A key challenge faced by organic electrodes is how to promote the redox reactions of functional groups to achieve high specific capacity and rate performance. Here, we report a two-dimensional (2D) microporous covalent-organic framework (COF), poly(imide-benzoquinone), via in situ polymerization on graphene (PIBN-G) to function as a cathode material for lithium-ion batteries (LIBs). Such a structure favors charge transfer from graphene to PIBN and full access of both electrons and Li ions to the abundant redox-active carbonyl groups, which are essential for battery reactions. This enables large reversible specific capacities of 271.0 and 193.1 mAh g at 0.1 and 10 C, respectively, and retention of more than 86 % after 300 cycles. The discharging/charging process successively involves 8 Li and 2 Li in the carbonyl groups of the respective imide and quinone groups. The structural merits of PIBN-G will trigger more investigations into the designable and versatile COFs for electrochemistry.

No abstract

Dissociation and energy transfer in high-energy collisions of O2 playimportant roles in simulating thermal energy content and heat flux in flows around hypersonicvehicles. Furthermore, atomic oxygen reactions on the vehicle surface are an importantcontributor to heat shield erosion. Molecular dynamics modeling is needed to better understandthe relevant rate processes. Because it is necessary to model the gas flows in high-temperatureshock waves, electronically excited states of O2 and O can be populated, and molecular dynamicssimulations should include collisions of electronically excited species and electronicallynonadiabatic collisions. This requires potential energy surfaces and state couplings for many energetically accessible electronic states. Here we report a systematic strategy to calculate such surfaces and couplings. We have applied this method to the fourteen lowest-energy potential energy surfaces in the 3A′ manifold of O3, and we report a neural-network fit to diabatic potential energy matrix (DPEM). We illustrate the use of the resulting DPEM by carrying out semiclassical dynamics calculations of cross sections for excitation of O2 inat two collision energies; these dynamics calculations are carried out by the 3A′ collisions with Ocurvature-driven coherent switching with decay of mixing method.

Cerium (Ce) plays important roles in catalysis. Its position in the sixth period of the periodic table leads to spin−orbit coupling (SOC) and other open-shell effects that make the quantum mechanical calculation of cerium compounds challenging. In this work, we investigated the low-lying spin states of Ce + and the bond energy of CeH + , both by multiconfigurational methods, in particular, SA-CASSCF, MC-PDFT, CASPT2, XMS-PDFT, and XMS-CASPT2, and by single-configurational methods, namely, Hartree−Fock theory and unrestricted Kohn−Sham density functional theory with 34 choices of the exchange−correlation functional. We found that only CASPT2, XMS-CASPT2, and SA-CASSCF (among the five multiconfigurational methods) and GAM, HCTH, SOGGA11, and OreLYP (among the 35 single-configuration methods) successfully predict that the SOC-free ground spin state of Ce + is a doublet state, and CASPT2 and GAM give the most accurate multireference and single-reference calculations, respectively, of the excitation energy of the first SOC-free excited state for Ce + . We calculated that the ground doublet state of Ce + is an intra-atomic hyper-open-shell state. We calculated the spin−orbit energy (E SO ) of Ce + by the five multiconfigurational methods and found that E SO calculated by CASPT2 is the closest to the experimental value. Taking advantage of the availability of an experimental D 0 for CeH + as a way to provide a unique test of theory, we showed that all the multiconfigurational methods overestimate D 0 by at least 246 meV (5.7 kcal/mol), and only three functionals, namely, SOGGA, MN15, and GAM, have an error of D 0 that is less than 200 meV (5 kcal/mol).

MC-PDFT can give the most accurate excitation energies for both valence and Rydberg states of 1,4-cyclohexadiene and 1,3-cyclohexadiene when the active space includes Rydberg orbitals.