The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into ...The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N4-C)configuration to obtain Ni-X-N3-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N3-C(X:S,Se,and Te)SACs,Ni-Se-N3-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98%at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2)battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N3-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of*COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.展开更多
For an energy transfer network, the irreversible depletion of excited electron energy occurs through either an efficient flow into an outer energy sink or an inefficient decay. With a small decay rate, the energy tran...For an energy transfer network, the irreversible depletion of excited electron energy occurs through either an efficient flow into an outer energy sink or an inefficient decay. With a small decay rate, the energy transfer efficiency is quantitatively reflected by the average life time of excitation energy before being trapped in the sink where the decay process is omitted. In the weak dissipation regime, the trapping time is analyzed within the exciton population subspace based on the secular Redfield equation. The requirement of the noise-enhanced energy transfer is obtained, where the trapping time follows an exact or approximate 1/F- scaling of the dissipation strength F. On the opposite side, optimal initial system states are conceptually constructed to suppress the 1/F-scaling of the trapping time and maximize the coherent transfer efficiency. Our theory is numerically testified in four models, including a biased two-site system, a symmetric three-site branching system, a homogeneous one- dimensional chain, and an 8-chromophore FMO protein complex.展开更多
this work,the polarization effects of a strongly magnetized quark-gluon plasma are studied at finite temperature.It is found that a background magnetic field can have a strong effect on the photon and dilepton emissio...this work,the polarization effects of a strongly magnetized quark-gluon plasma are studied at finite temperature.It is found that a background magnetic field can have a strong effect on the photon and dilepton emission rates.It affects not only the total rate but also the angular dependence.In particular,the Landau-level quantization leads to a nontrivial momentum dependence of the photon/dilepton anisotropic flow coefficient on transverse momentum.In the case of photon emission,nonzero coefficients v_(n)(with even n)have opposite signs at small and large values of the transverse momentum.Additionally,the v_(n) signs alternate with increasing vn,and their approximate values decrease as 1/n^(2) in magnitude.The anisotropy of dilepton emission is well-pronounced only at large transverse momenta and small invariant masses.The corresponding Un coefficients are of the same magnitude and show a similar sign-alternative pattern with increasing n as in the photon emission.It is proposed that the anisotropy of the photon and dilepton emission may serve as indirect measurements of the magnetic field.展开更多
文摘The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N4-C)configuration to obtain Ni-X-N3-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N3-C(X:S,Se,and Te)SACs,Ni-Se-N3-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98%at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2)battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N3-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of*COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.
基金supported by the National Natural Science Foundation of China(No.21573195)the Ministry of Science and Technology of China(MOST-2014CB921203)
文摘For an energy transfer network, the irreversible depletion of excited electron energy occurs through either an efficient flow into an outer energy sink or an inefficient decay. With a small decay rate, the energy transfer efficiency is quantitatively reflected by the average life time of excitation energy before being trapped in the sink where the decay process is omitted. In the weak dissipation regime, the trapping time is analyzed within the exciton population subspace based on the secular Redfield equation. The requirement of the noise-enhanced energy transfer is obtained, where the trapping time follows an exact or approximate 1/F- scaling of the dissipation strength F. On the opposite side, optimal initial system states are conceptually constructed to suppress the 1/F-scaling of the trapping time and maximize the coherent transfer efficiency. Our theory is numerically testified in four models, including a biased two-site system, a symmetric three-site branching system, a homogeneous one- dimensional chain, and an 8-chromophore FMO protein complex.
文摘this work,the polarization effects of a strongly magnetized quark-gluon plasma are studied at finite temperature.It is found that a background magnetic field can have a strong effect on the photon and dilepton emission rates.It affects not only the total rate but also the angular dependence.In particular,the Landau-level quantization leads to a nontrivial momentum dependence of the photon/dilepton anisotropic flow coefficient on transverse momentum.In the case of photon emission,nonzero coefficients v_(n)(with even n)have opposite signs at small and large values of the transverse momentum.Additionally,the v_(n) signs alternate with increasing vn,and their approximate values decrease as 1/n^(2) in magnitude.The anisotropy of dilepton emission is well-pronounced only at large transverse momenta and small invariant masses.The corresponding Un coefficients are of the same magnitude and show a similar sign-alternative pattern with increasing n as in the photon emission.It is proposed that the anisotropy of the photon and dilepton emission may serve as indirect measurements of the magnetic field.
