  We investigate the photocatalytic performance of nanocomposites prepared in a
one-step process by liquid-phase exfoliation of graphite in the presence of
TiO$_2$ nanoparticles (NPs) at atmospheric pressure and in water, without
heating or adding any surfactant, and starting from low-cost commercial
reagents. The nanocomposites show enhanced photocatalytic activity, degrading
up to 40$\%$ more pollutants with respect to the starting TiO$_2$-NPs. In order
to understand the photo-physical mechanisms underlying this enhancement, we
investigate the photo-generation of reactive species (trapped holes and
electrons) by ultrafast transient absorption spectroscopy. We observe an
electron transfer process from TiO$_2$ to the graphite flakes within the first
picoseconds of the relaxation dynamics, which causes the decrease of the charge
recombination rate, and increases the efficiency of the reactive species
photo-production.
