  Although significant insights have been obtained into chemical and physical
properties that govern to the performance of catalysts in traditional thermal
processes, the work on electro-, photo-, or plasma-catalytic approaches has
been comparatively limited. The effect of (local) surface charges in these
processes, while most likely a crucial factor of their activity, has not been
well-characterized and is difficult to study in a consistent, isolated manner.
Even theoretical calculations, which have traditionally allowed for the
untangling of the atomic-level mechanisms underpinning the catalytic process,
cannot be readily applied to this class of problems because of their inability
to properly treat systems carrying a net charge. Here, we report on a new,
generic, and practical approach to deal with charged semiperiodic systems in
density functional calculations, which can be readily applied to problems
across surface science. Using this method, we investigate the effect of a
negative catalyst surface charge on CO$_2$ activation by supported
M/Al$_2$O$_3$ (M = Ti, Ni, Cu) single atom catalysts. The presence of an excess
electron dramatically improves the reductive power of the catalyst, strongly
promoting the splitting of CO$_2$ to CO and oxygen. The relative activity of
the investigated transition metals is also changed upon charging, suggesting
that controlled surface charging is a powerful additional parameter to tune
catalyst activity and selectivity.
