TThe present research work focuses on bismuth vanadate (BiVO4) thin films deposited on FTO-coated glasselectrodes through the spin-coating technique, and discusses the influence of different film morphologies(dense and porous) on the physicochemical properties and photoelectrochemical (PEC) performance ofthe as-prepared photoanodes, for the water splitting reaction. The surface recombination phenomenon,which is one of the main issues of BiVO4, has been quantified by means of two distinct approaches: tran-sient photocurrent measurements and electrochemical impedance spectroscopy (EIS). This phenomenonhas resulted to be higher in the porous material, thus a poorer performance has been observed than inthe dense material. In order to increase the BiVO4efficiency, a cobalt phosphate (CoPi) catalyst has beenphoto-electrodeposited onto the best BiVO4electrode, employing an optimized technique and a pho-tocurrent of up to 3 mA/cm2at 1.23 V vs. RHE under neutral pH and 1 sun irradiation (100 mW/cm2)has been achieved. The charge transfer kinetics of the BiVO4photoanodes, with and without CoPi, hasalso been quantified. The beneficial effect of this water oxidation catalyst, as well as the influence of thepreparation method on the uniformity of the film and on its actual performance, is discussed in view ofits prospective application in a real PEC device

In this paper we present an easy, quick and scalable route, based on anodic oxidation, for the preparation of mesoporous SnO₂ as an efficient electrocatalyst for the CO₂ reduction reaction (CO₂RR). Crystallographically interconnected SnO₂ nanocrystals with abundant grain boundaries, high specific surface area and easily accessible porosity result to be active and selective for the CO₂RR. This electrocatalyst shows faradaic efficiency (FE) of about 95% at -0.97 V and -1.06 V vs. reversible hydrogen electrode (RHE) towards the formation of predominant HCOOH and minor CO. A peak FE value of 82 % for the HCOOH production is obtained at -1.06 V vs. RHE. High HCOOH partial current densities of 10.2 mA cm^-2 and 15.3 mA cm^-2 are observed at -0.97 V and -1.15 V vs. RHE, respectively. Thorough electrochemical characterizations demonstrate that the synthesized SnO₂-based gas diffusion electrode allows efficient diffusion of CO₂ even at high kinetics, due to the highly open porous structure. The good understanding of the catalyst behavior is achieved also after the electrode testing and it shows that the proposed preparation route results in a stable and durable material. The here reported promising results can be exploited for developing high-performance and sustainable electrocatalysts with a high potentiality to be implemented in real CO₂ conversion devices.

The sensing capabilities of zinc oxide nano/micro-structures have been widely investigated and these structures are frequently used in the fabrication of cutting-edge sensors. However, to date, little attention has been paid to the multi-sensing abilities of this material. In this work, we present an efficient multisensor based on a single zinc oxide microwire/gold junction. The device is able to detect in real time three different stimuli, UV-VIS light, temperature and pH variations. This is thanks to three properties of zinc oxide its photoconductive response, pyroelectricity and surface functionalization with amino-propyl groups, respectively. The three stimuli can be detected either simultaneously or in a sequence/random order. A specific mathematical tool was also developed, together with a design of experiments (DoE), to predict the performances of the sensor. Our micro-device allows reliable and versatile real-time measurements of UV-VIS light, temperature and pH variations. Therefore, it shows great potential for use in the field of sensing for living cell cultures.

Polyaniline (PANI) was synthesised by oxidation polymerization starting from aniline dimer, thus avoiding the use of a toxic/mutagenic substance such as aniline. In order to work in an aqueous phase, polystyrene sulphonate (PSS) was used as an emulsioning/doping agent. The fine tuning of oxidant quantity allowed the production of PANI in the mixed leucoemeraldine/emeraldine oxidation states. PANI/PSS was solubilised in dimethylsulphoxide and used as ink for the fabrication of inkjet printed tracks, which showed an interesting negative capacitance effect that can be attributed to the presence of different oxidation states and the partial doping obtained by the use of PSS. Negative capacitance devices are extremely attractive in high frequency applications where positive parasitic capacitances have to be compensated.