A Wireless Sensor Network Based Personnel Positioning Scheme in Coal Mines with Blind Areas

This paper proposes a novel personnel positioning scheme for a tunnel network with blind areas, which compared with most existing schemes offers both low-cost and high-precision. Based on the data models of tunnel networks, measurement networks and mobile miners, the global positioning method is divided into four steps: (1) calculate the real time personnel location in local areas using a location engine, and send it to the upper computer through the gateway; (2) correct any localization errors resulting from the underground tunnel environmental interference; (3) determine the global three-dimensional position by coordinate transformation; (4) estimate the personnel locations in the blind areas. A prototype system constructed to verify the positioning performance shows that the proposed positioning system has good reliability, scalability, and positioning performance. In particular, the static localization error of the positioning system is less than 2.4 m in the underground tunnel environment and the moving estimation error is below 4.5 m in the corridor environment. The system was operated continuously over three months without any failures

Elucidating the diffusion pathway of protons in ammonium polyphosphate: a potential electrolyte for intermediate temperature fuel cells

Ammonium polyphosphate (NHPO) is a potential electrolyte material for intermediate temperature fuel cells (150-250 °C). The crystal structure of NHPO, including the H positions, is unravelled by neutron powder diffraction (NPD) data by successive Fourier synthesis from the polyphosphate backbone. The structure consists of zig-zag chains aligned along the [001] directions of tetrahedral phosphate PO units that are connected through O3 atoms with a P-O3-P angle of 126.3(5)°. The proton conductivity mechanism of NHPO is clarified from the thermal evolution of the structure. It shows that some H atoms subtly shift at high temperatures, resulting in a weakening of certain H-bonds, thus increasing the lability of those H atoms involved in the proton conduction mechanism. Conductivity measurements in humid air and H of NHPO show high proton conductivities of 1.2 × 10 to 2.61 × 10 S cm and 2.2 × 10 to 2.69 × 10 S cm, respectively, in the temperature range of 50 °C to 275 °C.C. S. acknowledges the financial support of the National Natural Science Foundation of China (No. 51372271 and 51672029). This work was also supported by the National Key R & D Project from the Ministry of Science and Technology, China (2016YFA0202702) and the Thousand Talents Program for the pioneer researcher and his innovation team in China. J. A. A. acknowledges the Spanish Ministry of Economy and Competitiveness for granting the project MAT2013-41099-R. C. A. L. acknowledges ANPCyT for financial support (project PICT2014-3576)

Recent Advances in Single-Atom Electrocatalysts for Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) plays significant roles in electrochemical energy storage and conversion systems as well as clean synthesis of fine chemicals. However, the ORR process shows sluggish kinetics and requires platinum-group noble metal catalysts to accelerate the reaction. The high cost, rare reservation, and unsatisfied durability significantly impede large-scale commercialization of platinum-based catalysts. Single-atom electrocatalysts (SAECs) featuring with well-defined structure, high intrinsic activity, and maximum atom efficiency have emerged as a novel field in electrocatalytic science since it is promising to substitute expensive platinum-group noble metal catalysts. However, finely fabricating SAECs with uniform and highly dense active sites, fully maximizing the utilization efficiency of active sites, and maintaining the atomically isolated sites as single-atom centers under harsh electrocatalytic conditions remain urgent challenges. In this review, we summarized recent advances of SAECs in synthesis, characterization, oxygen reduction reaction (ORR) performance, and applications in ORR-related H2O2 production, metal-air batteries, and low-temperature fuel cells. Relevant progress on tailoring the coordination structure of isolated metal centers by doping other metals or ligands, enriching the concentration of single-atom sites by increasing metal loadings, and engineering the porosity and electronic structure of the support by optimizing the mass and electron transport are also reviewed. Moreover, general strategies to synthesize SAECs with high metal loadings on practical scale are highlighted, the deep learning algorithm for rational design of SAECs is introduced, and theoretical understanding of active-site structures of SAECs is discussed as well. Perspectives on future directions and remaining challenges of SAECs are presented

Cathode materials for solid oxide fuel cells: a review

The composition and microstructure of cathode materials has a large impact on the performance of solid oxide fuel cells (SOFCs). Rational design of materials composition through controlled oxygen nonstoichiometry and defect aspects can enhance the ionic and electronic conductivities as well as the catalytic properties for oxygen reduction in the cathode. Cell performance can be further improved through microstructure optimization to extend the triple-phase boundaries. A major degradation mechanism in SOFCs is poisoning of the cathode by chromium species when chromium-containing alloys are used as the interconnect material. This article reviews recent developments in SOFC cathodes with a principal emphasis on the choice of materials. In addition, the reaction mechanism of oxygen reduction is also addressed. The development of Cr-tolerant cathodes for intermediate temperature solid oxide fuel cells, and a possible mechanism of Cr deposition at cathodes are briefly reviewed as well. Finally, this review will be concluded with some perspectives on the future of research directions in this area.Peer reviewed: YesNRC publication: Ye

Elucidating the diffusion pathway of protons in ammonium polyphosphate: A potential electrolyte for intermediate temperature fuel cells

Ammonium polyphosphate (NH4PO3) is a potential electrolyte material for intermediate temperature fuel cells (150-250 °C). The crystal structure of NH4PO3, including the H positions, is unravelled by neutron powder diffraction (NPD) data by successive Fourier synthesis from the polyphosphate backbone. The structure consists of zig-zag chains aligned along the [001] directions of tetrahedral phosphate PO4 units that are connected through O3 atoms with a P-O3-P angle of 126.3(5)°. The proton conductivity mechanism of NH4PO3 is clarified from the thermal evolution of the structure. It shows that some H atoms subtly shift at high temperatures, resulting in a weakening of certain H-bonds, thus increasing the lability of those H atoms involved in the proton conduction mechanism. Conductivity measurements in humid air and H2 of NH4PO3 show high proton conductivities of 1.2 × 10-5 to 2.61 × 10-3 S cm-1 and 2.2 × 10-5 to 2.69 × 10-3 S cm-1, respectively, in the temperature range of 50 °C to 275 °C.Fil: Sun, Chunwen. Chinese Academy of Sciences; República de ChinaFil: Lopez, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Alonso, José Antonio. Instituto de Ciencia de Materiales de Madrid; Españ

Recent Progress and Perspectives of Solid State Na-CO₂ Batteries

Solid state Na-CO2 batteries are a kind of promising energy storage system, which can use excess CO2 for electrochemical energy storage. They not only have high theoretical energy densities, but also feature a high safety level of solid-state batteries and low cost owing to abundant sodium metal resources. Although many efforts have been made, the practical application of Na-CO2 battery technology is still hampered by some crucial challenges, including short cycle life, high charging potential, poor rate performance and lower specific full discharge capacity. This paper systematically reviews the recent research advances in Na-CO2 batteries in terms of understanding the mechanism of CO2 reduction, carbonate formation and decomposition reaction, design strategies of cathode electrocatalysts, solid electrolytes and their interface design. In addition, the application of advanced in situ characterization techniques and theoretical calculation of metal–CO2 batteries are briefly introduced, and the combination of theory and experiment in the research of battery materials is discussed as well. Finally, the opportunities and key challenges of solid-state Na-CO2 electrochemical systems in the carbon-neutral era are presented

Effects of Mm(NiCoAlMn)_5 hydrogen storage alloy coated with Ni-Co-P alloy by electroless plating on electrochemical properties of hydride electrodes

The effect of chemical plating with Ni-Co-P alloy on the properties of MH electrodes is investigated. The results show that the efficiency of storage alloy and the activation of MH electrode have been improved by introducing 1.74% cobalt in the Ni-Co-P alloy coating. The initial discharge capacity is 208 mAh/g, The maximum discharge capacity gets to 298.5 mAh/g. At the same time the cycle life of MH electrodes is improved. The discharge capacity of MH electrodes coated with Ni-Co-P is 88% of the maximum discharge capacity after 300 cycles. Whereas the discharge capacity of bare alloy electrodes retains 62% of the maximum capacity after 300 cycles. An increment of discharge capacity is mainly due to the superposition of the oxidation current of Co as well as improved efficiency of microcurrent collection. The effect of Ni-Co-P alloy coating by electroless plating on the kinetic properties of hydride electrode has been systematically investigated by electrochemical techniques. The results indicate that the kinetic properties of MH electrodes, including exchange current density, limiting current density, have been improved markedly. This improvement of kinetic properties leads to the decrease of the overpotential of anodic and cathodic polarization