Composition optimization, structural design, and introduction of external magnetic fields into the catalytic process can remarkably improve the oxygen evolution reaction (OER) performance of a catalyst. NiFe2O4@(Ni, Fe)S/P materials with a heterogeneous core–shell structure were prepared by the sulfide/phosphorus method based on spinel-structured NiFe2O4 nanomicrospheres. After the sulfide/phosphorus treatment, not only the intrinsic activity of the material and the active surface area were increased but also the charge transfer resistance was reduced due to the internal electric field. The overpotential of NiFe2O4@(Ni, Fe)P at 10 mA cm–2 (iR correction), Tafel slope, and charge transfer resistance were 261 mV, 42 mV dec–1, and 3.163 Ω, respectively. With an alternating magnetic field, the overpotential of NiFe2O4@(Ni, Fe)P at 10 mA cm–2 (without iR correction) declined by 45.5% from 323 mV (0 mT) to 176 mV (4.320 mT). Such enhancement of performance is primarily accounted for the enrichment of the reactive ion OH– on the electrode surface induced by the inductive electric potential derived from the Faraday induction effect of the AMF. This condition increased the electrode potential and thus the charge transfer rate on the one hand and weakened the diffusion of the active substance from the electrolyte to the electrode surface on the other hand. The OER process was dominantly controlled by the charge transfer process under low current conditions. A fast charge transfer rate boosted the OER performance of the catalyst. At high currents, diffusion exerted a significant effect on the OER process and low OH– diffusion rates would lead to a decrease in the OER performance of the catalyst.

Recent innovations in ambient ionization technology for the direct analysis of various samples in their native environment facilitate the development and applications of mass spectrometry in natural science. Presented here is a novel, convenient and flame-based ambient ionization method for mass spectrometric analysis of organic compounds, termed as the ambient flame ionization (AFI) ion source. The key features of AFI ion source were no requirement of (high) voltages, laser beams and spray gases, but just using small size of n-butane flame (height approximately 1 cm, about 500 oC) to accomplish the rapid desorption and ionization for direct analysis of gaseous-, liquid- and solid-phase organic compounds, as well as real-world samples. This method has high sensitivity with a limit of detection of 1 picogram for propyphenazone, which allows consuming trace amount of samples. Compared to previous ionization methods, this ion source device is extremely simple, maintain-free, low-cost, user–friendly so that even an ordinary lighter (with n-butane as fuel) can achieve efficient ionization. A new orientation to mass spectrometry ion source exploitation might emerge from such a convenient, easy and inexpensive AFI ion source.

No abstract

In this paper, TiO 2 films were coated on the surface of diamond particles using a sol-gel method. The effects of heat treatment temperature on the morphology, composition, chemical bonds, oxidation resistance and compressive strength of diamond particles coated with TiO 2 films were characterized through scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric-differential scanning calorimetry and compressive strength test. The results showed that when the temperature reached 600°C, the amorphous TiO 2 on the diamond particles surface exhibited as a dense anatase film and the Ti-O-C bond formed between TiO 2 and the diamond substrates. When temperature reached 800°C, TiO 2 films were still in anatase phase and part of the diamond carbon began to graphitize. The graphitizated carbon can also form the Ti-O-C bond with TiO 2 film, although TiO 2 film would tend to crack in this condition. Meanwhile, the temperature had a serious influence on the oxidation resistance of diamond particles coated with TiO 2 films in air. When the heat treatment temperature reached 600°C, the initial oxidation temperature of the coated diamond particles reached the maximum value of 754°C. When the diamond particles were oxidized at 800°C for 0.5 h in air, the weight loss rate reached the minimum value of 6.7 wt% and the compressive strength reached the maximum value of 15.7 N.

No abstract