical stability for more than 2 h of continuous functioning and high reproducibility of the signal over the pH 1 to 10 range, are reported, making the hybrid device suitable for several practical uses. The results fully validate the mixed organic/inorganic approach for photoelectrochemical applications, and pave the way for its further exploitation in fi elds like waste water treatment, environmental monitoring, and water splitting.

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