Using non-combustion explosion in H2O/DMF to synthesize 3D Structure of ultrathin Bi nanofilm with high catalytic activity for p-nitrophenol reduction.

The synthesis of inorganic micro-/nano-materials by dry combustion is somewhat dangerous since it is performed under high temperature. The ultrathin Bi nanofilms with 3D structures were synthesized using a safe approach of non-combustion explosion in H2O/DMF solution at room temperature and atmospheric pressure. The violent reaction between H2O2 and NH3 · H2O resulted in a non-combustion explosion due to the fast evolution of gases. Then under high temperature and high pressure during solvothermal process, the further slight explosion occurred where the oxygen-containing molecules of H2O2 and NO3 - acted as oxidants, while the hydrogen-containing molecules of NaBH4, NH3 · H2O and DMF acted as reductants. The release of gases was accompanied with BiIII reduction by NaBH4. The 3D structure of ultrathin Bi nanofilms with many void spaces formed due to the explosive force and foams from the sharp liberation of gases. Such ultrathin Bi nanofilms with 3D structure exhibited outstanding catalytic activity for p-nitrophenol hydrogenation which is important to treat the environmental pollution from p-nitrophenol discharge. Within only several seconds p-nitrophenol hydrogenation was completed without delay. The non-combustion explosion exhibits potential applications for the synthesis of 3D ultrathin film materials as high efficient catalysts.

WO3@Bi2WO6/NiWO4 Nanocomposites with Outstanding Visible-Light-Driven Photocatalysis for the Degradation of Organic Dyes.

By hydrothermal reaction, the WO3@Bi2WO6/NiWO4 nanocomposite was prepared by the coprecipitation reaction between Bi3+/Ni2+ and WO2-4 in the presence of urea and PVP. It resulted in the formation of uniform and well-dispersed nanocomposite structures with ultrathin Bi2WO6/NiWO4 nanosheets attached with ultrafine WO3 nanoparticles. The nanocomposites exhibited a wide light absorbance up to 680 nm with low indirect band gaps of 2.54 eV, leading to outstanding photocatalytic efficiency for the degradation of both Rhodamine B (Rh B) and Xylenol Orange (XO) under visible light. With irradiation for only 15 minutes, Rh B was nearly completely degraded. XO, which is difficult to degrade usually, and the strong absorption peak nearly vanishes in about 60 min. The ultrathin Bi2WO6/NiWO4 nanosheets and ultrafine WO3 nanoparticles mean high specific areas and high active sites. A lot of hydroxy groups in WO3@Bi2WO6/NiWO4-III due to the presence of Ni and Bi helps for the formation of ˙OH. According to the ladder theory, the photogenerated e- and h+ by the irradiation light of high wavelength according with band gap can be activated again by that of lower wavelength step by step. The lower wavelength means the higher energy. The broader adsorption means the higher efficiency for energy adsorption and more e- and h+ with higher energy were activated to photocatalytically degrade dyes. This provides new potential to explore nanocomposites for efficient photo-driven degradation of organic dyes under visible light irradiation.

Onsite Substitution Synthesis of Ultrathin Ni Nanofilms Loading Ultrafine Pt Nanoparticles for Hydrogen Evolution.

Here, the ultrathin Ni nanofilms loading ultrafine Pt nanoparticles (Ni/Pt nanocomposites) were synthesized by a simple substitution method for the electrocatalysis of hydrogen evolution reaction (HER). First, the ultrathin Ni nanofilms were prepared by using NaBH4 to reduce Ni salt. Then the ultrafine Pt nanoparticles attached on the surface of the ultrathin Ni nanofilms through the onsite substitution reaction between PtCl6(2-) and Ni element. X-ray photoelectron spectroscopy (XPS) experiment confirmed that Ni in Ni/Pt nanocomposites exists in the form of Ni(OH)2. Transmission electro microscope (TEM) study showed that the ultrafine Pt nanoparticles were sufficiently dispersed and loaded at Ni ultrathin nanofilms. The obtained Ni/Pt nanocomposites exhibited superior activity of HER and good stability in acidic media. It obtained 10 and 100 mA/cm(2) with overpotential of only 36 and 115 mV, respectively. The stability experiment of 20,000 s gave nearly negligible current decrease. On the one hand, the ultrathin Ni nanofilms help to disperse and form the ultrafine Pt nanoparticles. On the other hand, the ultrathin Ni nanofilms help to load the ultrafine Pt nanoparticles as catalyst support and immobilize both of them onto the electrode surface because of the high surface free energy of ultrathin nanofilm and the leading high adsorption ability. In addition, Ni itself exhibited somewhat electrocatalytic activity of HER, which contributed to the whole HER electrocatalysis of Ni/Pt nanocomposites. The excellent electrocatalysis may lead to the decreased consumption of expensive Pt and open up new opportunities for applications in hydrogen energy.