Synthesis–structure correlations of manganese–cobalt mixed metal oxide nanoparticles

Mixed metal oxides in the nanoscale are of great interest for many aspects of energy related research topics as water splitting, fuel cells and battery technology. The development of scalable, cost-efficient and robust synthetic routes toward well-defined solid state structures is a major objective in this field.While monometallic oxides have been studied in much detail, reliable synthetic recipes targeting specific crystal structures of mixed metal oxide nanoparticles are largely missing. Yet, in order to meet the requirements for a broad range of technical implementation it is necessary to tailor the properties of mixed metal oxides to the particular purpose. Here, we present a study on the impact of the nature of the gas environment on the resulting crystal structure during a post-synthesis thermal heat treatment of manganese–cobalt oxide nanoparticles. We monitor the evolution of the crystal phase structure as the gas atmosphere is altered from pure nitrogen to synthetic air and pure oxygen. The particle size and homogeneity of the resulting nanoparticles increase with oxygen content, while the crystal structure gradually changes from rocksalt-like to pure spinel. We find the composition of the particles to be independent of the gas atmosphere. The manganese–cobalt oxide nanoparticles exhibited promising electrocatalytic activity regarding oxygen evolution in alkaline electrolyte. These findings offer new synthesis pathways for the direct preparation of versatile utilizable mixed metal oxides.

Advances in selective catalytic oxidation of ammonia (NH_(3)-SCO): A review of catalyst structure-activity relationship and design principles

NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Controlling NH_(3) emissions caused by ammonia escaping from mobile and industrial sources can effectively reduce the NH_(3) content in ambient air. Among the various NH_(3) removal methods, the selective catalytic oxygen method (NH_(3)-SCO) is committed to oxidizing NH_(3) to environmentally harmless H_(2)O and N_(2);therefore, it is the most valuable and ideal ammonia removal method. In this review, the characteristics of loaded and core-shell catalysts in NH_(3)-SCO have been reviewed in the context of catalyst structure-activity relationships, and the H_(2)O resistance and SO2 resistance of the catalysts are discussed in the context of practical application conditions. Then the effects of the valence state of the active center, oxygen species on the catalyst surface, dispersion of the active center and acidic sites on the catalyst performance are discussed comprehensively. Finally, the shortcomings of the existing catalysts are summarized and the catalyst development is discussed based on the existing studies.

Geological controls of shale gas accumulation and enrichment mechanism in Lower Cambrian Niutitang Formation of western Hubei, Middle Yangtze, China

The lower Cambrian Niutitang Formation is of crucial importance for shale gas target reservoirs in western Hubei,China;however,little work has been done in this field,and its shale gas accumulation and enrichment mechanism are still unclear.Based on survey wells,outcrop data,and large numbers of tests,the geological conditions of shale gas accumulation were studied;moreover,the factors that influence the gas content were thoroughly discussed.The results show that the Niutitang Formation(Є1n)can be divided into three sections:the first section(Є_(1)n^(1)),the second section(Є_(1)n^(2)),and the third section(Є1n3).TheЄ_(1)n^(2) is the main shale gas reservoir.The deep shelf facies is the main sedimentary facies and can be divided into three main lithofacies:argillaceous siltstone,carbonaceous shale and carbonaceous siliceous rock.The total organic carbon(TOC)content shows gentle growth trends until bottom of theЄ_(1)n^(2) and then decreases rapidly within theЄ_(1)n^(1),and the TOC content mainly ranges from 2%to 4%horizontally.The calcite and dolomite dissolution pores,clay intergranular pores and organic pores are the main pore types and the micropore types are clearly related to the mineral compositions and the TOC content.Vertically,the gas content is mainly affected by the TOC content.Horizontally,wells with high gas contents are distributed only southeast of the Huangling anticline,and the combination of structural styles,fault and fracture development,and the distribution of the regional unconformity boundary between the upper Sinian Dengying Formation(Z2d)and theЄ_(1)n^(2) are the three most important factors affecting the gas content.The favorable areas must meet the following conditions:a deep shelf environment,the presence of theЄ_(1)n^(1),wide and gentle folds,far from large normal faults that are more than 5 km,moderate thermal evolution,and greater than 500 m burial depth;this includes the block with the YD2–ZD2 wells,and the block with the Y1 and YD4 wells,which are distributed in the southern portion of the Huangling anticline and northern portion of the Xiannvshan fault.

Synthesis,characterization and experimental investigation of Cu-BTC as CO_2 adsorbent from flue gas

Porous Cu-BTC material was synthesized by the solvothermal method. Powder X-ray diffraction （PXRD） was used to test the phase purity of the synthesized material and investigate its structural stability under the influence of flue gas components. The thermal stability of the material was determined through thermal gravimetric （TG） analysis. Scanning electron microscopy （SEM） was employed to study the microstructure of the material. Cu-BTC was demonstrated not only to have high CO2 adsorption capacity but also good selectivity of CO2 over N2 by means of packed bed tests. The adsorption capacity of Cu-BTC for CO2 was about 69 mL/g at 22℃. The influence of the main flue gas components on the CO2 capacity of the material were discussed as well.