Eurasian-Scale Experimental Satellite-based Quantum Key Distribution with Detector Efficiency Mismatch Analysis

The Micius satellite is the pioneering initiative to demonstrate quantum teleportation, entanglement distribution, quantum key distribution (QKD), and quantum-secured communications experiments at the global scale. In this work, we report on the results of the 600-mm-aperture ground station design which has enabled the establishment of a quantum-secured link between the Zvenigorod and Nanshan ground stations using the Micius satellite. As a result of a quantum communications session, an overall sifted key of 2.5 Mbits and a total final key length of 310 kbits have been obtained. We present an extension of the security analysis of the realization of satellite-based QKD decoy-state protocol by taking into account the effect of the detection-efficiency mismatch for four detectors. We also simulate the QKD protocol for the satellite passage and by that validate our semi-empirical model for a realistic receiver, which is in good agreement with the experimental data. Our results pave the way to the considerations of realistic imperfection of the QKD systems, which are important in the context of their practical security.Comment: 8+2 pages, 5+2 figure

Propane Dehydrogenation on Co-N-C/SiO2 Catalyst: The Role of Single-Atom Active Sites

Recently, significant attention has been drawn to carbon materials containing cobalt coordinated to nitrogen, as the promising inexpensive catalysts of a wide range of applications. Given that non-oxidative propane dehydrogenation to propylene (PDH) is also becoming increasingly important, we present the results on PDH over Co-N-C/SiO2 composites. The latter were prepared by pyrolysis of silicone gel enriched with Co(II) salt and triethanolamine. According to XRD, HRTEM and XPS characterizations, the resulting materials consist of metallic cobalt nanoparticles of about 5 to 10 nm size and subnano-sized cobalt species (cobalt single atom sites coordinated to nitrogen/carbon), which are uniformly distributed in mesoporous silica of high specific surface area (up to 500 m2 g−1). The composites demonstrated significant catalytic activity in PDH, which was examined under typical reaction conditions (600 °C, 1 atm) using a fixed bed flow reactor. The subnano-sized Co centers proved to be the real active catalytic sites responsible for the target reaction, while carbon deposition induced by Co nanoparticles provided the catalyst deactivation. It is shown that the catalyst can be reactivated by the treatment with oxygen, which, in addition, notably increases selectivity to propylene (up to 98%) and enhances the catalyst stability in the next operation cycle. This remarkable change in catalytic behavior is shown to be due to the dramatic structural modification of the catalyst upon high-temperature oxidation

Propane Dehydrogenation on Co-N-C/SiO₂ Catalyst: The Role of Single-Atom Active Sites

Recently, significant attention has been drawn to carbon materials containing cobalt coordinated to nitrogen, as the promising inexpensive catalysts of a wide range of applications. Given that non-oxidative propane dehydrogenation to propylene (PDH) is also becoming increasingly important, we present the results on PDH over Co-N-C/SiO2 composites. The latter were prepared by pyrolysis of silicone gel enriched with Co(II) salt and triethanolamine. According to XRD, HRTEM and XPS characterizations, the resulting materials consist of metallic cobalt nanoparticles of about 5 to 10 nm size and subnano-sized cobalt species (cobalt single atom sites coordinated to nitrogen/carbon), which are uniformly distributed in mesoporous silica of high specific surface area (up to 500 m2 g−1). The composites demonstrated significant catalytic activity in PDH, which was examined under typical reaction conditions (600 °C, 1 atm) using a fixed bed flow reactor. The subnano-sized Co centers proved to be the real active catalytic sites responsible for the target reaction, while carbon deposition induced by Co nanoparticles provided the catalyst deactivation. It is shown that the catalyst can be reactivated by the treatment with oxygen, which, in addition, notably increases selectivity to propylene (up to 98%) and enhances the catalyst stability in the next operation cycle. This remarkable change in catalytic behavior is shown to be due to the dramatic structural modification of the catalyst upon high-temperature oxidation

Propane Dehydrogenation over Cobalt Aluminates: Evaluation of Potential Catalytic Active Sites

Non-oxidative propane dehydrogenation (PDH) is becoming an increasingly important approach to propylene production, while cobalt-containing catalysts have recently demonstrated great potential for use in this reaction, providing efficiencies comparable to those of industrially employed Pt- and Cr-based catalytic systems. It is therefore essential to clarify the nature of their active sites, especially since contradictory opinions on this issue are expressed in the literature. In this study, efforts were made to determine the state of Co in cobalt aluminates (CoAl2O4-Al2O3) responsible for PDH under typical operating conditions (600 °C, 1 atm). It is shown that the catalyst with a low cobalt content (Co/Al = 0.1) ensured the highest selectivity to propylene, ca. 95%, while maintaining significant propylene conversion. The structural motifs such as cobalt oxide and metallic cobalt nanoparticles, in addition to tetrahedral Co2+ species in the CoAl2O4 spinel system, were evaluated as potential active-site ensembles based on the obtained catalytic performance data in combination with the XRD, H2-TPR, TEM and XPS characteristics of as-synthesized, spent and spent–regenerated catalysts. It is revealed that the most likely catalytic sites linked to PDH are the Co-oxide forms tightly covering alumina or embedded in the spinel structure. However, additional in situ tuning is certainly needed, probably through the formation of surface oxygen vacancies rather than through a deeper reduction in Co0 as previously thought