3 of 25) 1601625 wileyonlinelibrary.com Adv. Energy Mater. 2017, 7, 1601625 www.advenergymat.de www.advancedsciencenews.com Figure 1. Comparison of the a) inorganic and b) organic carbon sources on the performance of carbon coated Li 4 Ti 5 O 12 .

A low-pressure premixed toluene/O 2 /Ar flame with the equivalence ratio of 1.90 was investigated using tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry. Combustion intermediates up to C 19 H 12 were identified by the measurements of the photoionization mass spectrum and photoionization efficiency spectrum. Mole fraction profiles of flame species were evaluated from the scan of burner position at photon energies near ionization thresholds. Furthermore, flame temperature was recorded by a Pt/Pt-13%Rh thermocouple. The comprehensive experimental data concerning the flame structure facilitate the discussion about the flame chemistry of toluene and other monocyclic aromatic fuels. Benzyl and benzene were found to be major primary intermediates of toluene degradation; and benzene is suggested to originate mainly from fuel degradation instead of radical recombination channels in fuel-rich monocyclic aromatic hydrocarbon flames. On the basis of the intermediate identification, comparison is made among the current mechanisms relevant to the formation of polycyclic aromatic hydrocarbons (PAHs). It is concluded that the molecular growth process in this flame is consistent with the synergy of the hydrogen-abstraction-carbon-addition (HACA) mechanism and the resonantly stabilized radical addition mechanism. In particular, the HACA mechanism can connect a great deal of aromatic intermediates observed in the present work and consequently explain the regular ring enlargement by consecutive addition of 2 or 4 carbon atoms, while the resonantly stabilized radical addition mechanism may have marked and sometimes predominant influences on the formation of many typical PAHs.

The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/ argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt-6%Rh/Pt-30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well.

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Metal anodes based on a plating/stripping electrochemistry such as metallic Li, Na, K, Zn, Mg, Ca, Al, and Fe have attracted widespread attention over the past several years because of their high theoretical specific capacity, low electrochemical potential, and superior electronic conductivity. Metal anodes can be paired with cathodes to construct high-energy-density rechargeable metal batteries. However, inherent issues including large volume changes, uncontrollable growth of dangerous dendrites, and an unstable solid electrolyte interphase (SEI) hinder their further development. MXene as an emerging 2D material has shown great potential to address the inherent issues of metal anodes due to its 2D structure, abundant surface functional groups, and the ability to construct macroscopic architectures. To date, under the assistance of MXene, various strategies have been proposed to achieve stable and dendrite-free metal anodes, such as MXene-based host design, designing metalphilic MXene-based substrates, modifying the metal surface with MXene, constructing MXene arrays, and decorating separators or electrolytes with MXene. Herein the applications and advances of MXene in stable and dendrite-free metal anodes are carefully summarized and analyzed. Some perspectives and outlooks for future research are also proposed.

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