Electrochemical reduction of CO_(2)(CERR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation,and carbon recycles utilization.Conventional metal catalysts suffered from low durability and s...Electrochemical reduction of CO_(2)(CERR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation,and carbon recycles utilization.Conventional metal catalysts suffered from low durability and sluggish kinetics impede the practical application.On the other hand,doped carbon materials recently demonstrate superior catalytic performance in CERR,which shows the potential to diminish the problems of metal catalysts to some extent.Herein,we present the design and fabrication of nitrogen(N),phosphorus(P)co-doped metal-free carbon materials as an efficient and stable electrocatalyst for reduction of CO_(2) to CO,which exhibits an excellent performance with a high faradaic efficiency of 92%(-0.55 V vs.RHE)and up to 24 h stability.A series of characterizations including TEM and XPS verified that nitrogen and phosphorous are successfully incorporated into the carbon matrix.Moreover,the comparisons between co-doping and single doping catalysts reveal that co-doping can significantly increase CERR performance.The improved catalytic activity is attributed to the synergetic effects between nitrogen and phosphorous dopants,which effectively modulate properties of the active site.The density functional theory(DFT)calculations were also performed to understand the synergy effects of dopants.It is revealed that the phosphorous doping can significantly lower the Gibbs free energy of COOH^(*)formation.Moreover,the introduction of the second dopants phosphorous can reduce the reaction barrier along the reaction path and cause polarization of density of states at the Fermi level.These changes can greatly enhance the activity of the catalysts.From a combined experimental and computational exploration,current work provides valuable insights into the reaction mechanism of CERR on N,P co-doped carbon catalysts,and the influence from synergy effects between dopants,which paves the way for the rational design of novel metal-free catalysts for CO2 electro-reduction.展开更多
Li-S batteries have aroused intense interests as one of the most promising high-energy-density storage technology.However,the complex undesired shuttle effect induced by dissolution and diffusion of lithium polysulfid...Li-S batteries have aroused intense interests as one of the most promising high-energy-density storage technology.However,the complex undesired shuttle effect induced by dissolution and diffusion of lithium polysulfide intermediates remains the major setback of this technology.Chemical modification of carbon cathode through heteroatom-doping is widely accepted as an effective method to inhibit the shuttle effect in Li-S battery cathode.Herein,using first principle calculations,we systematically examined the interaction between halogenated graphene and lithium polysulfide species.It is found that the halogen dopants(F,Cl,Br,I)significantly modify the local electronic structure of adsorption site and further induce a polarization to trap the polysulfides.Interestingly,a concave curve is observed from F to I for lithium polysulfide adsorption rather than a linear relation.The exceptions demonstrated from iodine dopant is carefully analyzed and attributed to its unique charge state.Moreover,boron as second dopant further strengthens the interaction between halogenated graphene and polysulfide molecule.Based on halogenation strategy,lithium polysulfide/cathode interactions are tuned in a wide range,which can also be of great importance to accelerate redox reaction in Li-S battery.Overall,an effective method by halogenation is verified to regulate the adsorption of lithium polysulfide and also enhance the reaction kinetics of the Li-S battery system.展开更多
The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices,which can realize the processing of thick silicon structures.This paper proposes that indium tin oxides...The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices,which can realize the processing of thick silicon structures.This paper proposes that indium tin oxides(ITO)film can serve as a deep silicon etching cut-off layer because ITO is less damaged under the attack of fluoride ions.ITO has good electrical conductivity and can absorb fluoride ions for silicon etching and reduce the reflection of fluoride ions,thus reducing the foot effect.The removal and release of ITO use an acidic solution,which does not damage the silicon structure.Therefore,the selection of the sacrificial layer has an excellent effect in maintaining the shape of the MEMS structure.This method is used in the preparation of MEMS accelerometers with a structure thickness of 100μm and a feature size of 4μm.The over-etching of the bottom of the silicon structure caused by the foot effect is negligible.The difference between the simulated value and the designed value of the device characteristic frequency is less than 5%.This indicates that ITO is an excellent deep silicon etch stopper material.展开更多
Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the me...Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes, and analyzed the effect of the parasitic charge on the output stability. This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes. Due to the DC voltage required for the electrostatic actuation, the parasitic charge in the dielectric layer would accumulate and induce a residual voltage. This voltage had an impact on the resonant frequency of the gyroscopes, so as to affect the output stability. The theoretical studies were also confirmed by our experimental results. It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.展开更多
基金supported by the National Natural Science Foundation of China(21573255,21573062)Natural Science Foundation of Liao Ning Province(20180510014)+1 种基金supported by Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science and the State Key Laboratory of Catalytic Materials and Reaction Engineering(RIPP,SINOPEC)supported by the Special Program for Applied Research on Super Computation of the NSFC Guangdong Joint Fund(the second phase)under Grant No.U1501501。
文摘Electrochemical reduction of CO_(2)(CERR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation,and carbon recycles utilization.Conventional metal catalysts suffered from low durability and sluggish kinetics impede the practical application.On the other hand,doped carbon materials recently demonstrate superior catalytic performance in CERR,which shows the potential to diminish the problems of metal catalysts to some extent.Herein,we present the design and fabrication of nitrogen(N),phosphorus(P)co-doped metal-free carbon materials as an efficient and stable electrocatalyst for reduction of CO_(2) to CO,which exhibits an excellent performance with a high faradaic efficiency of 92%(-0.55 V vs.RHE)and up to 24 h stability.A series of characterizations including TEM and XPS verified that nitrogen and phosphorous are successfully incorporated into the carbon matrix.Moreover,the comparisons between co-doping and single doping catalysts reveal that co-doping can significantly increase CERR performance.The improved catalytic activity is attributed to the synergetic effects between nitrogen and phosphorous dopants,which effectively modulate properties of the active site.The density functional theory(DFT)calculations were also performed to understand the synergy effects of dopants.It is revealed that the phosphorous doping can significantly lower the Gibbs free energy of COOH^(*)formation.Moreover,the introduction of the second dopants phosphorous can reduce the reaction barrier along the reaction path and cause polarization of density of states at the Fermi level.These changes can greatly enhance the activity of the catalysts.From a combined experimental and computational exploration,current work provides valuable insights into the reaction mechanism of CERR on N,P co-doped carbon catalysts,and the influence from synergy effects between dopants,which paves the way for the rational design of novel metal-free catalysts for CO2 electro-reduction.
基金supported by the NSFC(21573255)the Natural Science Foundation of Liaoning Province(20180510014)+1 种基金supported Joint Research Fund Liaoning Shenyang National Laboratory for Materials Science and the State Key Laboratory of Catalytic Materials and Reaction Engineering(RIPP,SINOPEC)supported by the Special Program for Applied Research on Super Computation of the NSFC Guangdong Joint Fund(the second phase)under Grant no.U1501501。
文摘Li-S batteries have aroused intense interests as one of the most promising high-energy-density storage technology.However,the complex undesired shuttle effect induced by dissolution and diffusion of lithium polysulfide intermediates remains the major setback of this technology.Chemical modification of carbon cathode through heteroatom-doping is widely accepted as an effective method to inhibit the shuttle effect in Li-S battery cathode.Herein,using first principle calculations,we systematically examined the interaction between halogenated graphene and lithium polysulfide species.It is found that the halogen dopants(F,Cl,Br,I)significantly modify the local electronic structure of adsorption site and further induce a polarization to trap the polysulfides.Interestingly,a concave curve is observed from F to I for lithium polysulfide adsorption rather than a linear relation.The exceptions demonstrated from iodine dopant is carefully analyzed and attributed to its unique charge state.Moreover,boron as second dopant further strengthens the interaction between halogenated graphene and polysulfide molecule.Based on halogenation strategy,lithium polysulfide/cathode interactions are tuned in a wide range,which can also be of great importance to accelerate redox reaction in Li-S battery.Overall,an effective method by halogenation is verified to regulate the adsorption of lithium polysulfide and also enhance the reaction kinetics of the Li-S battery system.
基金the Laboratory Open Fund of Beijing Smart-chip Microelectronics Technology Co.,Ltd and Chinese National Science Foundation(Contract No.52075519 and 61974136).
文摘The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices,which can realize the processing of thick silicon structures.This paper proposes that indium tin oxides(ITO)film can serve as a deep silicon etching cut-off layer because ITO is less damaged under the attack of fluoride ions.ITO has good electrical conductivity and can absorb fluoride ions for silicon etching and reduce the reflection of fluoride ions,thus reducing the foot effect.The removal and release of ITO use an acidic solution,which does not damage the silicon structure.Therefore,the selection of the sacrificial layer has an excellent effect in maintaining the shape of the MEMS structure.This method is used in the preparation of MEMS accelerometers with a structure thickness of 100μm and a feature size of 4μm.The over-etching of the bottom of the silicon structure caused by the foot effect is negligible.The difference between the simulated value and the designed value of the device characteristic frequency is less than 5%.This indicates that ITO is an excellent deep silicon etch stopper material.
基金supported by the National Natural Science Foundation of China(No.61504130)
文摘Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes, and analyzed the effect of the parasitic charge on the output stability. This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes. Due to the DC voltage required for the electrostatic actuation, the parasitic charge in the dielectric layer would accumulate and induce a residual voltage. This voltage had an impact on the resonant frequency of the gyroscopes, so as to affect the output stability. The theoretical studies were also confirmed by our experimental results. It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.
