Novel MnS/(Inx_{x}Cu1−x_{1-x})2_{2}S3_{3} composite for robust solar hydrogen sulphide splitting via the synergy of solid solution and heterojunction

Large photocatalytic hydrogen (H$_{2}$) production from copious waste hydrogen sulphide (H$_{2}$S) can meet the increasing demand for H$_{2}$ in a sustainable manor which is beneficial from both environmental and energy standpoints. In this work, we reported a robust MnS/(In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ composite photocatalyst. Both experimental results and density functional theory (DFT) calculations proved that Cu does not act as a cocatalyst but forms a solid solution ((In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$) in the composites, which plays dual roles in improving the photocatalytic performance of H2S splitting: (i) enhancing solar light absorption, and (ii) promoting the desorption of sulfur (S) adsorbed on the catalyst surface. Moreover, the formation of a heterojunction between γ-MnS and (In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ can significantly improve charge separation and migration in the composites. As a result, the MnS/(In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ exhibits greatly extended visible light absorption up to 599 nm and extraordinarily high photocatalytic H$_{2}$ production under visible light from H$_{2}$S with a maximum rate of 29,252 μmol h$^{-1}$ g$^{-1}$. The corresponding apparent quantum efficiencies (AQE) at 420 and 450 nm are as high as 65.2% and 62.6%, respectively. They are the highest so far for the visible light photocatalytic splitting of H$_{2}$S in the absence of noble-metal co-catalysts

Lithographically fabricated silicon microreactor for operando QEXAFS studies in exhaust gas catalysis during simulation of a standard driving cycle

Selective catalytic reduction of NOx by ammonia over Cu-ZSM-5 was monitored by operando QEXAFS during simulation of the New European Driving Cycle. The required fast temperature transients were realized using a novel silicon microreactor, enabling simultaneous spectroscopic and kinetic analysis by X-ray absorption spectroscopy (XAS) and mass spectrometry (MS). Periods of high temperature were correlated to an increase in both N2 production and change of coordination of Cu sites. This operando approach using Si microreactors can be applied to other heterogeneous catalytic systems involving fast temperature transients

In situ probing of Pt/TiO2_{2} activity in low-temperature ammonia oxidation

The improvement of the low-temperature activity of the supported platinum catalysts in selective ammonia oxidation to nitrogen is still a challenging task. The recent developments in in situ/operando characterization techniques allows to bring new insight into the properties of the systems in correlation with their catalytic activity. In this work, near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando X-ray absorption spectroscopy (XAS) techniques were applied to study Pt/TiO$_{2}$ catalysts in ammonia oxidation (NH$_{3}$ + O$_{2}$ reaction). Several synthesis methods were used to obtain samples with different size of Pt particles, oxidation state of Pt, and morphology of the support. Metal platinum particles on titania prepared by pulsed laser ablation in liquids exhibited the highest activity at lower temperatures with the temperature of 50% conversion of NH$_{3}$ being 150 °C. The low-temperature activity of the catalysts synthesized by impregnation can be improved by the reductive pretreatment. NAP-XPS and operando XANES data do not show formation of PtO$_{x}$ surface layers or PtO/PtO$_{2}$ oxides during NH$_{3}$ + O$_{2}$ reaction. Despite the differences in the oxidation state of platinum in the as-prepared catalysts, their treatment in the reaction mixture results in the formation of metallic platinum particles, which can serve as centers for stabilization of the adsorbed oxygen species. Stabilization of the bulk platinum oxide structures in the Pt/TiO$_{2}$ catalysts seems to be less favorable due to the metal–support interaction

Rhodium oxide surface-loaded gas sensors

In order to increase their stability and tune-sensing characteristics, metal oxides are often surface-loaded with noble metals. Although a great deal of empirical work shows that surface-loading with noble metals drastically changes sensing characteristics, little information exists on the mechanism. Here, a systematic study of sensors based on rhodium-loaded WO₃, SnO₂, and In₂O₃—examined using X-ray diffraction, high-resolution scanning transmission electron microscopy, direct current (DC) resistance measurements, operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and operando X-ray absorption spectroscopy—is presented. Under normal sensing conditions, the rhodium clusters were oxidized. Significant evidence is provided that, in this case, the sensing is dominated by a Fermi-level pinning mechanism, i.e., the reaction with the target gas takes place on the noble-metal cluster, changing its oxidation state. As a result, the heterojunction between the oxidized rhodium clusters and the base metal oxide was altered and a change in the resistance was detected. Through measurements done in low-oxygen background, it was possible to induce a mechanism switch by reducing the clusters to their metallic state. At this point, there was a significant drop in the overall resistance, and the reaction between the target gas and the base material was again visible. For decades, noble metal loading was used to change the characteristics of metal-oxide-based sensors. The study presented here is an attempt to clarify the mechanism responsible for the change. Generalities are shown between the sensing mechanisms of different supporting materials loaded with rhodium, and sample-specific aspects that must be considered are identified

Society, State, Nation and the People in the Democratic South Africa: Two Decades of Illusions in The Practice of Public Administration, Development Planning and Management

The purpose of this article is to provide a conceptual argument in that as South Africa transcended beyond its democratic dispensation, an opportunity was missed in the process leading to transition to define a society, state, nation and the people for sustaining the democratic founding for purposes of public administration practice, development planning and management. That is done by critically portraying South Africa as a society, state, nation and locating the people for governance purposes within a democratic founding. It is argued that attempts are made to rewrite the history of the country with a view of bolstering its societal status, nation, state and the people without a profound context. South Africa has become what it is today due to its history that remains its defining factor if it has to locate its society, state, nation and the people. Having lost that opportunity during transition, governance has become so unwieldy in that those assigned with authority in the governance landscape, tend to confuse the roles of society, nation, state and the people and that eventually strain the fragile democracy by distorting the facts and the role of constitutional apparatus that are instrumental to the country’s democratic founding. The conclusion is rather pessimistic in that as long as these issues are not properly located within the governance landscape; the democratic dispensation remains vulnerable for demise just like other democracies within the African continent with the potential of the middle class hijacking it from the vulnerable poor majority being the people that public administration practice has to serve. DOI: 10.5901/mjss.2015.v6n2s1p61

Lack of Cul4b, an E3 Ubiquitin Ligase Component, Leads to Embryonic Lethality and Abnormal Placental Development

Cullin-RING ligases (CRLs) complexes participate in the regulation of diverse cellular processes, including cell cycle progression, transcription, signal transduction and development. Serving as the scaffold protein, cullins are crucial for the assembly of ligase complexes, which recognize and target various substrates for proteosomal degradation. Mutations in human CUL4B, one of the eight members in cullin family, are one of the major causes of X-linked mental retardation. We here report the generation and characterization of Cul4b knockout mice, in which exons 3 to 5 were deleted. In contrast to the survival to adulthood of human hemizygous males with CUL4B null mutation, Cul4b null mouse embryos show severe developmental arrest and usually die before embryonic day 9.5 (E9.5). Accumulation of cyclin E, a CRL (CUL4B) substrate, was observed in Cul4b null embryos. Cul4b heterozygotes were recovered at a reduced ratio and exhibited a severe developmental delay. The placentas in Cul4b heterozygotes were disorganized and were impaired in vascularization, which may contribute to the developmental delay. As in human CUL4B heterozygotes, Cul4b null cells were selected against in Cul4b heterozygotes, leading to various degrees of skewed X-inactivation in different tissues. Together, our results showed that CUL4B is indispensable for embryonic development in the mouse