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In order to solve the problems of vicious development of surrounding rock fissures, severe mining disturbance, weak bearing capacity of narrow coal pillar and damage and failure of roadway support system of gob-side entry driving with large section of large mining height in deep coal mine, taking the small coal pillar roadway excavation of 20203 working face of Dahaize Coal Mine as the engineering background, the internal and external stress field, limit equilibrium theory, numerical calculation simulation, engineering practice are used. It is comprehensively determined that the reasonable width of narrow coal pillar of gob-side entry driving with large section of 6.8 m mining height in deep coal mine is 6.5 m, and the surrounding rock comprehensive control technology of “high-strength concrete bedding + high prestressed bolt support of roadway sides + roof flexible bolt strong support + diamond metal mesh” is proposed. The research shows that: the width of internal stress field under this geological condition is 14.4 m, the width of coal pillar crushing area after mining previous working face is 3.1 m, and the reasonable width range of narrow coal pillar is 5.8 to 8.2 m; when the coal pillar size is 6.5 to 9.5 m, the stress of the coal pillar is improved, and the elastic zone appears above the coal pillar and the roadway roof, which can give full play to the anchoring effect of bolt (cable) to ensure the stability of the roof and sides; the convergence deformation of the roadway tends to be stable 32 days after the support is completed. The maximum deformation of the solid coal wall, coal pillar wall, solid coal side roof and coal pillar side roof are 52 mm, 60 mm, 62 mm and 67 mm respectively. During the mining of this working face, the overall deformation of the roadway is in a controllable range. The 6.5 m narrow coal pillar and comprehensive control technology of surrounding rock can realize the stable bearing of narrow coal pillar and long-term effective control of surrounding rock of gob-side driving with large section of large mining height in deep coal mine.

The exploration of clean, environmentally friendly, efficient and economical metal electrocatalysts is becoming more and more in-depth, but catalyst activity and stability are still the main goals. Herein, a thin regular pentagonal rough nanosheet array (La-CoNiOOH@FeSe@NiSe/NF) grown on a three-dimensional porous conductive surface was designed and synthesized. The prepared electrode material exhibited good catalytic activity in 1 M KOH solution, required only 270 mV of overpotential to provide 10 mA cm−2 current density for the oxygen evolution reaction (OER), and showed excellent stability for at least 90 hours during the OER process. The characterization test results proved that the incorporation of La changed the surface electronic structure, optimized the interface, modulated the active site on the surface of the material, and exposed a large number of active sites, thus improving the activity and stability of the catalyst material. At the same time, such a rough surface also gives the material excellent wettability and anti-bubble adhesion, which is also a key factor in maintaining the catalytic activity and OER stability of the material. This method provides a new idea for developing an efficient and economical electrolytic hydroelectricity catalyst. [ABSTRACT FROM AUTHOR]

It is necessary to explore new energy sources to alleviate the excessive demand for fossil energy. Water electrolysis is a promising means of sustainable hydrogen evolution. Herein, a Cu/NCF precursor was nitrized to prepare a nitrogen-doped carbon-coated multi-component NC@NiCoCu-N/NCF composite material. The good synergistic interactions among the three nitride phases, Cu3N, Ni4N, and Co2N, make H2O decomposition and H2 release more balanced during the reaction. The content and temperature were adjusted to explore the changes in the catalyst morphology and the trapezoidal nanosheets were transformed into a disordered rough coral-like nanostructure that facilitates better electrolyte penetration and provides more accessible active sites during the nitriding process. Nitrogen-doped carbon can enhance the conductivity of the catalyst, protecting the internal active structure from the erosion of the electrolyte and improving the structural stability. The NC@NiCoCu-N/NCF composite exhibited excellent hydrogen evolution performance and the overpotentials reached 89 mV and 131 mV under the current density of 10 mA cm−2 in 1.0 M KOH and 0.5 M H2SO4, respectively. Chronopotentiometry results indicated that the catalyst could operate continuously for at least 48 h and still maintain excellent structural stability. This study has great significance for the development of polymetallic or multicomponent catalysts designed to accelerate the field of hydrogen energy. [ABSTRACT FROM AUTHOR]

Rational design of cost-effective electrocatalysts with unique morphological structures and chemical compositions is highly imperative for the future hydrogen-based economy. Herein, we construct three-dimensional wrinkled Co-MoP/FeP4 nanospheres as hydrogen evolution reaction (HER) electrocatalysts by a simple and low-cost one-pot method. Due to the unique wrinkled nanosphere structure coupled with fine tuning of the electronic structure via Co doping and interactions between MoP/FeP4 heterostructures, the Co-MoP/FeP4 electrocatalyst delivers favorable HER activity: it requires only a low overpotential of 142 mV and 162 mV to achieve 10 mA cm−2 (Ej=10), respectively, in acidic and alkaline electrolytes, surpassing the MoP/FeP4 heterostructures (Ej=10 = 180 mV in acidic electrolyte; Ej=10 = 205 mV in alkaline electrolyte), and displays better stability and durability. This work introduces a facile and effective design principle that can finely adjust the morphology and electronic structure by an interfacial engineering strategy for highly active HER catalysts. [ABSTRACT FROM AUTHOR]

The construction of excellently performing electrocatalysts for hydrogen evolution reaction (HER) with a low-cost and economical strategy is still struggling with an enormous challenge in electrochemical water splitting. In this work, a novel N-doped porous carbon substrate constructed heterojunction electrocatalyst (MoS2-MoP/NC) was fabricated by a simple and facile method. Based on the electronic interaction and synergistic effect between MoS2 and MoP phases, the fabricated MoS2-MoP/NC heterojunction catalyst exhibited excellent electrocatalytic ability. In addition, the N-doped porous carbon substrate had a good charge/mass-transfer ability, which could effectively facilitate electronic transmission or prevent the aggregation of MoS2-MoP nanosheets and improve the catalytic activity. The heterojunction catalyst significantly improved HER activity with a low overpotential of 83 and 103 mV at 10 mA cm−2 in a 1.0 M KOH and 0.5 M H2SO4 and Tafel slope of 59.38 and 59.20 mV dec−1 for HER, respectively. This work provides a simple, less expensive and efficient approach for constructing high-performance heterojunction catalysts for HER. [ABSTRACT FROM AUTHOR]

Lithium-oxygen (Li-O2) batteries are receiving intense interest because of their high energy density. A new tubular δ-MnO2 material prepared by a simple hydrothermal synthesis is an efficient electrocatalyst for Li-O2 batteries. The synthesized δ-MnO2 exhibits a unique tubular structure, in which the porous walls are composed of highly dispersed ultrathin δ-MnO2 nanosheets. Such a unique structure and its intrinsic catalytic activity provide the right electrocatalyst characteristics for high-performance Li-O2 batteries. As a consequence, suppressed overpotentials-especially the oxygen evolution reaction overpotential-superior rate capability, and desirable cycle life are achieved with these submicron δ-MnO2 tubes as the electrocatalyst. Remarkably, the discharge product Li2O2 of the Li-O2 battery exhibits a uniform nanosheet-like morphology, which indicates the critical role of the δ-MnO2 in the electrochemical process, and a mechanism is proposed to analyze the catalysis of δ-MnO2. [ABSTRACT FROM AUTHOR]