Doping Effects on the Reactivity of the MVO₅^– (M = V–Zn) Clusters in CO Oxidation Reaction

Abstract

Doped metal oxide catalysts have important applications in heterogeneous catalysis, whereas the fundamental effects of doping on the reactivity of catalysts are elusive. Herein, benefiting from the study of a series of atomic clusters MVO 5 − (M = V−Zn) in catalytic CO oxidation by molecular O 2 under thermal collision conditions, the crucial effects of doping on the electronic structure and then the catalytic reactivity of MVO 5 − were successfully rationalized by using mass spectrometry and theoretical calculations. We defined the energy gap of active orbitals that are closely related to electron transfer in MVO 5 − during CO oxidation. It was discovered that such an energy gap can modulate reaction thermodynamics, whereas the orbital overlap of MVO 5 − with CO controls the kinetics. The doped clusters MVO 5 − (M = Cr−Zn) have reduced energy gaps than that in host V 2 O 5 − , and doping can modify the orbital overlap of MVO 5 − (M = Cr−Zn) with CO. Only the MnVO 5 − and ZnVO 5 − clusters that have rational energy gaps and proper orbital overlap with CO are catalytically reactive.

Analysis of simple scattering models on the thermoelectric performance of analytical electron dispersions

“…While band structure models are commonly available or readily calculated -both analytical and numerically computed -it is generally more challenging to accurately capture the scattering time. Rigorously resolving the relaxation time τ (k) over the entire Brillouin zone is possible [8,[10][11][12][13][14][15][16][34][35][36][37][38][39], but computationally expensive, thus various approximations are commonly adopted. One of the most widespread approximations involves setting the scattering time to a constant, τ (k) = τ 0 (TAU model).…”

“…Rigorous first-principles calculations of electronphonon scattering have shown that often the scattering rates are (roughly) proportional to the electron DOS, D(E) [10,16,38,39]. Intuitively, one would expect the probability of scattering to scale with the number of available final states, which partially explains this trend.…”

“…∼ 10 k B T ). Concerning the scattering rates, rigorous DFT modeling of electron scattering has become more common in the past few years [8,[10][11][12][13][14][15][16][34][35][36][37][38][39], but these calculations are computationally intensive which hinders their routine usage. Most theoretical investigations rely on one of two simple scattering models: the constant relaxation-time approximation (referred to here as the TAU model) or the constant mean-free-path approximation (MFP model).…”

“…Recent first-principles calculations of electron-phonon scattering (the dominant intrinsic scattering mechanism in TE materials) have revealed that the scattering rates often display a trend that closely follows the electron density-of-states (DOS) [10,16,38,39], which is not as well captured within a constant scattering-time or meanfree-path assumption [16]. It can be shown that the scattering rates should have the same energy dependence as the DOS in the case of a 3D parabolic band with electronacoustic phonon scattering (within a deformation potential treatment) [40].…”

Unusual thermoelectric transport anisotropy in quasi-two-dimensional rhombohedral GeTe

“…Our rigorous el-ph scattering calculations show that, in the case of GeTe, both the scattering rates and MFP are energy-dependent. An alternative simple model, that appears to work well, assumes the scattering rate is proportional to the electron DOS [49,50].…”