Chubin Wan

Rodlike CeO2/carbon nanocomposite derived from metal–organic frameworks for enhanced supercapacitor applications

The rod-shaped CeO2@C architectures have been synthesized by novel and facile methods initially from metal–organic frameworks (MOFs). The MOF-derived material showed a pseudocapacitance of 1102 F g−1 at 2 A g−1 and 418 F g−1 at a high current density of 20 A g−1 and had excellent cyclic stability of about 2.3% decrease after 5000 cycles. Results revealed that favorable effects of dispersed partially graphitic carbon in the CeO2@C composite could improve electronic conductivity, which made this product be an alternative high-performance electrode for supercapacitors.

Energetics of He and H Atoms in W–Ta Alloys: First-Principle Calculations

Properties of various defects of He and H atoms in W?Ta alloys are investigated based on density functional theory. The tetrahedral interstitial site is the most configured site for self-interstitial He and H in W and W?Ta alloys. Only a single He atom favors a substitutional site in the presence of a nearby vacancy. However, in the coexistence of He and H atoms in the presence of the vacancy, the single H atom favors the tetrahedral interstitial site (TIS) closest to the vacancy, and the He atom takes the vacancy center. The addition of Ta can reduce the formation energy of TIS He or H defects. The substituted Ta affects the charge density distribution in the vicinity of the He atom and decreases the valence electron density of the H atoms. A strong hybridization of the H s states and the nearest W d state s exists in W 53 He 1 H 1 structure. The sequence of the He p projected DOS at the Fermi energy level is in agreement with the order of the formation energy of the He?H pair in the systems.

Clustering and Dissolution of Small Helium Clusters in Bulk Tungsten

Density functional theory calculations are conducted to investigate the stability and interactions among small helium (He) clusters in bulk tungsten (W). The lowest energy structure of each cluster for sizes n = 1 to 6 is determined. With the formation of He clusters, He defects form in bulk W. The thermodynamics of the clusters are investigated in the temperature range of 1000–2300K using molecular dynamics. This study provides the information essential to understand small He cluster behavior in bulk W.

Synergistic effect of Li–Ti and K–Ti co-doping on the dehydrogenation properties of NaAlH4: an ab initio study

The synergistic effect of Li–Ti and K–Ti dopants on the energy, structure and electronic properties of NaAlH4 has been investigated using density functional theory and ab initio molecular dynamics. Pair distribution functional analyses show that the substitution of NaAlH4 by Li2Ti and K2Ti favor not only the release of H2 but also the reductions in the barrier energies of (AlH4)− units. Density of states analyses suggest that the weakening of Al–H bonds in Li2Ti- and K2Ti-doped NaAlH4 is attributed to the formation of Ti–Al and Ti–H phases. Bader atomic charges analyses imply that the strong interaction of Li–Al prevent the further formation of Ti–Al clusters. The results of H removal energies analyses reveal that both Li2Ti and K2Ti are favorable catalysts for NaAlH4. Thus, that a Li2Ti dopant, with lighter weight than K2Ti, can be applied as a favorable catalyst for NaAlH4 has been given for the first time.