Gas-sensing Properties of Bismuth Iron Molybdate Thin Films

The thin film gas sensors of bismuth iron molybdate were prepared by ion beam sputtering technique. The prototype gas sensors studied have high sensitivity and selectivity to reducing gases, such as ethanol vapor, show a long term stability of response under most operating conditions and insensitivity to atmospheric humidity, and respond quickly comparing to traditional sintered gas sensors. The crystallographic structure and phase composition of these thin films were investigated with XRD, XPS and SEM techniques.

Preparation of Y^(3+)-doped Bi-_(2)MoO_(6) nanosheets for improved visible-light photocatalytic activity: Increased specific surface area, oxygen vacancy formation and efficient carrier separation

Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work, a series of visible-light-driven Y^(3+)-doped BMO(Y-BMO) photocatalysts were synthesized via a hydrothermal method. Degradation experiments on Rhodamine B and Congo red organic pollutants revealed that the optimal degradation rates of Y-BMO were 4.3 and 5.3 times those of pure BMO, respectively. The degradation efficiency of Y-BMO did not significantly decrease after four cycle experiments. As a result of Y^(3+)doping, the crystal structure of BMO changed from a thick layer structure to a thin flower-like structure with an increased specific surface area. X-ray photoelectron spectroscopy showed the presence of highintensity peaks for the O 1s orbital at 531.01 and 530.06 eV, confirming the formation of oxygen vacancies in Y-BMO. Photoluminescence(PL) and electrochemical impedance spectroscopy measurements revealed that the PL intensity and interface resistances of composites decreased significantly, indicating reduced electron–hole pair recombination. This work provides an effective way to prepare high-efficiency Bibased photocatalysts by doping rare earth metal ions for improved photocatalytic performance.

Monte Carlo Simulation of Propylene Selective Oxidation and Ammoxidation overβ-Bi2Mo2O9 Catalyst under Anaerobic Condition

A random walk Monte Carlo （RWMC） simulation model of catalytic particle was established on the basis of the structures of bismuth molybdate catalysts and mechanisms of catalytic reactions with propylene selective oxidation and ammoxidation. The simulation results show that rationality of the RWMC model is proved on the basis of pulse experimental data. One of the most remarkable factors affecting catalytic behavior is the transfer of bulk lattice oxygen, which decides the rate of ammonia-consuming and propylene-consuming. The selectivity of main products reaches the maximum after the reduction of catalysts to a certain degree. It is inferred that catalytic performance improves greatly if the ratio of capacity for dehydrogenation from adsorbed propylene molecule on catalytically active site of molybdenum metal-imido group （Mo=NH） to that on catalytically active site of molybdenum metal-oxo group （Mo=O） becomes much higher.

Boosted photocatalytic removal of NO using direct Z-scheme UiO-66-NH_(2)/Bi_(2)MoO_(6) nanoflowers heterojunction:mechanism insight and humidity effect

In practical applications,relative humidity in the air is a key factor affecting the photocatalytic removal of NO,which is often overlooked in previous studies.Here,we developed a direct Z-scheme UiO-66-NH_(2)/Bi_(2)MoO_(6)heterojunction with a nanoflower-like structure to systematically investigate the effect of relative humidity on photocatalytic removal of NO.The optimized heterojunction for the removal efficiency of NO was 71.6%at1.07 mg·m^(-3)NO concentration(relative humidity=10%),and the generation of NO_(2) was only 1.1%.Interestingly,with the increase in relative humidity,it showed a higher inhibition effect on NO_(2),while the removal of NO decreased slightly(8%),which might be attributed to the affinity effect of NO_(2) with water molecules and the competitive adsorption of H_(2)O and NO on the surface of the heterojunction photocatalysts.Furthermore,the reaction pathways of NO removal at the developed heterojunctions were revealed by in situ DRIFTS analysis.This work provides a novel vision for the development of direct Z-scheme heterojunction photocatalysts to effectively remove NO and inhibit the formation of toxic intermediate NO_(2) under different humidities.

Polar solvent induced in-situ self-assembly and oxygen vacancies on Bi_(2)MoO_(6)for enhanced photocatalytic degradation of tetracycline

It has been proved to be an effective route to efficiently ameliorate photocatalytic performance of catalysts via designing three-dimensional(3D)hierarchical nanostructures and constructing oxygen vacancies(VOs).However,controlling the self-assembly of organization into 3D hierarchical nanostructures while introducing VOs in photocatalysts remains a challenge.Herein,we reported an ethylene glycol(EG)mediated approach to craft 3D hydrangea-structure Bi_(2)MoO_(6)with VOs for efficient photocatalytic degradation of tetracycline.Through manipulating the EG concentration during the fabrication process,the influence of EG concentration on the Bi_(2)MoO_(6)structure was systematically investigated.EG could promote the self-assembly of Bi_(2)MoO_(6)nanosheets to form a 3D hierarchical structure.Compared with 2D nanoplates,3D hierarchical architecture enhanced the surface area and the amount of active sites of Bi_(2)MoO_(6).In addition,the reduction effect of EG on metallic oxide enabled the generation of VOs in Bi_(2)MoO_(6).The VOs adjusted the electronic structure of Bi_(2)MoO_(6),which not only enhanced the light harvesting,but also facilitated the simultaneous utilization of photo-induced electrons and holes to form reactive oxygen species(·O2−and·OH)for the efficient tetracycline decomposition.3D Bi_(2)MoO_(6)hydrangea with VOs achieved a 79.4%removal efficiency of tetracycline after 75 min.This work provides a simple yet robust EG-mediated strategy,which not only promotes the self-assembly of nano-catalysts into 3D hierarchical architectures,but also crafts tunable VOs for highly efficient photocatalysis.

Ni(NH_(3))_(6)^(2+) more efficient than Ni(H_(2)O)_(6)^(2+) and Ni(OH)_(2) for catalyzing water and phenol oxidation on illuminated Bi_(2)MoO_(6) with visible light

Nickel (hydr)oxide (NiOH) is known to be good co-catalyst for the photoelectrochemical oxidation of water,and for the photocatalytic oxidation of organics on different semiconductors.Herein we report a greatly improved activity of Bi_(2)MoO_(6)(BMO) by nickel hexammine perchlorate (NiNH).Under visible light,phenol oxidation on BMO was slow.After NiNH,NiOH,and Ni^(2+)loading,a maximum rate of phenol oxidation increased by factors of approximately 16,8.8,and 4.7,respectively.With a BMO electrode,all catalysts inhibited O_(2)reduction,enhanced water (photo-)oxidation,and facilitated the charge transfer at solidliquid interface,respectively,the degree of which was always NiNH>NiOH>Ni^(2+).Solid emission spectra indicated that all catalysts improved the charge separation of BMO,the degree of which also varied as NiNH>NiOH>Ni^(2+).Furthermore,after a phenol-free aqueous suspension of NiNH/BMO was irradiated,there was a considerable Ni(Ⅲ) species,but a negligible NH_(2)radical.Accordingly,a plausible mechanism is proposed,involving the hole oxidation of Ni(Ⅱ) into Ni(Ⅳ),which is reactive to phenol oxidation,and hence promotes O_(2)reduction.Because NH_(3)is a stronger ligand than H_(2)O,the Ni(Ⅱ) oxidation is easier for Ni(NH_(3))6+than for Ni(H_(2)O)6+.This work shows a simple route how to improve BMO photocatalysis through a co-catalyst.

SINTERING BEHAVIOR AND MICROWAVE DIELECTRIC PROPERTIES OF NOVEL LOW TEMPERATURE FIRING Bi_(3)FeMo_(2)O_(12)CERAMIC

In the present work,a novel low temperature-ring Bi_(3)FeMo_(2)O_(12) ceramic was synthesized via the solid-state reaction method.The monoclinic Bi_(3)FeMo_(2)O_(12) phase can be formed at a low temperature 670℃.A relative density above 96%can be obtained when sintering temperature is above 800℃.The Bi_(3)FeMo_(2)O_(12) ceramic sintered at 845℃ for 2 h shows high microwave dielectric performance with a permittivity-27.2,a Qf value of 14,500GHz and a temperature coefficient of-80 ppm/℃.It might be a candidate for low temperature co-fired ceramics technology.