Hongjian Yan

Synthesis and piezoelectric properties of lead-free piezoelectric [Bi0.5(Na1−x−yKxLiy)0.5]TiO3 ceramics

Abstract A new group of lead-free piezoelectric ceramics, [Bi 0.5 (Na 1− x − y K x Li y ) 0.5 ]TiO 3 , were invented. These ceramics were prepared by conventional ceramic sintering technique. The results of X-ray diffraction (XRD) data show that the ceramics possess almost pure perovskite phase with a little unknown phase when y ≤0.20. The measurements of dielectric and piezoelectric properties reveal that the ceramics with high amount of K + and low amount of Li + provide relatively high piezoelectric charge constant d 33 (up to 180 pC/N) and high planar electromechanical coupling factor k p (up to 35.0%). The fabrication technique for these ceramics is stable. It is obvious that the ceramics can be used in practical applications.

A polymer–metal–polymer–metal heterostructure for enhanced photocatalytic hydrogen production

The tightly coupled heterostructure g-C3N4/Au/poly(3-hexylthiophene) (P3HT)/Pt was successfully prepared by a self-assembling method. The heterojunction photocatalyst displayed high activity for hydrogen production from water which contains triethanolamine as an electron donor under visible light irradiation. The samples were characterized by X-ray diffraction (XRD), UV-visible spectroscopy, photoluminescence (PL) spectra analysis and transmission electron microscopy (TEM). The experimental results demonstrated that the g-C3N4/Au/P3HT/Pt structure was conducive to the efficient separation of photo-generated electron–hole pairs, which can be explained by the strong junction of chemical bond between Au and P3HT. The effect of P3HT content on the activity of the photocatalysts was investigated with a series of g-C3N4/Au/P3HT heterostructure samples loaded with Pt as a cocatalyst in triethanolamine aqueous solutions. The optimal P3HT content was determined to be 0.5 wt%, and the corresponding hydrogen evolution rate was 320 μmol h−1.

Light-induced spatial separation of charges toward different crystal facets of square-like WO3

Light-induced preferential migration of electrons and holes to the minor (200) and (020) facets and the dominant (002) facets of square-like WO3, respectively, resulted in the square-like WO3 nanoplates with Pt loaded mainly on dominant (002) facets shows higher photocatalytic activity than that Pt loaded on the minor facets.

Silicon carbide recovered from photovoltaic industry waste as photocatalysts for hydrogen production

In recent years, the focus on creating a dependable and efficient means to recycle or recover the valuable parts from the waste material has drawn significantly attention as an environmentally friendly way to deal with the industrial wastes. The silicon carbide (SiC) crystalline is one of reusable material in the slurry wastes generated during wafer slicing. Here we report the use of recovered SiC from the slurry wastes as photocatalysts to produce hydrogen in the presence of Na2SO3-Na2S as electron donor. The recovered SiC were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy spectra (XPS), UV-vis (UV-vis) spectroscopy, and photoluminescence (PL) spectroscopy. The morphology of SiC loaded with 1wt% Pt as cocatalyst by thermal-reduction method was observed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM). The experimental results reveal that the recovered SiC is mainly consist of 3C-SiC, 6H-SiC and some silicon oxycarbides on the surface of the SiC. The highest hydrogen production rate is 191.8μmolh-1g-1. This study provides a way to recycle crystalline SiC from the discharged waste in the photovoltaic industry and reuse it as photocatalyst to yield hydrogen with the advantage of low energy consumption, low pollution and easy operation.

Photocatalytic O2 production using WO3 nanoparticles prepared by annealing ethylenediamine tungstate/CxNy gel

WO3 nanoparticles have extraordinary potential applications in water oxidation and degradation of organic pollutes. In this paper, we reported a strategy for the synthesis of nano-sized WO3 particles by annealing ethylenediamine tungstate ((ET)/CxNy) gel, which was prepared by condensing (NH4)10(H2W12O42)·4H2O, (CH2NH2)2 and CCl4. The as-synthesized WO3 nanoparticles were characterized by X-ray diffraction, X-ray photon energy spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence, and transmission electron microscopy. The as-synthesized spherically shaped WO3 nanoparticles with sizes of 50–100 nm have high crystallinity and few defects. The photocatalytic performance of the as-synthesized WO3 nanoparticles was tested as O2 evolution from water in the presence of KIO3 as an electron sacrifice reagent. The rate of O2 evolution from water on the as-synthesized WO3 nanoparticles is more than two times higher than that of WO3 derived from annealing ammonium tungstate and is 3.7 times higher than that of commercial WO3. We believe that the WO3 nanoparticles synthesized by this method are promising candidates for application as photocatalytic O2 production systems.

The synergetic effect of dual co-catalysts on the photocatalytic activity of square-like WO3 with different exposed facets

Here we report the controlled selective deposition of Pt and PbOx dual-cocatalysts on the edged (200) and (020) facets and the main (002) facets of square-like WO3 nanoplates, respectively. The remarkably enhanced photocatalytic activities were observed for such assembled photocatalysts in photocatalytic water oxidation. The superior performance can be attributed to not only the light-induced preferential flow of photogenerated electrons and holes onto different facets of the square-like WO3, thus leading to the reduction and oxidation reactions taking place on the corresponding edged and major top facets, but also the selective deposition of suitable oxidation and reduction cocatalysts onto the needed facets of square-like WO3 to reduce the charge recombination and catalyze the redox reactions. These findings will be promising and intriguing for designing high efficiency WO3 system for visible light water splitting.