The existence of multiple vacancies leads to significant changes in the local atomic structure,which can regulate the electronic structure of the surface and form unsaturated coordination geometries.However,the curren...The existence of multiple vacancies leads to significant changes in the local atomic structure,which can regulate the electronic structure of the surface and form unsaturated coordination geometries.However,the current methods employed to generate multiple vacancies in two-dimensional(2D)layered double hydroxide(LDH)materials are still difficult to achieve to some extent and are primarily limited to monolayer LDH structures.Here,we present an improved method to synthesize NiMoP/Ni_(2)P catalysts with a sponge-like porous structure.Firstly,NiO with dual defects was constructed by subjecting NiMo-LDH/Ni to air calcination.Subsequently,we performed phosphorization treatment and introduced multiple Ni vacancies and O vacancies as defect sites to tune the edge and substrate surfaces of LDH.At the same time,the electronic structure was tuned by adding P heteroatoms.The synergistic effect of porous structure,heterogeneous interfaces,vacancies,doping defects,and amorphous states can greatly enhance the electron transfer effect inside the catalysts,which significantly improves the catalytic ability of the oxygen evolution reaction(OER).Therefore,the overpotential for the oxygen evolution reaction of NiMoP/Ni_(2)P heterointerfaces reaches 270 mV at a current density of 10 mA·cm^(-2)under alkaline conditions,with the catalysts capable of sustaining high current densities even after the durability testing for 35 h.展开更多
Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated...Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.展开更多
A set of seven single junction thermal converter Micropotentiometers (μPots) has been constructed at the National Institute for Standards (NIS), Egypt. This set has been built to cover the low ac voltage ranges from ...A set of seven single junction thermal converter Micropotentiometers (μPots) has been constructed at the National Institute for Standards (NIS), Egypt. This set has been built to cover the low ac voltage ranges from 2 mV to 200 mV at frequencies from 40 Hz up to 20 kHz. The construction of the μPots set has been presented and an adopted calibration method has been performed as well. This method has been performed by means of a step-down procedure using a Digital Multi-Meter (DMM). The scaling procedures have been carried out in sequential steps starting from the calibration of the 200 mV-μpot by using DMM that is accurately calibrated at its 200 mV ac voltage range down to 2 mV-μPot. Furthermore, a new automatic calibration system has been established to achieve the scaling procedures. This system has been specially designed using Laboratory Virtual Instrument Engineering Workbench (LabVIEW) software to overcome the deficiencies of manual methods. The automatic calibration has been investigated of all mPots at different frequencies. The ac-dc differences for the μPots and their uncertainty evaluation from 2 mV to 200 mV at different frequencies from 40 Hz to 20 kHz have been determined.展开更多
Due to unique electrical properties and high catalytic efficiency,transition metal nitrogen-codoped car-bide(TM-N-C)has attracted tremendous interest as a multifunctional electrocatalyst for water splitting.Unlike tra...Due to unique electrical properties and high catalytic efficiency,transition metal nitrogen-codoped car-bide(TM-N-C)has attracted tremendous interest as a multifunctional electrocatalyst for water splitting.Unlike traditional single-source modification,herein a novel pomegranate-like high-entropy(HE)elec-trocatalyst of Ni_(3)ZnC_(0.7)decorated with homogeneous multimetal(Fe,Co,Cu,and Ni)nitrogen-codoped carbon matrix(Ni_(3)ZnC_(0.7)@CoNiCuFe-NC)is reported.It can be implemented by the simple thermal an-nealing method of multimetal codoped zeolitic imidazolate framework(ZIF).Benefiting from the syn-ergistic effects of plentiful TM-N-C species,template effect of ZIF and distinct nanoporous structure,HE electrocatalyst Ni_(3)ZnC_(0.7)@CoNiCuFe-NC exhibits outstanding electrocatalytic performance.When ap-plied in strong alkaline electrolyte(1.0 M KOH),the overpotentials of Ni_(3)ZnC_(0.7)@CoNiCuFe-NC present as low as 202 and 97 mV for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)at 10 mA cm^(−2)current density.Surprisingly as a bifunctional electrode,it can achieve the low cell voltage of 1.53 V at 10 mA cm^(−2)current density for overall water splitting,which is comparable to conventional IrO_(2)||Pt/C electrode and superior to the recently reported analogous bifunctional catalysts.Thus,the work proposes the direction for the rational design of homogeneous distribution of TM-N-C material for water splitting in the green hydrogen energy industry.展开更多
The paper expounds the metallogenic characterist ic s of Jiawula multimetals deposit in China and Uran multimetals deposit in Mongol ia. Comparative study shows that both deposits are volcanic hydrothermal mineral iza...The paper expounds the metallogenic characterist ic s of Jiawula multimetals deposit in China and Uran multimetals deposit in Mongol ia. Comparative study shows that both deposits are volcanic hydrothermal mineral ization with same epoch(Mesozoic), same source, same temperature, and same miner al assemblage, but volcanic structure are different. Therefore, both deposits ca n draw on experience of each other and supplement in future of second time ore- prospecting, and point out the new direction of ore-prospecting.展开更多
基金supported by the National Natural Science Foundation of China(No.22269010)Jiangxi Provincial Natural Science Foundation(No.20224BAB214021)the Opening Project of National Engineering Research Center for Domestic&Building Ceramics(No.GXZX2302).
文摘The existence of multiple vacancies leads to significant changes in the local atomic structure,which can regulate the electronic structure of the surface and form unsaturated coordination geometries.However,the current methods employed to generate multiple vacancies in two-dimensional(2D)layered double hydroxide(LDH)materials are still difficult to achieve to some extent and are primarily limited to monolayer LDH structures.Here,we present an improved method to synthesize NiMoP/Ni_(2)P catalysts with a sponge-like porous structure.Firstly,NiO with dual defects was constructed by subjecting NiMo-LDH/Ni to air calcination.Subsequently,we performed phosphorization treatment and introduced multiple Ni vacancies and O vacancies as defect sites to tune the edge and substrate surfaces of LDH.At the same time,the electronic structure was tuned by adding P heteroatoms.The synergistic effect of porous structure,heterogeneous interfaces,vacancies,doping defects,and amorphous states can greatly enhance the electron transfer effect inside the catalysts,which significantly improves the catalytic ability of the oxygen evolution reaction(OER).Therefore,the overpotential for the oxygen evolution reaction of NiMoP/Ni_(2)P heterointerfaces reaches 270 mV at a current density of 10 mA·cm^(-2)under alkaline conditions,with the catalysts capable of sustaining high current densities even after the durability testing for 35 h.
基金financial support from the SERB-SURE under file number of SUR/2022/003129Jong Hyeok Park acknowledges the support of the National Research Foundation of Korea (NRF)funded by the Ministry of Science and ICT (RS-2023-00302697,RS-2023-00268523).
文摘Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.
文摘A set of seven single junction thermal converter Micropotentiometers (μPots) has been constructed at the National Institute for Standards (NIS), Egypt. This set has been built to cover the low ac voltage ranges from 2 mV to 200 mV at frequencies from 40 Hz up to 20 kHz. The construction of the μPots set has been presented and an adopted calibration method has been performed as well. This method has been performed by means of a step-down procedure using a Digital Multi-Meter (DMM). The scaling procedures have been carried out in sequential steps starting from the calibration of the 200 mV-μpot by using DMM that is accurately calibrated at its 200 mV ac voltage range down to 2 mV-μPot. Furthermore, a new automatic calibration system has been established to achieve the scaling procedures. This system has been specially designed using Laboratory Virtual Instrument Engineering Workbench (LabVIEW) software to overcome the deficiencies of manual methods. The automatic calibration has been investigated of all mPots at different frequencies. The ac-dc differences for the μPots and their uncertainty evaluation from 2 mV to 200 mV at different frequencies from 40 Hz to 20 kHz have been determined.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.22008180 and 21878231)the Natural Science Foundation of Tianjin(Nos.19JCQNJC05700 and 19JCZDJC37300)the Tianjin College Student Innovation and Entrepreneurship Training Program(No.202010058034).This work was also supported by the Analytical&Testing Center of Tiangong University for structural characterization tests.
文摘Due to unique electrical properties and high catalytic efficiency,transition metal nitrogen-codoped car-bide(TM-N-C)has attracted tremendous interest as a multifunctional electrocatalyst for water splitting.Unlike traditional single-source modification,herein a novel pomegranate-like high-entropy(HE)elec-trocatalyst of Ni_(3)ZnC_(0.7)decorated with homogeneous multimetal(Fe,Co,Cu,and Ni)nitrogen-codoped carbon matrix(Ni_(3)ZnC_(0.7)@CoNiCuFe-NC)is reported.It can be implemented by the simple thermal an-nealing method of multimetal codoped zeolitic imidazolate framework(ZIF).Benefiting from the syn-ergistic effects of plentiful TM-N-C species,template effect of ZIF and distinct nanoporous structure,HE electrocatalyst Ni_(3)ZnC_(0.7)@CoNiCuFe-NC exhibits outstanding electrocatalytic performance.When ap-plied in strong alkaline electrolyte(1.0 M KOH),the overpotentials of Ni_(3)ZnC_(0.7)@CoNiCuFe-NC present as low as 202 and 97 mV for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)at 10 mA cm^(−2)current density.Surprisingly as a bifunctional electrode,it can achieve the low cell voltage of 1.53 V at 10 mA cm^(−2)current density for overall water splitting,which is comparable to conventional IrO_(2)||Pt/C electrode and superior to the recently reported analogous bifunctional catalysts.Thus,the work proposes the direction for the rational design of homogeneous distribution of TM-N-C material for water splitting in the green hydrogen energy industry.
文摘The paper expounds the metallogenic characterist ic s of Jiawula multimetals deposit in China and Uran multimetals deposit in Mongol ia. Comparative study shows that both deposits are volcanic hydrothermal mineral ization with same epoch(Mesozoic), same source, same temperature, and same miner al assemblage, but volcanic structure are different. Therefore, both deposits ca n draw on experience of each other and supplement in future of second time ore- prospecting, and point out the new direction of ore-prospecting.
