  Recent synthesis of monolayer fullerene networks [$Nature$ 606, 507 (2022)]
provides new opportunities for photovoltaics and photocatalysis because of
their versatile crystal structures for further tailoring of electronic, optical
and chemical function. To shed light on the structural aspects of
photocatalytic water splitting performance of fullerene nanomaterials, we
compare the photocatalytic properties of individual polymeric fullerene chains
and monolayer fullerene networks from first principles calculations. It is
found that the photocatalytic efficiency can be further optimised by reducing
dimensionality from 2D to 1D. The conduction band edge of the polymeric
C$_{60}$ chain provides a much higher external potential for the hydrogen
reduction reaction than its monolayer counterparts over a wider range of pH
values, and the surface active sites in the 1D chain are two times more than
those in the 2D networks from a thermodynamic perspective. These observations
render the 1D fullerene polymer a more promising candidate as a photocatalyst
for the hydrogen evolution reaction than monolayer fullerene networks.
