  Photoexcited metals can produce highly-energetic hot carriers whose
controlled generation and extraction is a promising avenue for technological
applications. While hot carrier dynamics in Au-group metals have been widely
investigated, a microscopic description of the dynamics of photoexcited
carriers in the mid-infrared and near-infrared Pt-group metals range is still
scarce. Since these materials are widely used in catalysis and, more recently,
in plasmonic catalysis, their microscopic carrier dynamics characterization is
crucial. We employ \emph{ab initio} many-body perturbation theory to
investigate the hot carrier generation, relaxation times, and mean free path in
bulk Pd and Pt. We show that the direct optical transitions of photoexcited
carriers in this metals are mainly generated in the near-infrared range. We
also find that the electron-phonon mass enhancement parameter for Pt is 16 $\%$
higher than Pd, a result that help explains several experimental results
showing diverse trends. Moreover, we predict that Pd (Pt) hot electrons possess
total relaxation times of up to 35 fs (24 fs), taking place at approximately
0.5 eV (1.0 eV) above the Fermi energy. Finally, an efficient hot electron
generation and extraction can be achieved in nanofilms of Pd (110) and Pd (100)
when subject to excitation energies ranging from 0.4 to 1.6 eV.
