Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and...Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and optimal adsorption sites,the hollow(H)sites were finally identified as favorable dissociation sites for N_(2).The dissociation barriers of N_(2)are 0.87eV on Ir(100)and 1.12eV on Ir(110),which can be overcome at around 348 and 448 K,respectively.Therefore,Ir(100)is screened as a promising catalyst for N_(2)dissociation compared to Ir(110).This can be attributed to the significantly higher adsorption energy of N_(2)on the H site of Ir(100)(−0.48 eV)compared to that on Ir(110)(−0.22 eV),leading to different dissociation mechanisms on Ir(100)and Ir(110).Ir(100)can dissociate N_(2)directly on H site and Ir(110)should firstly capture N_(2)via bridge site and further transfer the adsorbed N_(2)to the H site,which will dramatically deteriorate the reactivity of N_(2)dissociation.In addition,the following protonation processes of dissociated∗N atoms are all exothermal at 348 K on Ir(100),indicating that the ammonia synthesis can occur spontaneously as the temperature higher than 348 K.These results have provided a reasonable materials design scheme for subsequent ammonia synthesis.展开更多
Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with th...Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with the continuous development of material systems and modification strategies,researchers have gradually found that D-band center theory is usually effective for large metal particle systems,but for small metal particle systems or semiconductors,such as single atom systems,the opposite conclusion to the D-band center theory is often obtained.To solve the issue above,here we propose a bonding and anti-bonding orbitals stable electron intensity difference(BASED)theory for surface chemistry.The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory,but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites.Importantly,a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory,where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5Å.In short,the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.展开更多
We designed and fabricated a smart microcavity sensor with a vertically coupled structure on the end face of a multi-core fiber using two-photon lithography technology. The influence of gap in vertical coupling struct...We designed and fabricated a smart microcavity sensor with a vertically coupled structure on the end face of a multi-core fiber using two-photon lithography technology. The influence of gap in vertical coupling structure on the resonance characteristics of bonding and anti-bonding modes in the transmission spectrum was studied through simulation and experiments. The results indicate that the bonding and anti-bonding modes generated by the vertical coupling of the two microcavities, as well as the changes in the radius and refractive index of the micro-toroid, and the distance between the microcavities caused by the absorption of vapor during the gas sensing process, exhibit different wavelength shifts for the two resonant modes. Smart microcavity sensors exhibit sensitivity and sensing characteristics. .展开更多
基金funded by the Natural Science Foundation of China(No.21603109)the Henan Joint Fund of the National Natural Science Foundation of China(No.U1404216)+1 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0676)supported by Natural Science Basic Research Program of Shanxi(Nos.2022JQ-108,2022JQ096)。
文摘Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and optimal adsorption sites,the hollow(H)sites were finally identified as favorable dissociation sites for N_(2).The dissociation barriers of N_(2)are 0.87eV on Ir(100)and 1.12eV on Ir(110),which can be overcome at around 348 and 448 K,respectively.Therefore,Ir(100)is screened as a promising catalyst for N_(2)dissociation compared to Ir(110).This can be attributed to the significantly higher adsorption energy of N_(2)on the H site of Ir(100)(−0.48 eV)compared to that on Ir(110)(−0.22 eV),leading to different dissociation mechanisms on Ir(100)and Ir(110).Ir(100)can dissociate N_(2)directly on H site and Ir(110)should firstly capture N_(2)via bridge site and further transfer the adsorbed N_(2)to the H site,which will dramatically deteriorate the reactivity of N_(2)dissociation.In addition,the following protonation processes of dissociated∗N atoms are all exothermal at 348 K on Ir(100),indicating that the ammonia synthesis can occur spontaneously as the temperature higher than 348 K.These results have provided a reasonable materials design scheme for subsequent ammonia synthesis.
文摘Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with the continuous development of material systems and modification strategies,researchers have gradually found that D-band center theory is usually effective for large metal particle systems,but for small metal particle systems or semiconductors,such as single atom systems,the opposite conclusion to the D-band center theory is often obtained.To solve the issue above,here we propose a bonding and anti-bonding orbitals stable electron intensity difference(BASED)theory for surface chemistry.The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory,but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites.Importantly,a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory,where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5Å.In short,the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.
文摘We designed and fabricated a smart microcavity sensor with a vertically coupled structure on the end face of a multi-core fiber using two-photon lithography technology. The influence of gap in vertical coupling structure on the resonance characteristics of bonding and anti-bonding modes in the transmission spectrum was studied through simulation and experiments. The results indicate that the bonding and anti-bonding modes generated by the vertical coupling of the two microcavities, as well as the changes in the radius and refractive index of the micro-toroid, and the distance between the microcavities caused by the absorption of vapor during the gas sensing process, exhibit different wavelength shifts for the two resonant modes. Smart microcavity sensors exhibit sensitivity and sensing characteristics. .
