2018, Zhang, Yaoyuan, Zhao, Yun, Otroshchenko, Tatiana, Lund, Henrik, Pohl, Marga-Martina, Rodemerck, Uwe, Linke, David, Jiao, Haijun, Jiang, Guiyuan, Kondratenko, Evgenii V.

Due to the complexity of heterogeneous catalysts, identification of active sites and the ways for their experimental design are not inherently straightforward but important for tailored catalyst preparation. The present study reveals the active sites for efficient C–H bond activation in C1–C4 alkanes over ZrO2 free of any metals or metal oxides usually catalysing this reaction. Quantum chemical calculations suggest that two Zr cations located at an oxygen vacancy are responsible for the homolytic C–H bond dissociation. This pathway differs from that reported for other metal oxides used for alkane activation, where metal cation and neighbouring lattice oxygen form the active site. The concentration of anion vacancies in ZrO2 can be controlled through adjusting the crystallite size. Accordingly designed ZrO2 shows industrially relevant activity and durability in non-oxidative propane dehydrogenation and performs superior to state-of-the-art catalysts possessing Pt, CrOx, GaOx or VOx species.

2023, Sabaghi, Davood, Wang, Zhiyong, Bhauriyal, Preeti, Lu, Qiongqiong, Morag, Ahiud, Mikhailovia, Daria, Hashemi, Payam, Li, Dongqi, Neumann, Christof, Liao, Zhongquan, Dominic, Anna Maria, Nia, Ali Shaygan, Dong, Renhao, Zschech, Ehrenfried, Turchanin, Andrey, Heine, Thomas, Yu, Minghao, Feng, Xinliang

The anion-intercalation chemistries of graphite have the potential to construct batteries with promising energy and power breakthroughs. Here, we report the use of an ultrathin, positively charged two-dimensional poly(pyridinium salt) membrane (C2DP) as the graphite electrode skin to overcome the critical durability problem. Large-area C2DP enables the conformal coating on the graphite electrode, remarkably alleviating the electrolyte. Meanwhile, the dense face-on oriented single crystals with ultrathin thickness and cationic backbones allow C2DP with high anion-transport capability and selectivity. Such desirable anion-transport properties of C2DP prevent the cation/solvent co-intercalation into the graphite electrode and suppress the consequent structure collapse. An impressive PF6−-intercalation durability is demonstrated for the C2DP-covered graphite electrode, with capacity retention of 92.8% after 1000 cycles at 1 C and Coulombic efficiencies of > 99%. The feasibility of constructing artificial ion-regulating electrode skins with precisely customized two-dimensional polymers offers viable means to promote problematic battery chemistries.

2017, Galbraith, M.C.E., Scheit, S., Golubev, N.V., Reitsma, G., Zhavoronkov, N., Despré, V., Lépine, F., Kuleff, A.I., Vrakking, M.J.J., Kornilov, O., Köppel, H., Mikosch, J.

Observing the crucial first few femtoseconds of photochemical reactions requires tools typically not available in the femtochemistry toolkit. Such dynamics are now within reach with the instruments provided by attosecond science. Here, we apply experimental and theoretical methods to assess the ultrafast nonadiabatic vibronic processes in a prototypical complex system - the excited benzene cation. We use few-femtosecond duration extreme ultraviolet and visible/near-infrared laser pulses to prepare and probe excited cationic states and observe two relaxation timescales of 11 ± 3 fs and 110 ± 20 fs. These are interpreted in terms of population transfer via two sequential conical intersections. The experimental results are quantitatively compared with state-of-the-art multi-configuration time-dependent Hartree calculations showing convincing agreement in the timescales. By characterising one of the fastest internal conversion processes studied to date, we enter an extreme regime of ultrafast molecular dynamics, paving the way to tracking and controlling purely electronic dynamics in complex molecules.