Catalytic performance of perovskite-like oxide doped cerium(La_(2-x)Ce_xCoO_(4±y)) as catalysts for dry reforming of methane

A series of oxides(La_(2-x)Ce_xCoO_(4±y)) with perovskite-like structure were prepared by the Pechini sol–gel method for dry reforming of methane reaction(DRM). The prepared catalysts were characterized by BET, XRD,TGA, H_2-TPR and SEM. Experimental results indicate that the addition of Ce can impact both sample morphology and catalytic performance significantly compared with La_2CoO_4 catalyst, and LaCeCoO_4 presented the highest catalytic ability among all the samples. The Ce addition tends to increase the specific surface area of La_(2-x)Ce_xCoO_(4±y)from 0.2 to 8.5 m^2·g^(-1), suggesting that LaCeCoO_4 catalyst contained more well-dispersed active sites and more space to reaction. Moreover, the catalytic performance and anti-coking ability were substantially improved after Ce addition during DRM, which may be attributed to the decrease of LaCoO_3 particle size and growth of oxygen storage capacity, respectively.

An in-situ room temperature route to CuBiI_4 based bulk-heterojunction perovskite-like solar cells

Both bismuth and copper are non-toxic and earth-abundant elements suitable for lead-free halide perovskite-like photovoltaic devices. Here, we report a highly facile route for in-situ producing copper-bismuth-iodide(CuBiI4) thin films directly on ITO substrate at room temperature, by utilizing a Bi-Cu alloy layer as precursor. X-ray diffraction and transmission electron microscopy(TEM) results verified the formation of well crystallized CuBiI4 thin films with [222] orientation. The transient photovoltage(TPV) analysis revealed that the CuBiI4 is an n-type semiconductor with a suitable band gap of ~1.81 eV, preferable to photoelectric conversion compared with CH3NH3PbI3. It is very interesting that the subsequent spin-coating process of the classical Spiro-MeOTAD organic solution with TBP and acetonitrile resulted in a dense and smooth CuBiI4:SpiroMeOTAD bulk-heterojunction film. The preliminarily fabricated simple sandwich structures of ITO/CuBiI4:Spiro-MeOTAD/Au hybrid solar cell devices displayed efficient photovoltaic performance with the PCE up to 1.119% of the best sample. The room temperature direct metal surface elemental reaction(DMSER) method may provide a new insight for all-inorganic lead free perovskite-like AaBbXx compounds and high performance photovoltaic devices.

Surfactant-aided hydrothermal preparation of La(2-x)Sr_xCuO_4 single crystallites and their catalytic performance on methane combustion

Perovskite-like oxide La2-xSrxCuO4 （x = 0, 1） single crystallites with microrod-like morphologies and tetragonal crystal structures were prepared hydrothermally at 240 ℃ with poly（ethylene glycol） （PEG） or hexadecyltrimethyl ammonium bromide （CTAB） as a surfactant and after calcination at 850 ℃. The physicochemical properties of the materials were characterized by means of XRD, BET, SEM, TEM/SAED （selected-area electron diffraction）, XPS and H2-TPR techniques. It is found that doping Sr2＋ to La2CuO4 lattice enhanced the catalytic activity for methane combustion and the LaSrCuO4 catalyst derived from PEG is the best among the tested ones. It is concluded that factors, such as adsorbed oxygen species concentration, reducibility and surface area, determined the catalytic performance of such single-crystalline materials.

A comparative investigation of NdSrCu_(1-x) Co_x O_(4-δ) and Sm_(1.8) Ce_(0.2) Cu_(1-x) Co_x O_(4-δ) (x:0–0.4) for NO decomposition

A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ （x： 0–0.4） with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption （NO-TPD）. The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1？x Co x O 4-δ ones possessed excessive oxygen （i.e., over-stoichiometric oxygen）; with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 〉 NdSrCu 0.8 Co 0.2 O 3.736 〉 NdSrCu 0.6 Co 0.4 O 3.789 〉 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 〉 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 〉 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3＋ /Cu 2＋ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.

Transport and Magnetic Properties of Perovskite-Type Manganite (La_(0.8-x)Ce_x Sr_ (0.2))_ (0.97)MnO_3

Phase structures, the transport ana magnetic properties of the Perovskite-type manganite （La0.8-x CexSr0.2）0.97 MnO3（x = 0 - 0. 26） prepared by La2O3 containing CeO2 with different contents were studied. Experiments show that the compounds consist of a magnetic perovskite phase and non-magnetic CeO2 and Mn3O4. The resistivity and magnetoresistance ratio （MR） of the samples vary with changing x. Their room-temperature MR reaches -3% - - 14% at the magnetic field of 1 T. For x =0; x =0.037 and x = 0.26 samples, the conductance keeps unchanged basically in a relatively wide temperature range above 600 K, and the result shows that it is feasible for producing SOFC cathode materials with these samples.

Catalytic combustion of soot particulates over La_(2-x)K_xNiMnO_6 catalysts

Nanosized La2-xKxNiMnO6 catalysts with ABO3 type perovskite-like structure were prepared by auto-combustion method using citric acid as a ligand to control particle size and morphology.The structures and properties of these perovskite-like oxides were investigated by X-ray powder diffraction（XRD）and temperature-programmed reduction（TPR）.The catalytic activities for soot combustion were evaluated by temperature- programmed oxidation（TPO）with pure O2 and O2/NOx as oxidant,respectively.In the La2-xKxNiMnO6 catalysts,the partial substitution of K at A-site leads to an increase of the concentrations of high valence cation and oxygen vacancy,which enhance the catalytic activity for soot combustion.The optimal substitution amount of K was equal to x=0.4 among these samples.Tp（peak temperature）in O2-TPO profile was 420-C and Tp in O2/NOx-TPO profile was 370-C over La1.6K0.4NiMnO6 catalyst for soot particulates combustion under loose contact conditions between catalyst and soot.

The Potential Game-Changer:A Concept-to-Proof Study on D:A Heterojunction-Free Organic Photovoltaics

Since 1986,the donor-acceptor (D:A) heterojunction has been regarded a necessity for high-efficiency organic photovoltaics (OPVs),due to its unique advantage in compensating the intrinsic limitations of organic semiconductors,such as high exciton binding energy and poor ambipolar charge mobility. While this adversely causes tremendous non-radiative charge recombination and instability issues,which currently become the most critical limits for commercialization of OPVs. Here,we present a concept-to-proof study on the potential of D:A heterojunction free OPV by taking advantage of recent progress of non-fullerene acceptors. First,we demonstrate that the “free carriers” can be spontaneously generated upon illumination in an NFA,i.e.,the 6TIC-4F single layer. Second,the 6TIC-4F layer also exhibits good ambipolar charge transporting property. These exceptional characteristics distinguish it from the traditional organic semiconductors,and relieve it from the reliance of D:A heterojunction to independently work as active layer. As a result,the subsequent OPV by simply sandwiching the 6TIC-4F layer between the cathode and anode yields a considerably high power conversion efficiency ~1%. Moreover,we find the D:A heterojunction free device exhibits two order of magnitude higher electroluminescence quantum efficiency and significantly reduced VOC loss by 0.16 eV compared to those of the D:A BHJ structure,validating its promise for higher efficiency in the future. Therefore,our work demonstrates the possibility of using D:A heterojunction-free device structure for high performance,that can potentially become the next game changer of OPV.

The complex oxides with octahedral structures:Existence areas and phase transitions

The experimental and calculated data on the existence of complex oxides in solid state with the octahedral structures of four families,namely perovskites,Bi-containing layered perovskite-like ones,tetragonal tungsten bronzes and pyrochlores,and about their phase transitions are systematized and summarized on the basis of the quasi-elastic or geometric models of these structures.It has been established that similar existence areas and similar correlations between the interatomic bond strains in their structures,on the one hand,and the temperatures of their ferroelectric or antiferroelectric phase transitions,on the other hand,are observed for all of them,despite the differences in the compositions and structures of these oxides,but taking into account their similar parameters.

Grain landscape and dielectric properties of ceramics based on sodium,calcium,strontium niobates,depending on the synthesis and sintering conditions,and mechanical processing

The properties studying results of ceramics based on strontium,calcium and sodium niobates,which vary from the conditions of synthesis,sintering,and mechanical processing,are presented.The evolution of the grain structure of objects is traced depending on their phase filling during concentration changes in the composition and thermodynamic prehistory(preparation conditions).