Dimethyl sulfide in the atmospheric surface layer of the Equatorial Pacific Ocean

This paper reports a case study of atmospheric stability effect on dimethyl sulfide(DMS) concentration in the air. Investigation includes model simulation and field measurements over the Pacific Ocean. DMS concentration in surface sea water and in the air were measured during a research cruise from Hawaii to Tahiti. The diurnal variation of air temperature over the sea surface differed from the diurnal cycle of sea surface temperature because of the high heat capacity of sea water. The diurnal cycle of average DMS concentration in the air was studied in relation to the atmospheric stability parameter and surface heat flux. All these parameters had minima at noon and maxima in the early morning. The correlation coefficient of the air DMS concentration with wind speed (at 15 m high) was 0. 64. The observed concentrations of DMS in the equatorial marine surface layer and their diurnal variability agree well with model simulations. The simulated results indicate that the amplitude of the cycle and the mean concentration of DMS are dependent on the atmospheric stratifications and wind speed.

Electron delocalization enhances the thermoelectric performance of misfit layer compound(Sn_(1-x)Bi_(x)S)_(1.2)(TiS_(2))_(2)

The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying.Here,we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons.This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range.It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons,indicating that it independently modulates phonon and charge transport properties.These effects collectively give rise to a maximum ZT of 0.3 at 720 K.In addition,we apply the single Kane band model and the Debye–Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound(SnS)_(1.2)(TiS_(2))_(2).

Thermoelectric performance enhancement of(BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

A misfit layer sulfide(BiS)_(1.2)(TiS_(2))_(2) with a natural superlattice structure has been shown to be a promising thermoelectric material,but its high carrier concentration should be reduced so as to further optimize the thermoelectric performance.However,ordinary acceptor doping has not succeeded because of the non-parabolic band structure.In this paper,we have successfully doped chromium ions into the Ti sites,which can maintain or even enhance the high effective mass of electrons so as to effectively improve ZT value.X-ray diffraction analysis,coupled with X-ray photoelectron spectroscopy,shows that chromium has been substituted into titanium sites in TiS2 layers and confirms its ionic state.The chromium doping has successfully reduced the carrier concentration with the subsequent reduction of electrical conductivity.Unlike other acceptor dopants(alkaline earth metals),chromium also enhances Seebeck coefficient and the effective mass,which can possibly be attributed to the formation of additional resonant states near Fermi level.Though the power factor does not improve,the significant reduction in the electronic part of the thermal conductivity leads to a measurable improvement in ZT.

A Rational Design of Heterojunction Photocatalyst Cd S Interfacing with One Cycle of ALD Oxide

Photo-corrosion is one of the major obstacles for CdS application in wet chemical fields, and atomic layer deposition （ALD） has been proposed as an effective way to suppress the corrosion. Here, prior to ALD coating, CdS, one facilely corrosive photocatalyst, was synthesized via hydrothermal synthesis to access the fundamental corrosion mechanism and the according corrosive sites. X-ray photoelectron spectros- copy （XPS） and X-ray diffraction （XRD） demonstrated that the failure of catalytic decomposition of methylene blue originated from the formation of soluble CdSO4 by oxidizing S2 of as-prepared CdS. High resolu- tion transmission electron microscopy （HRTEM） further identified the active sites in the V-shaped regions ofCdS nanoparticles, confirmed by the simulated electric field distribution. To rationally coat oxides on CdS, the right candidates and their thicknesses have been considered by our tunneling model with trans- fer matrix method based on quantum mechanism, upon which the thickness of protective layer should be less than 0.5 nm to maintain a high tunneling probability, and thus one cycle of ALD TiO2 or AbO3 was proposed to passivate the CdS powder to balance the carrier transportation and corrosion suppres- sion. Based on HRTEM results, we found that the active V-shaped region was covered by ALD oxides （TiO2 or AbO3）. For each case, no soluble CdSO4 has been found before and after photocatalytic reactions based XPS measurements. Importantly, we noticed that with the passivation of one cycle of ALD, the catalyst＇s lifetime was elongated up to 〉14 times higher than that of the as-prepared CdS.