Increase of the Ni/W ratio in heteropolyanions based NiW hydrocracking catalysts with improved catalytic performances

In the present work, we investigated the influence of the increase ofNi/W ratio by the addition of nickel nitrate on heteropolycompound (HPC) based catalysts. Synthesized catalysts were characterized by Raman, XPS and HRTEM techniques and were examined in the model reaction of toluene hydrogenation. The Ni2SiW12O40based catalyst with a ratio of 0.36 obtained by addition of nickel nitrate was found to have the best catalytic activity compared to the most efficient of the HPC based catalysts with a stoichiometric Ni/W ratio of 0.36. Raman spectroscopy showed that the SiW12O404-HPA was decomposed during the drying step in SiW11O398-species

Electron Paramagnetic Resonance Tracing of Electronic Transfers in Push-Pull Copolymers/PCBM or Nanocrystal Composites

International audienceTransfers of photoexcited electrons between poly(thieno[3,4-c]pyrrole-4,6-dione)-based copolymers (push-pull type) and fullerene or nanocrystals were studied by light-induced electron paramagnetic resonance (EPR). EPR tracing methodology has been used: EPR signatures of the various species taking part in the electron-transfer processes were determined and used to monitor potential charge transfers in the studied composites. The EPR tracing method combined with DFT calculations revealed that excited electrons are not only promoted from the HOMO of the polymer but also from its HOMO - 1 and even HOMO - 2, which are either exclusively centered on the push moiety or delocalized over both the push and pull units