The rational design and synthesis of noble-metal-free electrocatalysts for water splitting is always important for the future hydrogen economy.Therefore,it is necessary to design an effective transition metal sulfide ...The rational design and synthesis of noble-metal-free electrocatalysts for water splitting is always important for the future hydrogen economy.Therefore,it is necessary to design an effective transition metal sulfide down to a molecular level.In this work,a multi-level spatial confinement strategy was developed to fabricate Co-promoted 1T-MoS_(2)(1T-Co-MoS_(2))by employing Evans-Showell-type polyoxometalates(POMs)[Co_(2)Mo_(10)O_(38)H_(4)]as molecular precursor.Highly dispersed 1T-Co-MoS_(2) nanoclusters with few layers(1-3 layers)and ultrasmall size(<5 nm)were synthesized within the hollow mesoporous carbon sphere(HMCS)by in situ vapor phase sulfurization.During the preparation,coordination bonds,organic cations and mesopores provide a triple-confinement environment to limit the growth of 1T-Co-MoS_(2) from the atomic level,molecular level to mesoscopic scale.The obtained 1T-Co-MoS_(2)@HMCS exhibits remarkable electrocatalytic activity and excellent long-term durability for hydrogen evolution reaction(HER),with overpotentials of 220 and 245 mV to achieve the current density of 200 mA cm^(-2) in 1 M KOH and 0.5 M H_(2)SO_(4),respectively.The corresponding theoretical calculations indicate that Co-S edge sites are the most active sites of 1T-Co-MoS_(2) for HER,reflecting the major significance of Co doping.The superior HER performance could be attributed to the high intrinsic activity from Co-doped 1T-MoS_(2) sites,abundant exposed active sites from ultra-dispersed nanosheets,and enhanced charge and mass transfer within the HMCS substrate.This work provides a novel design concept via hierarchical multiple-level confinement for the synthesis of high-quality 1T-Co-MoS_(2) and achieves outstanding performance in electrocatalytic HER.展开更多
In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conduct...In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conducted on EIMC mortar samples,and the physicomechanical properties were obtained.The effects of urea pre-hydrolysis time,mass ratio of liquid solution to magnesia,and urea concentration were analyzed.Experimental results indicated that the urea pre-hydrolysis based EIMC method had a better cementation ability of sandstone grain and greater crack surface bonding performance of sandstone than the existing microbial-induced magnesia carbonization(MIMC)method.The optimal bio-cementation conditions were of pre-hydrolysis time of 24 h,mass ratio of liquid solution to magnesia of 1.75,and urea concentration of 1 mol/L.Under these conditions,the peak tensile stress of EIMC mortar samples reached up to 948.45 kPa,and interfacial peak tensile stress of EIMC-sandstone samples reached 608.57 kPa.These values were 118.6%(799.97 kPa)and 123.2%(493.19 kPa)of those of samples bio-cemented by the MIMC method,respectively.The improved bio-cementation performance can be attributed to the pre-hydrolysis of urea,ensuring an adequate supply of CO_(3)^(2-) ions and promoting the magnesia hydration and the brucite carbonization.The increased production of hydrated magnesium carbonates,coupled with formation of the amorphous brucite facilitated by biomolecules,established a denser structure,enhancing the physicomechanical properties.Microcrack development near the interfacial zone of mortar and sandstone was an important factor in the reduced biocementation performance of the MIMC method.The EIMC method is a practical bio-healing method for rock weathering cracks due to the availability of urease and its good cementation properties.展开更多
基金supported by the National Natural Science Foundation of China(21878336,21805308)the Shandong Provincial Natural Science Foundation,China(ZR2018MB035)+1 种基金the Key Research and Development Project of Shandong Province(2019GSF109075)the Fundamental Research Funds for the Central Universities(20CX02213A),and the China University of Petroleum,Huadong(YCX2021153).
文摘The rational design and synthesis of noble-metal-free electrocatalysts for water splitting is always important for the future hydrogen economy.Therefore,it is necessary to design an effective transition metal sulfide down to a molecular level.In this work,a multi-level spatial confinement strategy was developed to fabricate Co-promoted 1T-MoS_(2)(1T-Co-MoS_(2))by employing Evans-Showell-type polyoxometalates(POMs)[Co_(2)Mo_(10)O_(38)H_(4)]as molecular precursor.Highly dispersed 1T-Co-MoS_(2) nanoclusters with few layers(1-3 layers)and ultrasmall size(<5 nm)were synthesized within the hollow mesoporous carbon sphere(HMCS)by in situ vapor phase sulfurization.During the preparation,coordination bonds,organic cations and mesopores provide a triple-confinement environment to limit the growth of 1T-Co-MoS_(2) from the atomic level,molecular level to mesoscopic scale.The obtained 1T-Co-MoS_(2)@HMCS exhibits remarkable electrocatalytic activity and excellent long-term durability for hydrogen evolution reaction(HER),with overpotentials of 220 and 245 mV to achieve the current density of 200 mA cm^(-2) in 1 M KOH and 0.5 M H_(2)SO_(4),respectively.The corresponding theoretical calculations indicate that Co-S edge sites are the most active sites of 1T-Co-MoS_(2) for HER,reflecting the major significance of Co doping.The superior HER performance could be attributed to the high intrinsic activity from Co-doped 1T-MoS_(2) sites,abundant exposed active sites from ultra-dispersed nanosheets,and enhanced charge and mass transfer within the HMCS substrate.This work provides a novel design concept via hierarchical multiple-level confinement for the synthesis of high-quality 1T-Co-MoS_(2) and achieves outstanding performance in electrocatalytic HER.
基金supported by the State Key Laboratory for Geo-Mechanics and Deep Underground Engineering,China University of Mining&Technology/China University of Mining&Technology,Beijing(Grant No.SKLGDUEK2214)the National Natural Science Foundation of China(Grant No.42477188)National Key Research and Development Program of China(Grant No.2023YFC3007102).
文摘In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conducted on EIMC mortar samples,and the physicomechanical properties were obtained.The effects of urea pre-hydrolysis time,mass ratio of liquid solution to magnesia,and urea concentration were analyzed.Experimental results indicated that the urea pre-hydrolysis based EIMC method had a better cementation ability of sandstone grain and greater crack surface bonding performance of sandstone than the existing microbial-induced magnesia carbonization(MIMC)method.The optimal bio-cementation conditions were of pre-hydrolysis time of 24 h,mass ratio of liquid solution to magnesia of 1.75,and urea concentration of 1 mol/L.Under these conditions,the peak tensile stress of EIMC mortar samples reached up to 948.45 kPa,and interfacial peak tensile stress of EIMC-sandstone samples reached 608.57 kPa.These values were 118.6%(799.97 kPa)and 123.2%(493.19 kPa)of those of samples bio-cemented by the MIMC method,respectively.The improved bio-cementation performance can be attributed to the pre-hydrolysis of urea,ensuring an adequate supply of CO_(3)^(2-) ions and promoting the magnesia hydration and the brucite carbonization.The increased production of hydrated magnesium carbonates,coupled with formation of the amorphous brucite facilitated by biomolecules,established a denser structure,enhancing the physicomechanical properties.Microcrack development near the interfacial zone of mortar and sandstone was an important factor in the reduced biocementation performance of the MIMC method.The EIMC method is a practical bio-healing method for rock weathering cracks due to the availability of urease and its good cementation properties.
基金supported by International Project of Science and Technology between South Africa and China's Mainland (2006DFB02480)key project of Hebei Natural Science Foundation of China (C2006000744)the project of Scientific and Technological Research and Development Hebei Province,China(07297162D)~~
