  Recent experiments claimed that the enhancement of catalytic reaction rates
occurs via the reduction of activation barriers driven by non-equilibrium
(``hot'') electrons in plasmonic metal nanoparticles. These experiments place
plasmonic photo-catalysis as a promising path for enhancing the efficiency of
various chemical reactions. Here, we argue that what appears to be
photo-catalysis is in fact thermo-catalysis, driven by the well-known
plasmon-enhanced ability of illuminated metallic nanoparticles to serve as heat
sources. Specifically, we point to some of the most important papers in the
field, and show that a simple theory of illumination-induced heating can
explain the extracted experimental data to remarkable agreement, with minimal
to no fit parameters. We further show that any small temperature difference
between the photocatalysis experiment and a control experiment performed under
uniform external heating is effectively amplified by the exponential
sensitivity of the reaction, and very likely to be interpreted incorrectly as
``hot'' electron effects.
