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For a hematite (α-Fe2O3) photoanode, multiple electron/hole recombination pathways occurring in the bulk, interfaces, and surfaces largely limit its low-bias performance (low photocurrent density at low-bias potential) for photoelectrochemical water splitting. Here, a facile and rapid three-step approach is reported to simultaneously reduce these recombinations for hematite nanorods (NRs) array photoanode, leading to a greatly improved photocurrent density at low bias potential. First, flame-doping enables high concentration of Ti doping without hampering the morphology and surface properties of the hematite NRs, which reduces both the bulk and surface recombinations effectively. Second, the addition of a dense-layer between the hematite NRs and fluorine-doped SnO2 substrate effectively reduces the interfacial recombination by suppressing the electron back-injection into electrolyte. Finally, the sequential oxalic acid etching and FeOOH deposition improves both the interface quality between FeOOH electrocatalyst and hematite NRs and the surface catalytic activity. Significantly, the combination of flame-doping, dense-layer deposition, surface etching, and electrocatalyst deposition effectively reduces the multiple electron/hole recombination pathways in a hematite NRs photoanode, which decreases the photocurrent onset potential from 1.02 VRHE to 0.64 VRHE, a reduction of 380 mV. [ABSTRACT FROM AUTHOR]

Doping nanowires (NWs) is of crucial importance for a range of applications due to the unique properties arising from both impurities' incorporation and nanoscale dimensions. However, existing doping methods face the challenge of simultaneous control over the morphology, crystallinity, dopant distribution and concentration at the nanometer scale. Here, we present a controllable and reliable method, which combines versatile solution phase chemistry and rapid flame annealing process (sol-flame), to dope TiO2 NWs with cobalt (Co). The sol-flame doping method not only preserves the morphology and crystallinity of the TiO2 NWs, but also allows fine control over the Co dopant profile by varying the concentration of Co precursor solution. Characterizations of the TiO2:Co NWs show that Co dopants exhibit 2+ oxidation state and substitutionally occupy Ti sites in the TiO2 lattice. The Co dopant concentration significantly affects the oxygen evolution reaction (OER) activity of TiO2:Co NWs, and the TiO2:Co NWs with 12 at% of Co on the surface show the highest OER activity with a 0.76 V reduction of the overpotential with respect to undoped TiO2 NWs. This enhancement of OER activity for TiO2:Co NWs is attributed to both improved surface charge transfer kinetics and increased bulk conductivity. [ABSTRACT FROM AUTHOR]

3D network configurations of copper(II)oxide/titanate nanobelt(CuO/TiNBs) and copper/titanate nanobelt (Cu/TiNBs) were formed usinga two-step polyelectrolyte-assisted synthesis and assembly approach.The photoactivity of the TiNB/CuO and Cu/TiNB composite networks issignificantly enhanced as compared to the activity of 3D structuresformed of pristine TiNB. An efficient, UV–vis-light-inducedelectron transfer at the two-component interface achieved by the intimatecoupling of TiNB with p-type semiconducting CuO and plasmonic Cu nanoparticlesin composite heterostructures facilitates control over the system’sexciton dynamics, which results in highly efficient UV–visphotocatalytic performance of heterostructures. The superior photocatalyticactivity of the metal and semiconductor/semiconductor nanocompositestructures in the visible region is discussed, highlighting the roleof interfacial electron-charge transfer (IFCT) in semiconductor–semiconductor(CuO/TiNB) and surface plasmon resonance (SPR) of Cu nanoparticlesin metal–semiconductor heterostructures. [ABSTRACT FROM AUTHOR]

We report a new flame reduction methodto generate controllableamount of oxygen vacancies in TiO2nanowires that leadsto nearly three times improvement in the photoelectrochemical (PEC)water-splitting performance. The flame reduction method has uniqueadvantages of a high temperature (>1000 °C), ultrafast heatingrate, tunable reduction environment, and open-atmosphere operation,so it enables rapid formation of oxygen vacancies (less than one minute)without damaging the nanowire morphology and crystallinity and iseven applicable to various metal oxides. Significantly, we show thatflame reduction greatly improves the saturation photocurrent densitiesof TiO2nanowires (2.7 times higher), α-Fe2O3nanowires (9.4 times higher), ZnO nanowires (2.0 timeshigher), and BiVO4thin film (4.3 times higher) in comparisonto untreated control samples for PEC water-splitting applications. [ABSTRACT FROM AUTHOR]

The synthesis of sodium bismuth titanate Na0.5Bi0.5TiO3 ( NBT) was studied using the hydrothermal treatment of TiO2 (anatase) and Bi(NO3)3·5H2O in a highly concentrated NaOH solution. The process parameters such as the alkaline conditions, the temperature, the reaction time, and the concentration, as well as the influence of the Bi/Ti ratio and microwave heating were investigated in detail. The as-prepared NBT powders were characterized by X-ray powder diffraction, transmission electron microscopy, energy-dispersive spectrometry, and inductively coupled plasma atomic emission spectrometry. The results show that secondary sodium titanate phases formed along with the NBT phase in the initial stage of the reaction. Their stability was susceptible to the treatment conditions and the Bi/Ti ratio. Pure and well crystallized NBT nanoparticles were obtained after 48 h of reaction time at 200°C, 12 M NaOH, 0.1 M Bi(NO3)3·5H2O and a stoichiometric amount of TiO2 relative to the Bi precursor. A chemical analysis of the powders showed a slight sodium deficiency and bismuth surplus with respect to their nominal composition, i.e., Na: Bi: Ti = 0.47 ± 0.02:0.53 ± 0.02:1.00 ± 0.04. The obtained NBT particles were 50-100 nm in size and exhibited great potential for further integration in composite thin films. [ABSTRACT FROM AUTHOR]

MWO4 (M=Ca, Sr and Ba) scheelite ceramics were studied in terms of their syntheses, sintering, solubility in water, and dielectric response after storing them in dry and moist atmospheres. Of the studied scheelites, the CaWO4 possessed the most promising dielectric properties (ɛ=10.9, Q × f=105 600 GHz), which were stable under the influence of humidity. BaWO4 and SrWO4 exhibited ɛ=9.0 and Q × f values of 32 200 and 62 600 GHz, respectively. The most detrimental effect of the moisture was observed for SrWO4. A sodium impurity present in the SrCO3 reagent (0.35 wt%), which was used for the synthesis of the SrWO4, was found to lower the sintering temperature, enhance the grain growth, and change the other properties of the ceramics, such as humidity susceptibility and solubility in water. The evident tendency of the ceramics to attract water and the increased dissolution of tungstate were observed for all MWO4 scheelite ceramics, which were sintered with the help of Na2CO3 or Li2CO3 (0.5 wt%) sintering aids. The results of the present study suggest that the physical and chemical properties of the ceramics should be carefully considered in the case of using of alkaline-containing sintering aids. [ABSTRACT FROM AUTHOR]

Abstract: This study explores the ultimate limit in dielectric breakdown of SiO2 thin films deposited by gas-phase, plasma-enhanced atomic layer deposition. Thickness-dependent breakdown behaviors similar to conventional, thermally grown SiO2 thin films were observed for the first time on ALD films, where the dominant breakdown mechanisms were impact ionization, trap creation and anode hole injection, respectively. By suppressing these mechanisms, we show a reversible degradation in SiO2 after the onset of Fowler–Nordheim tunneling before permanent dielectric damage occurs. The reversible window was only observable in films thinner than 10nm. The SiO2 thin films ultimately reached irreversible breakdown at a field strength of 2.7Vnm−1, where Si–O bonds were destroyed due to impact ionization and accelerated electrons. [Copyright &y& Elsevier]

The synthesis of sodium bismuth titanate Na0.5Bi0.5TiO3 ( NBT) was studied using the hydrothermal treatment of TiO2 (anatase) and Bi(NO3)3·5H2O in a highly concentrated NaOH solution. The process parameters such as the alkaline conditions, the temperature, the reaction time, and the concentration, as well as the influence of the Bi/Ti ratio and microwave heating were investigated in detail. The as-prepared NBT powders were characterized by X-ray powder diffraction, transmission electron microscopy, energy-dispersive spectrometry, and inductively coupled plasma atomic emission spectrometry. The results show that secondary sodium titanate phases formed along with the NBT phase in the initial stage of the reaction. Their stability was susceptible to the treatment conditions and the Bi/Ti ratio. Pure and well crystallized NBT nanoparticles were obtained after 48 h of reaction time at 200°C, 12 M NaOH, 0.1 M Bi(NO3)3·5H2O and a stoichiometric amount of TiO2 relative to the Bi precursor. A chemical analysis of the powders showed a slight sodium deficiency and bismuth surplus with respect to their nominal composition, i.e., Na: Bi: Ti = 0.47 ± 0.02:0.53 ± 0.02:1.00 ± 0.04. The obtained NBT particles were 50-100 nm in size and exhibited great potential for further integration in composite thin films. [ABSTRACT FROM AUTHOR]