Harvesting the lost photon by plasmonic enhanced hematite-upconversion nanocomposite for water splitting

Converting solar energy to chemical energy in the form of hydrogen via water splitting is one of the promising strategies to solve the global energy crisis. Hematite, a traditional semiconducting oxide photoelectrode, can only absorb UV and visible parts of the solar spectrum, losing 40% infrared energy. In this paper, we report a novel plasmonic enhanced water splitting photoanode based on hematite-lanthanide upconversion nanocomposites to harvest lost photons below the bandgap of hematite. NaYF4:Er, Yb upconversion nanoparticles can upconvert photons from 980 nm to 510 nm–570 nm within the bandgap of hematite. More importantly, a gold nanodisk array with a plasmonic peak centered ∼1000 nm can further boost the photocurrent by 93-fold. It is demonstrated that the excitation process of lanthanide upconversion nanoparticles can be significantly enhanced by plasmonic nanostructures and can thus improve the water oxidation activity via plasmonic enhanced upconversion and hot electron injection, respectively. This new promising strategy will pave the way for plasmonic enhanced lost photon harvesting for applications in solar energy conversion

Fabrication and properties of metalo-dielectric photonic crystal structures for infrared spectral region

We report structural and optical properties of three-dimensional periodic metallic woodpile structures obtained by direct laser writing in dielectric photoresist SU-8 and subsequent electroless coating by a thin Ni film. Signatures of photonic stop gaps were observed in optical reflection spectra of the structures at infrared wavelengths. This study demonstrates that the combination of DLW and chemical infiltration of metals is attractive as a simple and cost-efficient method for the fabrication of metalo-dielectric photonic crystals. © 2007 Optical Society of Americ

Investigation of WO₃ and BiVO₄ Photoanodes for Photoelectrochemical Sensing of Xylene, Toluene and Methanol

Volatile organic compounds (VOCs) are a notable group of indoor air pollutants released by household products. These substances are commonly employed as solvents in industrial operations, and some of them are recognized or suspected to be cancer-causing or mutagenic agents. Due to their high volatility, VOCs are typically present in surface waters at concentrations below a few micrograms per liter. However, in groundwater, their concentrations can reach levels up to thousands of times higher. This study analyses the applicability of the photoelectrochemical (PEC) sensing of VOCs in aqueous medium. Tungsten oxide and bismuth vanadate photoanodes were tested for PEC sensing of xylene, toluene, and methanol in sodium chloride and sodium sulfate electrolytes. The crystalline structure and morphology of coatings were analyzed using XRD and SEM analyses. Photoelectrochemical properties were evaluated using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The results of the study show that aromatic compounds tend to block the surface of the photoelectrode and interfere with the PEC sensing of other substances. WO3 photoanode is found to be suitable for the PEC sensing of methanol under the mild conditions in aqueous electrolytes; however, electrode engineering and assay optimization are required to achieve better detection limits

Reversible hydrogen evolution and oxidation mediated by molecular ion

The paper revisits the mechanism of reversible hydrogen evolution and oxidation reactions (HER and HOR) based on detailed thermodynamic analysis and survey of recent literature data. An assumption about the participation of adsorbed hydrogen atoms as intermediates in these processes, which was made about half a century ago and cannot account for a number of recent experimental observations, is critically analyzed. We propose that adsorbed molecular ion (H+2 )ad acts as intermediate in HER and HOR reactions described by the overall reversible process as follows: 2H3O+ + 2e (H+2)ad H2'' + 2H2O. New insights into the surface electrochemical processes taking place on Pt electrode at E ERHE (RHE { reference hydrogen electrode) as well as electrocatalysis of HER at E < ERHE, i.e. under overvoltage conditions, are obtained. The presented concept explains quantitatively the HER and HOR phenomena observed experimentally

Reversible hydrogen evolution and oxidation on Pt electrode mediated by molecular ion

The mechanism of reversible hydrogen evolution and oxidation reactions (HER and HOR) on Pt electrode is explained and a thermodynamic contradiction related to participation of an adsorbed hydrogen atom as intermediate in these processes is resolved. Modeling invoking a newly proposed intermediate - the molecular hydrogen ion - describes experimental HER and HOR results quantitatively. The findings based on thermodynamic balance and experimental data provide further insights into understanding and interpretation of hydrogen-related surface processes relevant to water splitting, hydrogen generation, and storage

Research on Hydrothermal Decoration of TiO2 Nanotube Films with Nanoplatelet MoS2 Species

In this study, novel electrodes were prepared via decoration of nanotubed TiO2 (TiNT) films with crystalline two- dimensional (2D) MoS2 species by a one-step hydrothermal synthesis approach. Obtained products were characterized in detail by scanning electron microscopy, Raman spectro‐ scopy, U-I measurements and X-ray diffraction techniques. The influence of hydrothermal synthesis conditions on the composition and morphology of the products formed in the solution and within the TiNT film are also discussed. For the first time, acceptable decoration of TiNT films, by tethering 2D layered MoS2 leaflets onto the TiO2 nanotubes, and on the film surface was obtained in the low concentra‐ tion solutions, while the performance of these heterostruc‐ tures in relation to electrochemical hydrogen evolution reaction (HER) was tested. Stable catalytic activity of the obtained 2D MoS2-in-TiNT films was demonstrated under intense HER conditions within the potential window [-0.2 to - 0.4 V] vs. RHE with a notably low Tafel slope of 33 mV/ decade

Interdisciplinaria : revista de psicología y ciencias afines

We report structural and optical properties of three-dimensional periodic metallic woodpile structures obtained by direct laser writing in dielectric photoresist SU-8 and subsequent electroless coating by a thin Ni film. Signatures of photonic stop gaps were observed in optical reflection spectra of the structures at infrared wavelengths. This study demonstrates that the combination of DLW and chemical infiltration of metals is attractive as a simple and cost-efficient method for the fabrication of metalo-dielectric photonic crystals