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Tuc Altaf, Cigdem/0000-0001-9036-5836, Flexible, self-powered, and fast-responsive photoelectrochemical photodetector (PEC-PD) devices are needed in optoelectronic applications. Although the PD devices constructed from heterojunction of zinc oxide (ZnO) and inorganic halide perovskite (CsPbBr3)-type perovskite displayed astonishing performance in the field, the sensitivity of the perovskite layer to environmental conditions restricts the wide application. Herein, we present a study for the preparation of a wide light spectrum (367-499 nm) sensitive PEC-PD devices built from the heterostructure of Mn-doped ZnO nanorod (ZnONR) and CsPbBr3 on both rigid and flexible substrates using ionic conductive polymer electrolyte. The PEC-PD performance parameters of the self-powered PEC-PD device such as responsivity (R), Detectivity (D*), and sensitivity (S%) have been calculated as 95.12 mAW-1, 2.83x1012 Jones and 8.04x106%, respectively. In addition to these parameters, the fast light response for rise/decay time (tau rise/ tau decay) which is an important parameter for PD applications was (10.62 ms/42.9 ms) observed. The resulting PEC-PD device demonstrated durability over 2500 cycles under simulated sunlight and upon 500 bending cycles at different angles., The authors would like to thank TUBITAK 2218-118C551 for financial support., TUBITAK [2218-118C551]

In this work, we report a self-powered quasi-solid-state photodetector (PD) device prepared from flexible two-dimensional (2D) nanocomposites of a zinc oxide nanowire (ZnO-NW) in various weight percents (5, 10, 30, 50%) and Ti3C2Tx (MXene) paper, constructed with manganese (Mn)-doped zinc oxide nanorods (ZnO NRs) using an ionic gel electrolyte and carbon paper. All PD performance tests revealed that 5% ZnO-MXene-based devices were superior to the other samples. The maximum detectivity of 1.44 x 10(13) Jones at 367 nm (0.1 mW cm(-2)) and zero bias was calculated for the 5% ZnO-MXene-based device. Additionally, a very high on/off ratio of nearly 10(6), which is approximately 35-fold higher than that of the 50% ZnO-MXene-based PDs, was achieved for 5% ZnO-MXene PD at a zero bias under 367 nm (2.52 mW cm(-2)) illumination. The rise time for this device was 9.25 ms. Furthermore, the PD device exhibited excellent stability by enduring 1000 s of light on/off cycles. As a result, a simple, compact, and cost-effective self-powered ZnO-NW:MXene-based PD configuration showed fast photoresponse and excellent detecting performance., Trkiye Bilimsel ve Teknolojik Arastirma Kurumu [122F390]; TUBITAK, N.D.S. and M.S. would like to acknowledge the partial financial support of TUBITAK under research contract number 122F390.

Commercialization of photoelectrochemical (PEC) water-splitting devices requires the development of large-area, low-cost photoanodes with high efficiency and photostability. Herein, we address these challenges by using scalable fabrication techniques and porous transport layer (PTLs) electrode supports. We demonstrate the deposition of W-doped BiVO4 on Ti PTLs using successive-ionic-layer-adsorption-and-reaction methods followed by boron treatment and chemical bath deposition of NiFeOOH co-catalyst. The use of PTLs that facilitate efficient mass and charge transfer allowed the scaling of the photoanodes (100 cm2) while maintaining ~90 % of the performance obtained with 1 cm2 photoanodes for oxygen evolution reaction, that is, 2.10 mA cm−2 at 1.23 V vs. RHE. This is the highest reported performance to date. Integration with a polycrystalline Si PV cell leads to bias-free water splitting with a stable photocurrent of 208 mA for 6 h and 2.2 % solar-to-hydrogen efficiency. Our findings highlight the importance of photoelectrode design towards scalable PEC device development.

In this work, we report a self-powered quasi-solid-state photodetector (PD) device prepared from flexible two-dimensional (2D) nanocomposites of a zinc oxide nanowire (ZnO-NW) in various weight percents (5, 10, 30, 50%) and Ti3C2Tx (MXene) paper, constructed with manganese (Mn)-doped zinc oxide nanorods (ZnO NRs) using an ionic gel electrolyte and carbon paper. All PD performance tests revealed that 5% ZnO-MXene-based devices were superior to the other samples. The maximum detectivity of 1.44 x 10(13) Jones at 367 nm (0.1 mW cm(-2)) and zero bias was calculated for the 5% ZnO-MXene-based device. Additionally, a very high on/off ratio of nearly 10(6), which is approximately 35-fold higher than that of the 50% ZnO-MXene-based PDs, was achieved for 5% ZnO-MXene PD at a zero bias under 367 nm (2.52 mW cm(-2)) illumination. The rise time for this device was 9.25 ms. Furthermore, the PD device exhibited excellent stability by enduring 1000 s of light on/off cycles. As a result, a simple, compact, and cost-effective self-powered ZnO-NW:MXene-based PD configuration showed fast photoresponse and excellent detecting performance., Trkiye Bilimsel ve Teknolojik Arastirma Kurumu [122F390]; TUBITAK, N.D.S. and M.S. would like to acknowledge the partial financial support of TUBITAK under research contract number 122F390.

This study reports the preparation of zinc oxide nanorod arrays (ZnO NRAs) on patterned glass substrates via the photolithography method to be used as photoanode material for photoelectrochemical photodetector (PEC PD) applications. The excellent alignment of ZnO NRAs has been observed on the patterned substrates via photolithography. Therefore, the effects of circular patterns having different circle diameters (D:20 µm, 2D:40 µm, 4D:80 µm in diameter) and the distance between circles have been investigated in the PEC PD application. ZnO thin films have been prepared by physical vapor deposition using RF magnetron sputtering. Subsequently, the photoresist has been spun on the ZnO layer, followed by exposure to laser light with 375 nm of wavelength. Vertically aligned ZnO NRAs have been grown on the patterned surface by the facile chemical bath deposition method. Surface analysis of patterned substrates of ZnO NRAs has been performed via optical profilometry. First, the effects of the diameter changes of the circles and the distance between the circles in the pattern on PEC PD performance have been verified in various electrolytes. PEC PD measurements have been performed under applied potential (-1V to +0.4V voltage (vs. Ag/AgCl)) at UV irradiation and dark condition to obtain responsivity, selectivity, and detectivity parameters. Second, ZnO NRAs have been coated with an indium sulfide (In2 S3 ) thin film layer using the ultrasonic spray pyrolysis method to shift the light absorption through the visible region. It has been determined that In2 S3 -coated ZnO NRAs provided the highest charge transfer at the photoanode/electrolyte interface when the diameter of circles is D in pattern and the distance between the circles is decreased., The authors would like to thank TUBITAK Defense Industries Research and Development Institute for the usage of the cleanroom

The production of photodetectors that can provide their own power needs and can be adapted to different application conditions is very important for next-generation optoelectronic devices. Three-dimensional (3D) ZnO in nanoflower (NF) morphology was synthesized to be sensitized with all-inorganic perovskite for the application of self-powered photodetector (PD) devices. Consequently, we report high-performance and air-/solvent-stable ZnO/CsPbBr3/S-g-C3N4-based PD devices in three different forms: as a solid-state form and photoelectrochemical (PEC)-type PDs in both liquid electrolyte systems and a quasi-solid-state (QSS) form. The solid-state configuration of the PD device generated a photocurrent density of 150 mu A at 367 nm, while the detectivity and responsivity values were calculated as 3.4 x 10(15) Jones and 0.25 AW(-1), respectively. The device was confirmed to be air-stable upon stability tests for 90 days, retaining more than 65% of its initial current density. The self-power ability of ZnO/CsPbBr3/S-g-C3N4 PEC-type PDs was proven for both liquid electrolyte systems and QSS forms. Open cell voltage and sensitivity as high as 250 mV and 3.96 x 10(7)%, respectively, were obtained for QSS ZnO/CsPbBr3/S-g-C3N4 PEC-type PDs. This study proved that the ZnO/CsPbBr3/S-g-C3N4-based PEC PD devices with high performance in the range of 367 to 460 nm can be adapted to meet different application requirements in a wide range from liquid electrolyte systems to solid- and QSS-type electrolyte systems., T?rkiye Bilimsel ve Teknolojik Arastirma Kurumu [118C551]; TUBITAK, C.T.A., N.D.S., and M.S. would like to acknowledge the partial financial support from TUBITAK under research contract number 118C551.

La transcription des symboles et des caractères spéciaux utilisés dans la version originale de ce résumé n’a pas été possible en raison de limitations techniques. La version correcte de ce résumé peut être lue en PDF. La production d'hydrogène solaire photoélectrochimique (PEC) est une voie prometteuse pour convertir l'énergie solaire en énergie chimique en utilisant des semi-conducteurs comme matériaux actifs. Dans le processus de fractionnement de l'eau PEC, l'efficacité de conversion de l'énergie solaire en énergie hydrogène est principalement déterminée par l'absorption de la lumière des photocatalyseurs, la séparation et la migration des porteurs photogénérés et la catalyse de surface. Cependant, les performances sont encore loin d'être satisfaisantes en raison d'une plage d'absorption limitée et d'une recombinaison de charge rapide. Par conséquent, l'élargissement efficace de la plage spectrale d'absorption des photocatalyseurs et la suppression de la recombinaison de charge des paires électron-trou photogénérées sont deux moyens importants d'améliorer l'efficacité de conversion photoélectrique des matériaux semi-conducteurs à base de PEC. Par rapport aux photocatalyseurs à composant unique, les photocatalyseurs à hétérostructure qui combinent au moins deux matériaux fonctionnels dans un système ont reçu plus d'attention au cours de la dernière décennie grâce à l'effet synergique. Cette thèse explore comment les matériaux semi-conducteurs hétérostructurés interagissent les uns avec les autres, et comment des propriétés telles que la gestion de la lumière et l'injection de charge peuvent être contrôlées en modulant de manière appropriée les interfaces des nanomatériaux pour améliorer les performances du dispositif PEC. Les points quantiques à zéro dimension (0D QD) ont été reconnus comme l'un des photosensibilisateurs les plus prometteurs pour la fabrication de photoélectrodes, grâce à leurs propriétés optiques uniques et évolutives où l'absorption

La séparation de l'eau par la technologie photoélectrochimique (PEC) est un moyen écologique et durable de produire de l'hydrogène. Les matériaux semi-conducteurs, en tant que composants centraux des cellules de fractionnement de l'eau PEC, ont une influence décisive sur l'efficacité de la conversion solaire-hydrogène du dispositif. En tant que semi-conducteur le plus courant, l'oxyde métallique (MO) a fait l'objet d'une grande attention en raison de sa remarquable stabilité (photo)-électrochimique, de son faible coût, de la position favorable de ses bords de bande et de la large distribution de ses bandes interdites. Malgré ces caractéristiques attrayantes, son application dans la séparation de l'eau PEC souffre toujours de ses inconvénients intrinsèques, tels que le désordre et la non-uniformité, qui limitent sérieusement l'efficacité et les performances du système PEC. Cependant, les méthodes traditionnelles de synthèse de la MO ne parviennent pas à améliorer ces caractéristiques. Par conséquent, il est vraiment urgent de développer une nouvelle méthode de synthèse de MO, qui fournira facilement des architectures poreuses stables, une phase contrôlée, ainsi qu'un contrôle utile des dimensions (1-D, 2-D et 3-D) de la MO pour améliorer leurs performances et leur efficacité dans les applications de séparation de l'eau. En tant que matériaux hybrides organiques-inorganiques cristallins émergents, les cadres métallo-organiques (MOF) ont été largement utilisés comme précurseurs sacrificiels pour la synthèse de MO en raison de leurs composites aux nanostructures et compositions chimiques accordables et contrôlables. Dans cette thèse, nous avons développé un certain nombre de photoélectrodes à base de MO par la méthode du modèle MOF et évalué leurs performances dans la génération d'hydrogène par séparation d'eau PEC. Le dioxyde de titane (TiO2) est devenu l'un des semi-conducteurs MO les plus étudiés pour la séparation de l'eau PEC depuis 1972. Cependant, le c

The application of halide perovskites in the photoelectrochemical generation of solar fuels and feedstocks is hindered by the instability of perovskites in aqueous electrolytes and the use of expensive electrode and catalyst materials, particularly in photoanodes driving kinetically slow water oxidation. Here, solely earth-abundant materials are incorporated to fabricate a CsPbBr3-based photoanode that reaches a low onset potential of +0.4 VRHE and 8 mA cm−2 photocurrent density at +1.23 VRHE for water oxidation, close to the radiative efficiency limit of CsPbBr3. This photoanode retains 100% of its stabilized photocurrent density for more than 100 h of operation by replacing once the inexpensive graphite sheet upon signs of deterioration. The improved performance is due to an efficiently electrodeposited NiFeOOH catalyst on a protective self-adhesive graphite sheet, and enhanced charge transfer achieved by phase engineering of CsPbBr3. Devices with >1 cm2 area, and low-temperature processing demonstrate the potential for low capital cost, stable, and scalable perovskite photoanodes.

The CQDs + Ni(OH)2/BiVO4 photoanode was fabricated by introducing CQDs with fluorescence and optical properties. The CQDs + Ni(OH)2/BiVO4 photoanode exhibited a low water oxidation onset potential (∼0.2 V vs. RHE) and a photocurrent density of 3.05 mA cm−2 at a voltage of 1.23 V vs. RHE, which is about 2.5 times than that of the unmodified BiVO4 electrode, and the charge injection efficiency is 65%. Surface dynamics test showed that CQDs + Ni(OH)2/BiVO4 photoanode had higher charge transfer rate and lower charge recombination rate than BiVO4 electrode. As a cheap and stable catalyst for water oxidation, Ni(OH)2 combined with CQDs can effectively improve the migration of photogenerated electrons and holes, thereby improving the photoelectrochemical (PEC) water oxidation activity of the photoanode.

Band bending modification of metal/semiconductor hybrid nanostructures requires low-cost and effective designs in photoelectrochemical (PEC) water splitting. To this end, it is evinced that gradient doping of Au nanoparticles (NPs) inwards the ZnO nanorods (NRs) through thermal treatment facilitated faster transport of the photo-induced charge carriers. Systematic PEC measurements show that the resulting gradient Au-doped ZnO NRs yielded a photocurrent density of 0.009 mA/cm(2) at 1.1 V (vs. NHE), which is 2.5-fold and 8-fold improved compared to those of Au-sensitized ZnO and the as-prepared ZnO NRs, respectively. The IPCE and ABPE efficiency tests confirmed the boosted photoresponse of gradient Au-incorporated ZnO NRs, particularly in the visible spectrum due to the synergistic surface plasmonic effect of Au NPs. A gradient Au dopant profile promoted the separation and transfer of the photo-induced charge carriers at the electrolyte interface via more upward band bending according to the elaborated electrochemical impedance spectroscopy and Kelvin probe force microscopy analyses. Therefore, this research presents an economical and facile strategy for preparing gradient plasmonic noble NP-incorporated semiconductor NRs, which have excellent potential in energy conversion and storage technologies.

Photoelectrochemical (PEC) water splitting, one of the most promising technologies for clean hydrogen generation, has drawn considerable attention over the past few decades. Achieving simultaneous highly efficient and stable unassisted PEC water splitting has been the “holy grail” in clean and renewable fuel generation. State-of-the-art photoelectrodes have shown relatively high efficiencies (∼10–20%). Still, their stability is limited due to photoelectrode chemical instability, electrolyte resistance, mass transfer issues, and an often unoptimized experimental setup. In this work, we present a framework and a set of protocols for conducting long-term stability experiments and further provide details on several critical factors such as light source calibration, choosing the right counter electrode, the configuration of the PEC cell, and photoelectrode sample preparation.

Mesoporous TiO2 nanostructures and TiO2−Au nanocomposites with stabilized Au nanoparticles are synthesized by the template sol-gel process. The effects of synthesis conditions on the particle size, electronic structure, morphology, composition, and texture of prepared materials are determined. TiO2- and TiO2−Au-based electrodes are shown to be photoactive in the wavelength range of 250–412 nm and in the methylene blue (MB) photodecomposition and feature high catalytic activity in an oxygen electroreduction reaction. The presence of hydroxyl and carboxylate groups in the amorphous phase is the key factor affecting the photosensitivity of our TiO2 nanostructures and contributing to enhancement of their photoactivity in the MB photodecomposition reaction. Due to their catalytic activity and consistent performance in the oxygen electroreduction reaction, the TiO2 nanostructures and TiO2−Au nanocomposites can be considered as promising materials for use in electrochemical oxygen sensors with application to aqueous solutions.

Robust, cost-effective, and scalable solution based chemical bath deposition and ultrasonic spray pyrolysis methods have been applied to fabricate one dimensional (1D) zinc oxide nanowire (ZnO NW) and zinc stannate (ZTO) heterojunction thin films to be employed in photoelectrochemical (PEC) water splitting and UV photodetector (PD) systems. PEC performance evaluation in a three-electrode cell confirmed the positive effect of ZTO on ZnO NW-based photoanode enhancing incident photon-to-current efficiency (IPCE%) two-folds of the pristine ZnO NW at 367 nm wavelength. Responsivity (Rs) and detectivity (D*) values of the pristine ZnO NW-based PD have been increased from 0.5 A.W?1 and 0.5 × 1012 Jones to 1.7 A.W?1 and 1.0 × 1012 Jones with ZTO layer, respectively. © 2022 Elsevier B.V., This research was supported by TUBITAK-BIDEB-2218 Program No.118C551., 118C551

Robust, cost-effective, and scalable solution based chemical bath deposition and ultrasonic spray pyrolysis methods have been applied to fabricate one dimensional (1D) zinc oxide nanowire (ZnO NW) and zinc stannate (ZTO) heterojunction thin films to be employed in photoelectrochemical (PEC) water splitting and UV photodetector (PD) systems. PEC performance evaluation in a three-electrode cell confirmed the positive effect of ZTO on ZnO NW-based photoanode enhancing incident photon-to-current efficiency (IPCE%) two-folds of the pristine ZnO NW at 367 nm wavelength. Responsivity (Rs) and detectivity (D*) values of the pristine ZnO NW-based PD have been increased from 0.5 A.W?1 and 0.5 × 1012 Jones to 1.7 A.W?1 and 1.0 × 1012 Jones with ZTO layer, respectively. © 2022 Elsevier B.V., This research was supported by TUBITAK-BIDEB-2218 Program No.118C551., 118C551

To achieve a sustainable development especially in energy harvesting, storage and utilization, tremendous efforts have been made toward renewable green energy carriers, such as hydrogen and ammonia, having attracted substantial attentions to the production of H2 and NH3 via a photoelectrochemical (PEC) procedure, which is very promising to convert solar energy into fuel. In this thesis, the foundation of PEC process especially for water splitting and nitrogen reduction are firstly summarized, including basic mechanisms, performance assessment, impacting factors, existing challenges, and corresponding strategies, etc. Besides, the earth-abundant inexpensive cuprous oxide integrated with a highly polymerized red carbon nitride as photocathodes for PEC water splitting is prepared and systematically investigated. A p-n heterojunction is constructed between cuprous oxide and red carbon nitride especially with a distinctive weak electron exchange via the Cu+ in cuprous oxide and C=N-C group in red carbon nitride, leading to lower resistance of charge transfer and faster mass transfer rate and further an improved PEC performance.

Layered film architectures fabricated through liquid phase processing technologies enjoy great interest for the development of optoelectronic and photoelectrochemical devices, whereby aspects of sustainability are becoming of increased importance. In this presentation we show that carbon nanostructures, such as graphene oxide, carbon nanotubes and carbon dots with their unique electrical and optical properties can be sustainably processed from surfactant-free aqueous dispersions into layered photoelectrodes. Effects of nanostructurization for the development of functional hybrids and environmentally friendly water-based dispersions, as well as the relevance of interface interactions for attaining enhanced charge-transfer and photoelectrochemical performance of the photoelectrode with respect to water-splitting activities are discussed.

A new photoelectrochemical (PEC) system by means of adding sodium sulfite (Na2SO3) was developed to treat sewage. The PEC system simultaneously promoted pharmaceuticals and personal care products (PPCPs) degradation, H2 evolution and E. coli disinfection using an optimized, visible–light driven BiVO4 photoanode. The PEC reactions were first carried out in 1.5 mM Na2SO3 electrolyte. 92.3% of 2 ppm benzophenone-3 (BZP) was degraded, and 115.36 μmol of H2 was produced in 90 min at 1.0 V vs. Ag/AgCl, which was a significant improvement over cases where the electrolyte was either Na2SO4 or NaCl. The sulfite ions were first activated by holes and then converted into sulfate radicals, which played a dominant role in the degradation of BZP. As the holes were caught by the sulfite, charge separation was also enhanced, increasing H2 evolution. The PEC reactions were also used to treat real sewage, in which case an 82% improvement in the rate constant of BZP degradation, 60% increase of H2 evolution, and 0.78 log enhancement of E. coli disinfection were achieved by adding 1.5 mM Na2SO3. The system was also feasible to degrade various PPCPs, and showed excellent reusability and stability, proving its great potential in sewage treatment. © 2021 Elsevier B.V.

The massive emission of bisphenol A (BPA) has imposed adverse effects on both ecosystems and human health. Herein, nanoporous MoS2@BiVO4 photoanodes were fabricated on fluorine-doped tin oxide (FTO) substrates for photoelectrocatalytic degradation of BPA. The photocurrent density of the optimized photoanode (MoS2-3@BiVO4) was 5.4 times as that of BiVO4 photoanode at 1.5 V vs. Ag/AgCl under visible light illumination, which was ascribed to the reduced recombination of photogenerated charge carriers of the well-designed hybrid structure. 10 ppm of BPA could be completely degraded in 75 min by MoS2-3@BiVO4 photoanode, with a bias of 1.5 V vs. Ag/AgCl and 100 mM of NaCl as the supporting electrolyte. The electron paramagnetic resonance (EPR) and free radicals scavenging experiments confirmed that chlorine oxide radical (•ClO) played a dominant role in the degradation of BPA. 14 intermediates were detected and identified during photoelectrocatalytic degradation of BPA by MoS2-3@BiVO4 photoanode and 3 pathways were proposed based on the above intermediates. The hybrid film exhibited high stability and reusability, and promising application potential in photoelectrocatalytic degradation of organic pollutants in aqueous solution.

Increasing anthropogenic carbon dioxide emissions have prompted the search for photoelectrochemical (PEC) methods of converting CO2 to useful commodity products, including fuels. Ideally, such PEC approaches will be sustained using only sunlight, water, and CO2 as energetic and reactant inputs. However, low peak conversion efficiencies (<5%) have made commercialization of fully-integrated PEC devices prohibitive. Here, a 4 cm2 monolithic PEC device exceeding 10% solar-to-fuel efficiency with principal fuel products of carbon monoxide and hydrogen is reported. The corresponding solar-to-CO and solar-to-H2 efficiencies are 7% and 3.5%, respectively. Screening of a range of operating conditions reveals a tunable product mixture of H2 and CO using a gold electrocatalyst. Accordingly, it is shown that device optimization yields a H2-to-CO ratio of 1:2 commonly present in synthesis gas (syngas). Notably, the modularity and facile fabrication of this device permit the incorporation of a broad array of materials for various applications. For example, the electrocatalyst may easily be swapped to target a different set of products.

One-dimensional (1D) titanium dioxide (TiO2) is prepared by hydrothermal method and incorporated as nanofiller into a hybrid polymer matrix of polyethylene glycol (PEG) and employed as a solid-electrolyte in dye-sensitized solar cells (DSSCs). Mesoporous carbon electrocatalyst with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The 1D TiO2 nanofiller is found to increase the photoelectrochemical performance. As a result, for the mesoporous carbon-based DSSCs, 1D TiO2 hybrid solid-state electrolyte yielded the highest efficiencies, with 6.1% under 1 sun illumination, in comparison with the efficiencies of 3.9% for quasi solid-state electrolyte and 4.8% for commercial TiO2 hybrid solid-state electrolyte, respectively. The excellent photovoltaic performance is attributed to the improved ion diffusion, scattering effect, effective path for redox couple transfer, and sufficient penetration of 1D TiO2 hybrid solid-state electrolyte into the electrode, which results in improved light-harvesting, enhanced electron transport, decreased charge recombination, and decreased resistance at the electrode/electrolyte interface., Emerging Materials

In the present study, highly efficient and stable photocatalysts have been developed in order to achieve both organic material degradation and sunlight-driven hydrogen generation. More specifically, we investigated the influence of the surface wettability and types of the precursor anionic species on the morphology of the three-dimensional (3D) hierarchical zinc oxide (ZnO) nanostructures. It has been observed that nitrate and acetate based anionic sources resulted with the hand fan like and nanosheet morphologies, respectively. Adhesion of the ZnO nanostructures on the FTO coated glass has been improved via potassium hydroxide treatment, which also affected the morphology of the ZnO films. Well-adhered photoelectrodes for solar water splitting on FTO coated glass substrates with high applied photon-to-current efficiency have been prepared via simple and cost effective chemical bath deposition method. Finally, ZnO nanopowders with two different morphologies have been synthesized via also chemical bath deposition. These nanopowders were used to photocatalytic degradation of methyl orange dye and very high degree of degradation (95%) was achieved using ZnO-Acetate nanopowders, which had morphology of microspheres with nanosheets. © 2017 Elsevier B.V.

The strong but narrow-bandwidth absorption spectra of organic semiconductors make them excellent candidates for semi-transparent solar cell applications in which color specificity is important. In this study, using a hybrid heterojunction combining the transparent inorganic semiconductor copper thiocyanate (CuSCN) with organic semiconductors (C70, PC70BM, C60, ITIC, IT-4F, or Y6), we show that simple color-tunable solar cells can be fabricated in which the transmission spectrum is determined solely by choice of the organic semiconductor. Using a joint electrical-optical model, we show that it is possible to combine the unique attributes of high photovoltage and color tunability to use these heterojunctions as photovoltaic windows in tandem photoelectrochemical (PEC)-photovoltaic (PV) cells. We demonstrate that this configuration can lead to a reduction in the parasitic absorption losses in the PEC-PV cells and, thus, to solar-to-hydrogen efficiencies (>3%) that are higher than that predicted using the traditionally used architecture in which the PV is placed behind the PEC.

Generation of hydrogen using photoelectrochemical (PEC) water splitting has attracted researchers for the last two decades. Several materials have been utilized as a photoanode in a water splitting cell, including ZnO due to its abundance, low production cost and suitable electronic structure. Most research attempts focused on doping ZnO to tailor its properties for a specific application. In this work, atomic layer deposition (ALD) was used to precisely dope ZnO with hafnium (Hf) in order to enhance its PEC performance. The resultant doped materials showed a significant improvement in PEC efficiency compared to pristine ZnO, which is linked directly to Hf introduction revealed by detailed optical, structural and electrical analyses. The photocurrent obtained in the best performing Hf-doped sample (0.75 wt% Hf) was roughly threefold higher compared to the undoped ZnO. Electrochemical impedance spectroscopy (EIS) and open-circuit potential-decay (OCPD) measurements confirmed suppression in photocarriers' surface recombination in the doped films, which led to a more efficient PEC water oxidation. The enhanced PEC performance of Hf-doped ZnO and effectiveness of the used metal dopant are credited to the synergistic optimization of chemical composition, which enhanced the electrical, structural including morphological, and optical properties of the final material, making Hf-doping an attractive candidate for novel PEC electrodes.

The capabilities of soft x-ray absorption (XAS), soft x-ray emission spectroscopy (XES), resonant inelastic soft x-ray scattering (RIXS), and their application to characterization of solar energy materials are presented. We have discussed some recent developments of in-situ soft x-ray spectroscopy cells, which enable the investigation of critical solid/liquid or solid/gas interfaces in chemical and electrochemical processes under real-world practical conditions. In particular, in-situ soft x-ray spectroscopies can be utilized to probe the formation of intermediate species, charge separation upon illumination of sunlight and electron transfer to the interfacial reactions. A number of examples using soft x-ray spectroscopies to study these solar energy and catalytic materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the energy conversion and energy storage systems.

La population humaine mondiale est actuellement de 7,8 milliards. Ces chiffres représentent un nombre record depuis la formation de la Terre et il est prévu d’augmenter de 3 milliards supplémentaires au cours des 30 prochaines années. Avec, la recherche de la prospérité induira une poussée pour une demande énergétique plus élevée dans le monde entier. Cependant, la consommation d’énergie du siècle dernier nous a déjà montré comment elle a provoqué la pollution des écosystèmes terrestres et le changement climatique. En fait, les historiens tiennent cela au fait que nous vivons maintenant l'Anthropocène, l'ère géologique pendant laquelle l'activité humaine a un impact dominant sur le climat et l'environnement. Cette situation remet en cause nos modes de conversion et de consommation d'énergie à base de combustibles fossiles. On s'attend donc à ce qu'un changement structurel significatif du système énergétique soit le moteur de l'avenir des activités industrielles et économiques. Au fur et à mesure que nous nous dirigeons vers des systèmes de conversion d'énergie plus durables, le développement des nouvelles technologies devrait s'envoler dans la communauté scientifique afin d'atténuer les externalités négatives des technologies actuelles. Parmi les énergies renouvelables, les technologies solaires promettent d'exploiter une plus grande part de l'énergie solaire en la convertissant directement en électricité ou en la stockant dans de nouveaux carburants propres tels que les batteries et les piles à hydrogène. Alors que les technologies photovoltaïques sont déjà entrées sur le marché, de nouveaux types de technologies avec une meilleure empreinte environnementale sont en cours de développement et de recherche. La production d'hydrogène renouvelable (H₂) induite par la division de l'eau par photoélectrochimie solaire (PEC) a également un grand potentiel pour les applications de stockage, mais la production de H₂ est confrontée au défi d'atteindre des performances plus él

Developing highly efficient and stable photoelectrochemical (PEC) water-splitting electrodes via inexpensive, liquid phase processing is one of the key challenges for the conversion of solar energy into hydrogen for sustainable energy production. ZnO represents one the most suitable semiconductor metal oxide alternatives because of its high electron mobility, abundance, and low cost, although its performance is limited by its lack of absorption in the visible spectrum and reduced charge separation and charge transfer efficiency. Here, we present a solution-processed water-splitting photoanode based on Co-doped ZnO nanorods (NRs) coated with a transparent functionalizing metal–organic framework (MOF). The light absorption of the ZnO NRs is engineered toward the visible region by Co-doping, while the MOF significantly improves the stability and charge separation and transfer properties of the NRs. This synergetic combination of doping and nanoscale surface functionalization boosts the current density and functional lifetime of the photoanodes while achieving an unprecedented incident photon to current efficiency (IPCE) of 75% at 350 nm, which is over 2 times that of pristine ZnO. A theoretical model and band structure for the core–shell nanostructure is provided, highlighting how this nanomaterial combination provides an attractive pathway for the design of robust and highly efficient semiconductor-based photoanodes that can be translated to other semiconducting oxide systems.

This study reports the decoration of zinc oxide (ZnO) nanosheets with copper indium sulfide (CuInS2) via sequential metal deposition and post sulfurization methods for photoelectrochemical solar cell application. The three dimensional (3D) ZnO nanosheets are hydrothermally grown on conductive glass substrates by chemical bath deposition. Then, copper/indium metallic alloy is deposited via magnetron sputtering and annealed at high temperature in the presence of elemental sulfur to form CuInS2 absorber on the surface of 3D nanosheets. Photoelectrochemical measurements indicate that the decoration of CuInS2 layer over the ZnO nanosheets results in significant increase in the photocurrent density to 28 mA cm?2 (at 0.5 V vs Ag/AgCl) leading a remarkable amount of hydrogen generation during solar water splitting process, 1387 ?mol measured at 0 V vs Ag/AgCl under 1 sun-illumination for 4 h. © 2018 Elsevier B.V.

Colloidal semiconductor nanocrystals (NCs), especially cadmium (Cd)- and lead (Pb)-containing ones, have been proved to be the promising materials for photoelectronic energy conversion applications. However, the high toxicity and cost of these materials restrict their widespread use. Zinc (Zn)-containing colloidal semiconductor NCs are non-/less toxic and environmentally friendly materials, manifesting in stimulating optical and electronic properties with relevance to a broad scope of applications including light-emitting diodes (LEDs), sensors, photocatalysts, and more. In this Review, we elaborate on the shape control of Zn-containing colloidal semiconductor NCs achieved by a variety of wet-chemical synthetic approaches. Moreover, the formation of core-shell, doped, and hybrid structures based on Zn-containing colloidal semiconductor NCs allow for the optimization of their functionalities, which underpin stimulating photoelectronic energy conversion applications in quantum-dot LEDs (QLEDs), photodetectors, and photocatalysis. Zn-containing colloidal semiconductor NCs that combine the green chemistry with sustainable developments possess a bright future.

The water oxidation capability of the promising photoanode bismuth vanadate (BiVO4) is hampered by poor bulk electron transport and by high rates of charge recombination at the semiconductor/electrolyte interface. Here, we demonstrate that a dual modification of BiVO4 by: (i) annealing in a hydrogen-containing environment and (ii) coating with FeOOH overlayer substantially enhances the water oxidation ability of BiVO4 photoanodes. Hydrogen treated, FeOOH coated BiVO4 photoanodes exhibit a water oxidation photocurrent density of 2.16 mA cm−2 at 1.23 VRHE, which is 5 times higher than for untreated BiVO4 films. Moreover, they showed an impressive low photocurrent onset potential of −0.11 VRHE. A stable photocurrent was observed for 1 h of water oxidation measurement at 1.23 VRHE under 1 Sun illumination. The enhanced photocurrent of FeOOH/H:BiVO4 photoanode is ascribed to an improved bulk charge transport, as confirmed by impedance spectroscopy measurements and Mott-Schottky analysis. The cathodic shift of the onset potential originates from a lowering of the flat band potential and from an improvement of the charge transport at the semiconductor/electrolyte interface. The dual modification strategy used here offers a simple but effective approach of improving the water oxidation performance of BiVO4.

Light-driven water-splitting to generate hydrogen and oxygen from water is typically carried out in an electrochemical cell with an external voltage greater than 1.23 V applied between the electrodes. In this work, we examined the use of a concentration/chemical bias as a means of facilitating water-splitting under light illumination without the need for such an externally applied voltage. Such a concentration bias was created by employing a pH differential in the liquid electrolytes within the O2-generating anode half-cell and the H2-generating cathode half-cell. A novel, stretchable, highly ion-conductive polyacrylamide CsCl hydrogel was developed to connect the two half-cells. The key feature of the cell was the half-cell electrodes, which comprised thin-film conducting polymer composites that were previously designed to maximize light-driven catalysis at moderate pH. Upon being connected with the hydrogel in the presence of light irradiation (0.25 sun intensity on each electrode), the half-cells spontaneously produced hydrogen and oxygen from water, without the need for an externally applied voltage bias greater than 1.23 V. The cell operated reliably and efficiently for 14 h of continuous testing. These results demonstrate the fundamental feasibility of light-driven water-splitting in a photoelectrochemical concentration cell when employing electrodes that operate efficiently at moderate pH, even with low levels of light illumination. The designed conducting polymer composites proved ideal in that regard.

The transition metal, nickel is a favourable material to create combination with chalcogenides elements (S, Se and Te) to become either binary or ternary transition metal chalcogenide such NiSe2, NiSe, NiS2 and Ni3Se. Throughout some observation from the previous research regarding the synthesis of ternary transition metal chalcogenide thin film for photoelectrochemical application, the combination of nickel with two chalcogenide elements; S and Se are rarely found due to the nature of selenium and sulphur. In this work, NiSSe thin film is being synthesis onto indium tin oxide (ITO) glass substrates using electrodeposition technique and the structural and optical properties of the films are studied. The resulted thin films are characterized using X-ray diffraction analysis and scanning electron microscope to determine the crystallographic and morphological properties. Optical are also being analysed for their bandgap values in other to determine the suitability of NiSSe thin film for photoelectrochemical properties. Results proved that nickel sulfoselenide thin films are polycrystalline in nature with a good uniformity. The intersection point for the optical analysis gave the direct bandgap. Well-adherent and dark-coloured thin films are derived from the cathodically electrodeposition by using potential in the reduction region. Experimental results proved NiSSe thin films are capable to be used in photoelectrochemical cell application.

The development of efficient and stable photoelectrodes keeps on being critical in the implementation of practical water splitting devices. Sol-gel synthesized tungsten trioxide thin film electrodes modified with ytterbium have been prepared on conducting glass substrates. All the obtained electrodes were found to be composed of monoclinic WO3, which is the photoactive crystal phase of WO3 for water oxidation. The photoelectrochemical behavior of both WO3 and WO3:Yb nanostructured electrodes in 0.1 M HClO4 is apparently characterized by a low degree of recombination. Ytterbium addition to tungsten trioxide improves its photoelectrochemical response as larger photocurrents are obtained without a significant change of the onset potential. This behavior is attributed primarily to a surface effect rather than to bulk doping. The addition of H2O2 to the aqueous electrolyte gives rise to both an increment in photocurrent and a shift of the photocurrent onset potential toward less positive values, which can be linked to the fact that hydrogen peroxide acts as an efficient hole scavenger. The implications of these findings in the mechanism of water photooxidation on WO3 are discussed.

The preparation of molybdenum-modified hematite electrodes by means of chemical bath deposition and their photoelectrochemical behavior toward water oxidation are reported in this work. The addition of a molybdenum precursor to the bath solution for hematite deposition induces a remarkable change of morphology in the resulting film from (110)-oriented nanorods to polyhedral nanoparticles. Despite the resulting loss of order, by controlling the Mo/Fe molar ratio in the bath solution, a significant improvement of the water oxidation photocurrent is achieved compared to nanorod pristine hematite electrodes. Such a (photo)electrochemical enhancement is mainly explained by an effective surface state passivation in Mo-modified hematite films. FE-SEM, TEM, XRD, and XPS were employed for electrode structural and morphological characterization.

Photoelectrolysis of water using solar energy into storable and environment-friendly chemical fuel in the form of hydrogen provides a potential solution to address the environmental concerns and fulfill future energy requirements in a sustainable manner. Achieving efficient and spontaneous hydrogen evolution in water using solar light as the only energy input is a highly desirable but a difficult target. In this work, we report perovskite solar cell integrated CdS-based photoanode for unbiased photoelectrochemical hydrogen evolution. An integrated tandem device consisting of mesoporous CdS/TiO2 photoanode paired with a triple-cation perovskite (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) solar cell is developed via a facile fabrication route. The proposed photovoltaic integrated photoanode presents an efficient tandem configuration with high optical transparency to long-wavelength photons and strong photoelectrochemical conversions from short-wavelength photons. On the basis of this integrated tandem device, an unbiased photocurrent density of 7.8 mA/cm2 is demonstrated under AM1.5G illumination.

[ES] A causa de la problemática energética y la sobreexplotación de los recursos naturales, es interesante encontrar nuevos combustibles cuya generación provenga de fuentes de energía renovables, como es el caso del hidrógeno obtenido por vía fotoelectroquímica empleando la energía solar como fuente de energía. Para la formación de hidrógeno por este método, se está investigando el empleo de nanotubos como fotocatalizadores. Sin embargo, estas nanoestructuras presentan en ocasiones bajas eficiencias y, por tanto, actualmente se debe solventar este problema antes de trasladar esta técnica a grandes niveles de producción. Por este motivo, esta investigación se centrará en mejorar las propiedades fotoelectroquímicas de los nanotubos de TiO2 obtenidos mediante anodizado electroquímico en condiciones hidrodinámicas de flujo, a través de la transformación de su estructura cristalina por calentamiento en distintas atmósferas controladas de: aire, argón y nitrógeno. La carecterización de las nanoestructuras de TiO2 se llevará a cabo mediante Microscopía Electrónica de Barrido de emisión de campo y Microscopía Raman confocal. Posteriormente, se caracterizarán sus propiedades electroquímicas y fotoelectroquímicas mediante la técnica de fotón incidente-electrón generado y a partir de la producción fotoelectroquímica de hidrógeno en base a la rotura de la molécula del agua. Además, se estudiará su estabilidad frente a la fotocorrosión. Los resultados obtenidos han demostrado una mejor respuesta de los fotocatalizadores aplicados a la producción de hidrógeno al ser calentados en atmósfera de argón y de nitrógeno con respecto al uso de la atmósfera de aire. Esto es debido al mayor número de vacantes de oxígeno que aparecen durante el calentamiento en atmósfera de argón y la incorporación del nitrógeno a la matriz de TiO2 durante el tratamiento térmico en atmósfera de nitrógeno., [EN] Because of the energy problems and the overexploitation of natural resources, it is interesting to find new combustible whose generation comes from renewable energy sources, such as hydrogen obtained through photoelectrochemical processes using solar power as the energy source. To from hydrogen from this method we use TiO2 nanotubes as the photocatalysts. Nevertheless, these nanostructures present disadvantages in their efficiency so that it is necessary to improve the efficiency before high levels of production. For this reason, this research will focus on the photoeletrochemical propeties of the TiO2 nanotubes by means of anodization using hydrodynamic conditions. Annealing was carried out using air, argon and nitrogen transforming the amorphous structure to a crystalline structure. Subsequently, the characterization of TiO2 nanostructures have been carried out by Field Emission Scanning Electron Microscope and Raman confocal microscopy technique. While for the study of the process efficiency, incident photon to current efficiency technique was used and the photoelectrochemical production of hydrogen was based on the splitting water. In addition, the photo-corrosion resistant test was also performed. The results obtained have shown a better response of the photocatalysts applied to the production of hydrogen which are heated in argon and nitrogen atmospheres, with respect to the use the air atmosphere in the thermal treatment. This is due to the oxygen vacancies that appear during the heating in argon atmosphere and to the adding of nitrogen to the TiO2 lattice during the thermal treatment in nitrogen atmosphere.

Au nanorods (NRs) modified nanostructured TiO2/ITO electrodes have been fabricated and characterized in order to develop a biosensing platform for the photoelectrochemical determination of microRNAs. The proposed method is based on the use of thiolated DNA capture-probes (CPs) immobilized onto Au NR surface. The Au NRs are chemically bound at the surface of TiO2/ITO electrodes by means of the mercaptosuccinic acid linker. Subsequently, the DNA CPs are bound to the Au NR surface through the thiolate group, and reacted with the target RNA sequence. Finally, the obtained biosensing platform is incubated with alkaline phosphatase and L-ascorbic acid 2-phosphate (AAP) enzymatic substrate, for the in situ generation of ascorbic acid (AA). Such AA molecule, coordinating to surface Ti atoms, generates a charge transfer complex, that results in a shift of the UV absorption threshold toward the visible spectral region of the nanostructured TiO2 forming the electrode and, hence, in the occurrence of an absorption band centered at 450 nm. The photoelectrochemical monitoring of the formation of the AA-TiO2 complex, under the visible light of a commercial LED light source, allows the selective and quantitative detection of the target microRNA strands.

Nanostructured Fe2TiO5 thick films were deposited on fluorine-doped tin oxide glass substrate using screen printing technology. Starting hematite and anatase nanopowders were mixed in molar ratios 1:1 and 1:1.5 and calcined in air at 900A degrees C for 2 h to form pseudobrookite, Fe2TiO5. Functional powders and sintered thick films were analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and transmission electron microscopy. UV-Vis analysis enabled determination of the band gap. Separation and transfer efficiency of photogenerated charge carriers was confirmed by the photoluminescence and electrochemical impedance spectra. Even though a slightly high onset oxygen evolution potential of photoexcited film electrode samples in NaOH was obtained, photocurrent densities were high, especially in the presence of H2O2 (similar to 12 mA cm(-2) at 1.7 V RHE). This work shows promise for practical application due to favorable band positions of pseudobrookite and low-cost screen printing technology.

The mechanism of water oxidation to molecular oxygen at the surface of strontiumtitanate, a representative transition-metal oxide photocatalyst, was investigatedusing ultrafast pump-probe spectroscopy and accompanying characterization methods.The dependence of the rate of initial charge transfer on applied potential was investigatedwith transient absorption spectroscopy, revealing a phenomenological transfer coefficientfor this single step of the multi-step water oxidation reaction. Time resolvedinfrared spectroscopy provided the first direct evidence of the molecular character of thefirst intermediate to be a titanium-bound oxyl radical, and revealed interfacial Fano couplingbetween the electrolyte, surface species, and catalyst electronic continuum. Furtherwork combining both transient absorption and time-resolved mid-infrared spectroscopyexposed a minimum of three distinct surface states at the strontium titanate surface,providing insight into the rich chemistry mediated at the catalyst surface. These resultshighlight the intricacies of charge transfer at the surface of these promising materials,provide insight into an important but difficult reaction necessary for any artificialphotosynthetic system, and offer a generalizable paradigm for considering heterogeneousphotochemistry. Finally, preliminary groundwork was done to uncover the mechanismof the carbon dioxide reduction half reaction in a novel inorganic-biological bacterialsystem with potential to produce green chemicals such as carbon-neutral liquid fuels.

A novel structure composed of TiO2 nanowire arrays (NWAs) was designed and synthesized by decorating with graphene-linked graphitic carbon nitride (GCN) layers. It serves as a robust photoanode for high-performance solar-driven water splitting in an alkaline solution. The GCN layers were deposited on TiO2 NWAs by a facile electrophoretic method, producing an interconnected two-dimensional GCN nanosheets/one-dimensional TiO2 NWAs heterostructure. Under simulated solar light illumination (light intensity 100 mW cm−2), the optimal GCN/TiO2 NWAs photoelectrode produces a photocurrent density of 1.7 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE), which is around 2.6 times enhancement from that of pristine TiO2 (0.7 mA cm−2 at 1.23 V vs. RHE). The photo-conversion efficiency of GCN/TiO2 NWAs is up to 0.92 % at a low bias potential 0.50 V versus RHE, 3.6 times higher than pristine TiO2 (0.27 % at 0.59 V vs. RHE). The improved photoelectrochemical activity is mainly because of the improved charge separation and transport within the heterojunction as well as enhanced light absorption. Graphical Abstract: [Figure not available: see fulltext.] © 2016 Springer Science+Business Media Dordrecht

In this study, we report a unique design of nano-porous bismuth vanadate (BiVO4) photoelectrode decorated with graphene linked carbon nitride (GCN) nanosheets and their potential application in solar driven photoelectrochemical water oxidation. Especially, an integrated sandwich-like heterojunction with highly interconnected porous structure, comprising two dimensional GCN sheets and three dimensional BiVO4 was successfully synthesized with significantly enhanced photoelectrochemical activity. The prepared photoelectrode achieves up to 1.98 mA cm−2 (1.23 V vs RHE) under AM 1.5G solar light irradiation, 2.06 times compared with pristine BiVO4 (0.96 mA cm−2 at 1.23 V vs RHE). After deposition of cobalt phosphate nanoparticles as water-oxidation electrocatalyst, a plateau photocurrent of 3.42 mA cm−2 (1.23 V vs RHE) with a maximum photo-conversion efficiency of 1.28% was achieved on the prepared photoanode. The highly improved photoelectrochemical performance can be attributed to suitable band matching facilitating efficient charge separation between GCN and BiVO4 as well as the desirable incorporation of rational designed dimensionality-dependent heterojunction for promoted solar energy utilization. More importantly, the combined experimental results and computational simulations reveal that the strong donor-acceptor coupling between GCN sheets and porous BiVO4 facilitates the separation and transfer of photoinduced electron-hole pairs, accounting for the highly promoted photoelectrochemical performance.

In this study, an efficient heterojunction was constructed by anchoring graphitic carbon nitride quantum dots onto TiO2 nanotube arrays through hydrothermal reaction strategy. The prepared graphitic carbon nitride quantum dots, which were prepared by solid-thermal reaction and sequential dialysis process, act as a sensitizer to enhance light absorption. Furthermore, it was demonstrated that the charge transfer and separation in the formed heterojunction were significantly improved compared with pristine TiO2. The prepared heterojunction was used as a photoanode, exhibiting much improved photoelectrochemical capability and excellent photo-stability under solar light illumination. The photoelectrocatalytic activities of prepared heterojunction were demonstrated by degradation of RhB and phenol in aqueous solution. The kinetic constants of RhB and phenol degradation using prepared photoelectrode are 2.4 times and 4.9 times higher than those of pristine TiO2, respectively. Moreover, hydroxyl radicals are demonstrated to be dominant active radicals during the pollutants degradation. © 2016 Elsevier B.V.

The scalable synthesis of highly transparent and robust sub-monolayers of Co₃O₄ nano-islands, which efficiently catalyze water oxidation, is reported. Rapid aerosol deposition of Co₃O₄ nanoparticles and thermally induced self-organization lead to an ultra-fine nano-island morphology with more than 94% light transmission at a wavelength of 500 nm. These transparent sub-monolayers demonstrate a remarkable mass-weighted water oxidation activity of 2070–2350 A gCo₃O₄ ⁻¹ and per-metal turnover frequency of 0.38–0.62 s⁻¹ at an overpotential of 400 mV in 1 m NaOH aqueous solution. This mixed valent cobalt oxide structure exhibits excellent long-term electrochemical and mechanical stability preserving the initial catalytic activity over more than 12 h of constant current electrolysis and 1000 consecutive voltammetric cycles. The potential of the Co₃O₄ nano-islands for photoelectrochemical water splitting has been demonstrated by incorporation of co-catalysts in GaN nanowire photoanodes. The Co₃O₄-GaN photoanodes reveal significantly reduced onset overpotentials, improved photoresponse and photostability compared to the bare GaN ones. These findings provide a highly performing catalyst structure and a scalable synthesis method for the engineering of efficient photoanodes for integrated solar water-splitting cells.

Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances.

Here, we report photocatalytic CO2 reduction with water to produce methanol using TiO2-passivated InP nanopillar photocathodes under 532 nm wavelength illumination. In addition to providing a stable photocatalytic surface, the TiO2-passivation layer provides substantial enhancement in the photoconversion efficiency through the introduction of O vacancies associated with the nonstoichiometric growth of TiO2 by atomic layer deposition. Plane wave-density functional theory (PW-DFT) calculations confirm the role of oxygen vacancies in the TiO2 surface, which serve as catalytically active sites in the CO2 reduction process. PW-DFT shows that CO2 binds stably to these oxygen vacancies and CO2 gains an electron (-0.897e) spontaneously from the TiO2 support. This calculation indicates that the O vacancies provide active sites for CO2 absorption, and no overpotential is required to form the CO2(-) intermediate. The TiO2 film increases the Faraday efficiency of methanol production by 5.7× to 4.79% under an applied potential of -0.6 V vs NHE, which is 1.3 V below the E(o)(CO2/CO2(-)) = -1.9 eV standard redox potential. Copper nanoparticles deposited on the TiO2 act as a cocatalyst and further improve the selectivity and yield of methanol production by up to 8-fold with a Faraday efficiency of 8.7%.

Group III-nitride is a remarkable material system to make highly efficient and high-power optoelectronics and electronic devices because of the unique electrical, physical, chemical and structural properties it offers. In particular, InGaN-based blue Laser Diodes (LDs) have been successfully employed in a variety of applications ranging from biomedical and military devices to scientific instrumentation and consumer electronics. Recently their use in highly efficient Solid State Lighting (SSL) has been proposed because of their superior beam quality and higher efficiency at high input power density. Tremendous advances in research of GaN semi-polar and non-polar crystallographic planes have led both LEDs and LDs grown on these non-basal planes to rival with, and with the promise to outperform, their equivalent c-plane counterparts. However, still many issues need to be addressed, both related to material growth and device fabrication, including a lack of conventional wet etching techniques. GaN and its alloys with InN and AlN have proven resistant essentially to all known standard wet etching techniques, and the predominant etching methods rely on chlorine-based dry etching (RIE). These introduce sub-surface damage which can degrade the electrical properties of the epitaxial structure and reduce the reliability and lifetime of the final device. Such reasons and the limited effectiveness of passivation techniques have so far suggested to etch the LD ridges before the active region, although it is well-known that this can badly affect the device performance, especially in narrow stripe width LDs, because the gain guiding obtained in the planar configuration is weak and the low index step and high lateral current leakage result in devices with threshold current density higher than devices whose ridge is etched beyond the active region. Moreover, undercut etching of III-nitride layers has proven even more challenging, with limitations in control of the lateral etch dista