On-site monitoring and numerical simulation have been combined to analyze the stability of the jointed surrounding rock and the stress inside the lining structure of a sample deeply buried hydraulic tunnel.We show tha...On-site monitoring and numerical simulation have been combined to analyze the stability of the jointed surrounding rock and the stress inside the lining structure of a sample deeply buried hydraulic tunnel.We show that the deformation around the tunnel was mainly concentrated in the range 51.37 mm∼66.73 mm,the tunnel circumference was dominated by shear failure,and the maximum plastic zone was about 3.90 m.When the shotcrete treatment was performed immediately after the excavation,the deformation of the surrounding rock was reduced by 58.94%∼76.31%,and the extension of the plastic zone was relatively limited,thereby leading to improvements in terms of the stability of surrounding rock.When the support was provided at different time points,the stress of the surrounding rock in the shallow part of the tunnel was improved everywhere.In the tunnel section with high ground stress and joint development,when 10 cm steel fiber concrete spray layer and 40 cm C25 concrete secondary lining were used,the maximum tensile stress on the lining structure was 0.89 MPa,i.e.,it was less than the tensile strength of concrete,which indicates that the internal force of the lining can meet the overall requirements.展开更多
Water splitting is important to the conversion and storage of renewable energy,but slow kinetics of the oxygen evolution reaction(OER)greatly limits its utility.Here,under visible light illumination,the p-n WO_(3)/SnS...Water splitting is important to the conversion and storage of renewable energy,but slow kinetics of the oxygen evolution reaction(OER)greatly limits its utility.Here,under visible light illumination,the p-n WO_(3)/SnSe_(2)(WS)heterojunction significantly activates OER catalysis of CoFe-layered double hydroxide(CF)/carbon nanotubes(CNTs).Specifically,the catalyst achieves an overpotential of 224 mV at 10 mA cm^(-2)and a small Tafel slope of 47 mV dec^(-1),superior to RuO_(2)and most previously reported transition metal-based OER catalysts.The p-n WS heterojunction shows strong light absorption to produce photogenerated carriers.The photogenerated holes are trapped by CF to suppresses the charge recombination and facilitate charge transfer,which accelerates OER kinetics and boost the activity for the OER.This work highlights the possibility of using heterojunctions to activate OER catalysis and advances the design of energy-efficient catalysts for water oxidation systems using solar energy.展开更多
Since most electrocatalysts for oxygen evolution reaction(OER),except for precious metal oxides RuO_(2) and IrO_(2),are unstable in harsh acidic solutions,it is highly desirable to develop high-performance OER electro...Since most electrocatalysts for oxygen evolution reaction(OER),except for precious metal oxides RuO_(2) and IrO_(2),are unstable in harsh acidic solutions,it is highly desirable to develop high-performance OER electrocatalysts for acidic media,though it is still a big challenge.Herein,we report a simple strategy to produce carboxyl-enriched multiwalled carbon nanotubes(COOH-MWNTs)that exhibit stable and high electrocatalytic activities for OER in acidic solutions,showing an overpotential at a current density of 10 mA cm^(–2) and a Tafel slope as low as of 265 mV and 82 mV dec^(–1),respectively.As far as we are aware,these results represent the best OER performance for metal-free electrocatalysts,even comparable to those of RuO_(2) and IrO_(2).We have further revealed the catalytic mechanism,which involves one electron lose from the COOH-MWNTs catalyst at the beginning of the OER process to trigger H_(2)O molecule oxidation by forming peralcohol,followed by the recapture of one electron from water molecule to oxidize water and to recover the initial state for the COOH-MWNTs catalyst.The unravel of this new OER mechanism is important as it provides new insights into the crucial role of organic functional groups in electrocatalytic processes.Also,the mechanistic understanding can be used to guide the design and development of novel metalfree catalysts for acidic OER electrocatalysis and beyond.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51769031)Regional Innovation Guidance Plan Project of the XPCC(Grant No.2021BB004).
文摘On-site monitoring and numerical simulation have been combined to analyze the stability of the jointed surrounding rock and the stress inside the lining structure of a sample deeply buried hydraulic tunnel.We show that the deformation around the tunnel was mainly concentrated in the range 51.37 mm∼66.73 mm,the tunnel circumference was dominated by shear failure,and the maximum plastic zone was about 3.90 m.When the shotcrete treatment was performed immediately after the excavation,the deformation of the surrounding rock was reduced by 58.94%∼76.31%,and the extension of the plastic zone was relatively limited,thereby leading to improvements in terms of the stability of surrounding rock.When the support was provided at different time points,the stress of the surrounding rock in the shallow part of the tunnel was improved everywhere.In the tunnel section with high ground stress and joint development,when 10 cm steel fiber concrete spray layer and 40 cm C25 concrete secondary lining were used,the maximum tensile stress on the lining structure was 0.89 MPa,i.e.,it was less than the tensile strength of concrete,which indicates that the internal force of the lining can meet the overall requirements.
基金the National Natural Science Foundation of China(No.41807213)the Hydrogeo-logical Survey Project of Huangshui River(No.DD20190331).
文摘Water splitting is important to the conversion and storage of renewable energy,but slow kinetics of the oxygen evolution reaction(OER)greatly limits its utility.Here,under visible light illumination,the p-n WO_(3)/SnSe_(2)(WS)heterojunction significantly activates OER catalysis of CoFe-layered double hydroxide(CF)/carbon nanotubes(CNTs).Specifically,the catalyst achieves an overpotential of 224 mV at 10 mA cm^(-2)and a small Tafel slope of 47 mV dec^(-1),superior to RuO_(2)and most previously reported transition metal-based OER catalysts.The p-n WS heterojunction shows strong light absorption to produce photogenerated carriers.The photogenerated holes are trapped by CF to suppresses the charge recombination and facilitate charge transfer,which accelerates OER kinetics and boost the activity for the OER.This work highlights the possibility of using heterojunctions to activate OER catalysis and advances the design of energy-efficient catalysts for water oxidation systems using solar energy.
基金support from the Hydrogeological Survey Project of Huangshui River(No.DD20190331)We are also grateful for the partial support by Australian Research Council(DP 190103881 and FL 190100126).
文摘Since most electrocatalysts for oxygen evolution reaction(OER),except for precious metal oxides RuO_(2) and IrO_(2),are unstable in harsh acidic solutions,it is highly desirable to develop high-performance OER electrocatalysts for acidic media,though it is still a big challenge.Herein,we report a simple strategy to produce carboxyl-enriched multiwalled carbon nanotubes(COOH-MWNTs)that exhibit stable and high electrocatalytic activities for OER in acidic solutions,showing an overpotential at a current density of 10 mA cm^(–2) and a Tafel slope as low as of 265 mV and 82 mV dec^(–1),respectively.As far as we are aware,these results represent the best OER performance for metal-free electrocatalysts,even comparable to those of RuO_(2) and IrO_(2).We have further revealed the catalytic mechanism,which involves one electron lose from the COOH-MWNTs catalyst at the beginning of the OER process to trigger H_(2)O molecule oxidation by forming peralcohol,followed by the recapture of one electron from water molecule to oxidize water and to recover the initial state for the COOH-MWNTs catalyst.The unravel of this new OER mechanism is important as it provides new insights into the crucial role of organic functional groups in electrocatalytic processes.Also,the mechanistic understanding can be used to guide the design and development of novel metalfree catalysts for acidic OER electrocatalysis and beyond.
