Yuxi Guo

Novel g-C 3 N 4 /BiIO 4 heterojunction photocatalysts: synthesis, characterization and enhanced visible-light-responsive photocatalytic activity

The g-C3N4/BiIO4 composite photocatalysts were successfully synthesized using a simple-mixed-calcinations method, and their photocatalytic activities for degradation of rhodamine B (RhB) under visible-light (λ > 420 nm) were investigated for the first time. The crystal structure and optical property of the as-synthesized samples were characterized by XRD, FTIR, SEM, TEM, HRTEM and DRS spectroscopy. The photodegradation experiments indicated that the g-C3N4/BiIO4 composite photocatalyst displays a higher photocatalytic activity than the two individuals, which was also confirmed by the PL spectra and photoelectrochemical experiments. This remarkably improved photocatalytic performance can be attributed to the heterojunction structure of g-C3N4/BiIO4 composites, which possess stronger oxidation and reduction capability, thus resulting in the efficient separation of photoinduced charge carriers as demonstrated in the active species experiments. The present study will be beneficial for the design of high performance photocatalysts.

Origin of strong white electroluminescence from dense Si nanodots embedded in silicon nitride.

Strong white electroluminescence (EL) from SiN-based devices containing Si nanodots with a density of more than 4.6×10(12)cm(2) was investigated. The white EL illustrates enhanced light emission with increasing applied voltage and can be divided into two components, a dominant peak at ~710 nm and weak one at ~550 nm, which are close to those of the PL spectra optically pumped by the 325 and 488 nm lines, respectively. Based on the PL characteristics, we propose that the dominant EL band arises from the band-to-band recombination in the dense Si nanodots where quantum confinement plays a decisive role in the light emission, whereas the weak EL band originates from the radiative Si dangling bond (K0) centers in the silicon nitride matrix.

Plasmon induced Au particle and surface oxidation co-decorated BiOIO3 heteronanostructures with highly promoted photocatalysis and photoelectrochemical properties

Plasmon induced Au nanoparticle and surface oxidation induced co-decorated BiOIO3 heterostructured nanocomposites have been developed via a facile in situ photosynthesis route. The structural and optical properties of the as-prepared photocatalysts were systematically characterized by XRD, XPS, TEM, SEM, UV-Vis DRS and PL. Fascinatingly, the introduction of Au nanoparticles induced not only an enhanced photoabsorption in the visible region, but also the microstructural variation of BiOIO3. The oxidative effect of HAuCl4 resulted in the formation of Bi4+/Bi5+, which led to the increased specific surface area of the products. The photocatalysis and photoelectrochemical properties of the samples were investigated by monitoring the photodecomposition of Rhodamine B (RhB) and photocurrent generation under UV-visible light illumination. The results revealed that Au@BiOIO3 presents drastically enhanced photoreactivity compared with the pristine BiOIO3. The highly improved photochemical properties are ascribed to the synergic contribution of the highly promoted generation and separation of charge carriers induced by the surface plasmon resonance (SPR) effect of Au particles, surface chemical state change, as well as the significantly high surface area that provides more reactive sites. These results are corroborated by the electrochemical impedance spectra (EIS), bode-phase spectra, PL spectra, active trapping and DMPO-assisted ESR measurements. This study not only provides evidence for the feasibility of metallic Au as a SPR co-catalyst of bismuth-based materials, but also furnishes new insights into the multiple effects for enhancing the photochemical properties.

In-depth insight into facet-dependent charge movement behaviors and photo-redox catalysis: A case of {0 0 1} and {0 1 0} facets BiOCl

A central issue in understanding photo-redox catalysis is the facet-dependent charge movement behaviors that include bulk charge separation, surface charge transfer and interfacial charge migration. To get in-depth insight into these complicated processes steered by different exposing facets, herein BiOCl with exposed (001) and (010) facets engaged as the model are investigated. The BiOCl-(010) and BiOCl-(001) single-crystalline sheets are separately synthesized via hydrothermal and hydrolysis routes. In contrast to BiOCl-(010), BiOCl-(001) demonstrates highly promoted photo-redox performance for H2 generation and degradation of pollutants. The facet-dependent charge movement behaviors were surveyed by surface photovoltage spectroscopy (SPV), transient photocurrent, linear sweep voltammetry, continuous wavelength photocurrent, and electrochemical impedance spectrum (EIS). All the photoelectrochemical and photoelectric measurement results reflect that BiOCl-(001) exhibits superior charge separation and migration efficiencies in the whole charge movement process than the BiOCl-(010). Besides, a higher charge carrier density (3.1-fold enhancement) was also observed for BiOCl-(001) compared to BiOCl-(010). Our current work is expected to further our understanding on facet-dependent charge movement behaviors and offer new insight into design of high-performance photocatalytic/photoelectrochemical materials.

Gypsum blocks produced from TiO2 production by-products

ABSTRACT Calcined titanium gypsum was investigated by the ways of XRD (powder X-ray diffraction), XRF (X-ray fluorescence) and TG-DTA (thermogravimetric–differential thermal analyses). It was employed as raw material for making lightweight materials. The influence of cement, amount of water/solid (W/S) ratio, water-reducing agent, citric acid content and the hydration age on the gypsum blocks was investigated. The results showed that the optimum W/S ratio, cement content and water-reducing agent are 0.9, 10% and 2 wt% for the calcined gypsum from titanium gypsum, respectively. The 5.96 MPa was attained after 7 days of ageing. It was also found that the citric acid is inappropriate to be used in the production of gypsum blocks from TiO2 production by-products.