Hui Wang

Role of different coordinated Cu and reactive oxygen species on the highly active Cu–Ce–Zr mixed oxides in NH3-SCO: a combined in situ EPR and O2-TPD approach

Novel Cu–Ce–Zr mixed oxides were synthesized by a citric acid sol–gel method, and they exhibited an excellent NH3-SCO activity (180 °C, TOF = 1.33 h−1). The finely dispersed CuO, Cu–Ce–Zr solid solution and monomeric Cu2+ ions in octahedral sites were the main active sites. The finely dispersed CuO species were the NH3 adsorption sites, and their adsorption capacity could be improved by their good reducibility. The Cu–Ce–Zr solid solution was an important intermediate in oxygen transfer from bulk to surface. In situ EPR analysis indicated that the isolated Cu2+ located in the octahedral sites was more active compared with that located in the square-planar pyramidal sites, and it induced the formation of more Cu–Ce–Zr solid solution. Meanwhile, the in situ O2-TPD results showed that both adsorbed oxygen and bulk lattice oxygen were the active oxygen adspecies, and the adsorbed oxygen molecules were more active than the bulk lattice oxygen in NH3 oxidation.

Error-field penetration in reversed magnetic shear configurations

Error-field penetration in reversed magnetic shear (RMS) configurations is numerically investigated by using a two-dimensional resistive magnetohydrodynamic model in slab geometry. To explore different dynamic processes in locked modes, three equilibrium states are adopted. Stable, marginal, and unstable current profiles for double tearing modes are designed by varying the current intensity between two resonant surfaces separated by a certain distance. Further, the dynamic characteristics of locked modes in the three RMS states are identified, and the relevant physics mechanisms are elucidated. The scaling behavior of critical perturbation value with initial plasma velocity is numerically obtained, which obeys previously established relevant analytical theory in the viscoresistive regime.