Photoelectrochemical (PEC) water splitting has attracted great attention during past decades thanks to the possibility to reduce the production costs of hydrogen or other solar fuels, by doing so in ...a single step and powered by the largest source of renewable energy: the sun. Despite significant efforts to date, the productivities of stable semiconductor materials in contact with the electrolyte are limited, pushing a growing scientific community towards more complex photoelectrode structures. During the last decade, several groups have focused on the strategy of incorporating state of the art photovoltaic absorber materials (such as silicon, III-V compounds and chalcogenide-based thin films). The stability of these devices in harsh acidic or alkaline electrolytes has become a key issue, pushing transparent, conductive and protective layer research. The present review offers a detailed analysis of PEC devices from metal oxide electrodes forming a semiconductor-liquid junction to protected and catalyst-decorated third generation solar cells adapted into photoelectrodes. It consists of a complete overview of PEC systems, from nanoscale design to full device scheme, with a special focus on disruptive advances enhancing efficiency and stability. Fundamental concepts, fabrication techniques and cell schemes are also discussed, and perspectives and challenges for future research are pointed out.
The present review offers a detailed analysis of Photoelectrochemical (PEC) devices from metal oxide electrodes forming a semiconductor-liquid junction to protected and catalyst-decorated third generation solar cells adapted into photoelectrodes.
The nanostructured BiVO4 photoanodes were prepared by electrospinning and were further characterized by XRD, SEM, and XPS, confirming the bulk and surface modification of the electrodes attained by W ...addition. The role of surface states (SS) during water oxidation for the as-prepared photoanodes was investigated by using electrochemical, photoelectrochemical, and impedance spectroscopy measurements. An optimum 2% doping is observed in voltammetric measurements with the highest photocurrent density at 1.23 VRHE under back side illumination. It has been found that a high PEC performance requires an optimum ratio of density of surface states (N SS) with respect to the charge donor density (N d), to give both good conductivity and enough surface reactive sites. The optimum doping (2%) shows the highest N d and SS concentration, which leads to the high film conductivity and reactive sites. The reason for SS acting as reaction sites (i-SS) is suggested to be the reversible redox process of V5+/V4+ in semiconductor bulk to form water oxidation intermediates through the electron trapping process. Otherwise, the irreversible surface reductive reaction of VO2 + to VO2+ though the electron trapping process raises the surface recombination. W doping does have an effect on the surface properties of the BiVO4 electrode. It can tune the electron trapping process to obtain a high concentration of i-SS and less surface recombination. This work gives a further understanding for the enhancement of PEC performance caused by W doping in the field of charge transfer at the semiconductor/electrolyte interface.
The development of more efficient electrode materials is essential to obtain vanadium redox flow batteries (VRFBs) with enhanced energy densities and to make these electrochemical energy storage ...devices more competitive. A graphene-modified graphite felt synthesized from a raw graphite felt and a graphene oxide water suspension by means of electrophoretic deposition (EPD) is investigated as a suitable electrode material in the positive side of a VRFB cell by means of cyclic voltammetry, impedance spectroscopy and charge/discharge experiments. The remarkably enhanced performance of the resultant hybrid material, in terms of electrochemical activity and kinetic reversibility towards the VO2+/VO2+, and mainly the markedly high energy efficiency of the VRFB cell (c.a. 95.8% at 25 mA cm−2) can be ascribed to the exceptional morphological and chemical characteristics of this tailored material. The 3D-architecture consisting of fibers interconnected by graphene-like sheets positively contributes to the proper development of the vanadium redox reactions and so represents a significant advance in the design of effective electrode materials.
•Graphene-modified graphite felt as electrode for vanadium redox flow batteries.•Electrophoretic deposition technology from GO suspensions as synthesis procedure.•3D cross-linked architecture consisting on fibers interconnected by graphene sheets.•Enhanced performance in terms of electrochemical activity and kinetic reversibility.
During the last years, oxide semiconductors have shown that they will have a key role in the future of electronics. In fact, several research groups have already presented working devices with ...remarkable electrical and optical properties based on these materials, mainly thin-film transistors (TFTs). Most of these TFTs use indium-tin oxide (ITO) as the material for source/drain electrodes. This paper focuses on the investigation of different materials to replace ITO in inverted-staggered TFTs based on gallium-indium-zinc oxide (GIZO) semiconductor. The analyzed electrode materials were indium-zinc oxide, Ti, Al, Mo, and Ti/Au, with each of these materials used in two different kinds of devices: one was annealed after GIZO channel deposition but prior to source/drain deposition, and the other was annealed at the end of device production. The results show an improvement on the electrical properties when the annealing is performed at the end (for instance, with Ti/Au electrodes, mobility rises from 19 to 25 cm 2 /V ldr s, and turn-on voltage drops from 4 to 2 V). Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), we could confirm that some diffusion exists in the source/drain electrodes/semiconductor interface, which is in close agreement with the obtained electrical properties. In addition to TOF-SIMS results for relevant elements, electrical characterization is presented for each kind of device, including the extraction of source/drain series resistances and TFT intrinsic parameters, such as (intrinsic mobility) and VT i (intrinsic threshold voltage).
Bismuth-based photocatalysts, Bi2WO6, BiVO4, and coupled Bi2WO6/TiO2–P25, have been synthesized by a facile hydrothermal method, characterized, and evaluated for the first time for the selective ...photooxidation of methane to methanol. Several conditions were used in order to better comprehend the reaction mechanism. The obtained BiVO4 is, among the others, the most promising photocatalyst for this reaction, displaying higher CH3OH selectivity and being more stable than the others. When Bi2WO6 was coupled with TiO2, the methane conversion increased; however, overoxidation of CH4 to CO2 predominates. A similar effect is observed when electron scavengers such as O2 or Fe3+ were introduced in the photoreactor as a result of the formation of highly oxidant radicals.
Nitrite ions are shown to have significant influence on the selectivity of the photocatalytic oxidation of methane to methanol. An almost complete inhibition of undesired CO2 has been achieved with ...BiVO4 in the presence of a low concentration of nitrite, which might act both as a UV filter and as a hydroxyl radical scavenger.
The selective oxidation of methane to methanol is achieved by means of a photocatalytic process. For this purpose, designed Bi- and V-containing beta zeolites prepared by incipient wetness ...impregnation have been used under different test conditions. While the zeolite proves to be photoactive under UVC irradiation toward the total oxidation process, the formation of V2O5 on the surface is an effective alternative for modifying the acid–base surface properties, thus significantly decreasing the undesired CO2 formation. At the same time the zeolite framework serves as a scaffold for increasing the surface area and distribution of the metal oxide. Additionally, the addition of low Bi amount favors the formation of a BiVO4/V2O5 heterojunction, which acts as a visible light photocatalyst while at the same leading to total selectivity to methanol at the expense of ethylene formation.
The persistence of malaria hotspots in Datem del Marañon Province, Peru, prompted vector control units at the Ministry of Health, Loreto Department, to collaborate with the Amazonian International ...Center of Excellence for Malaria Research to identify the main vectors in several riverine villages that had annual parasite indices > 15 in 2018-2019. Anophelinae were collected indoors and outdoors for two 12-hour nights/community during the dry season in 2019 using human landing catch. We identified four species: Nyssorhynchus benarrochi B, Nyssorhynchus darlingi, Nyssorhynchus triannulatus, and Anopheles mattogrossensis. The most abundant, Ny. benarrochi B, accounted for 96.3% of the total (7,550/7,844), of which 61.5% were captured outdoors (4,641/7,550). Six mosquitoes, one Ny. benarrochi B and five Ny. darlingi, were infected by Plasmodium falciparum or Plasmodium vivax. Human biting rates ranged from 0.5 to 592.8 bites per person per hour for Ny. benarrochi B and from 0.5 to 32.0 for Ny. darlingi, with entomological inoculation rates as high as 0.50 infective bites per night for Ny. darlingi and 0.25 for Ny. benarrochi B. These data demonstrate the risk of malaria transmission by both species even during the dry season in villages in multiple watersheds in Datem del Marañon province.
•CuO nanowires were grown by thermal oxidation of Cu foils.•Individual nanowires were contacted by focused ion beam/electron beam deposition of Pt.•Higher responses to NH3 than SnO2 nanowire sensors ...were attained.•Gas response of CuO was found to be fully controlled by the presence of adsorbed oxygen species at its surface.
Copper (II) oxide (CuO) is a metal oxide suitable for developing solid state gas sensors. Nevertheless, a detailed insight into the chemical-to-electrical transduction mechanisms between gas molecules and this metal oxide is still limited. Here, individual CuO nanowires were evaluated as ammonia (NH3) and hydrogen sulphide (H2S) sensors, validating the p-type character of this semiconductor. The working principle behind their performance was qualitatively modeled and it was concluded that adsorbed oxygen at the surface plays a key role necessary to explain the experimental data. Compared to their counterparts of SnO2 nanowires, an appreciable sensitivity enhancement to NH3 for concentrations below 100ppm was demonstrated.
The alpaca fiber diameter (FD) varies from 18 to 36 μm, being the finer fiber categories highly appreciated. However, the alpaca fiber presents some limitations in the textile industry due to the ...high incidence of fiber medullation and diameter variability, both reduces the comfort feeling of the garments. Decreasing or even removing medullation could be a possible selection objective in alpaca breeding programs for increasing economic value of the alpaca fiber. Therefore, the present work aimed to estimate genetic parameters regarding medullation traits, as well as the genetic correlations with other economical important traits, to be able to select the appropriate criteria to reduce or remove medullation on alpaca fiber and help to reduce the prickle factor in the garments. The data was collected from 2000 to 2017 and belonged to the Pacomarca experimental farm. There were 3698 medullation records corresponding to 1869 Huacaya and 414 Suri genetic types. The fiber samples were taken from the mid side, and were analyzed in an OFDA 100® device. The traits analyzed were percentage of medullation (PM), medullated fiber diameter (MFD), FD, standard deviation of FD, greasy fleece weight as fiber traits; density, crimp in Huacaya and lock structure in Suri, head conformation, leg coverage as morphological traits; weaning weight and age at first calving as secondary and functional traits. Genetic parameters were estimated via a multitrait restricted maximum likelihood. The heritabilities for PM and MFD were 0.225 and 0.237 in Huacaya genetic type and 0.664 and 0.237 in Suri genetic type, respectively; heritabilities for other traits were moderate for productive and morphological traits, and low to moderate for secondary and functional traits. The genetic correlations PM–FD and MFD–FD were high and favorable in both genetic types, between 0.531 and 0.975; the genetic correlation PM–MFD was 0.121 in Huacaya and 0.427 in Suri. The rest of genetic correlations with other traits were in general moderate and favorable. The repeatabilities were 0.556 and 0.668 for PM, and 0.322 and 0.293 for MFD in Huacaya and Suri genetic types, respectively. As a conclusion, PM was identified to be a good selection criterion, probably combined in an index with FD to reduce prickling factor.
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