  Novel photoelectrocatalysts that use sunlight to power the CO$_2$ reduction
reaction will be crucial for carbon-neutral power and energy-efficient
industrial processes. Scalable photoelectrocatalysts must satisfy a stringent
set of criteria, such as stability under operating conditions, product
selectivity, and efficient light absorption. Two-dimensional materials can
offer high specific surface area, tunability, and potential for
heterostructuring, providing a fresh landscape of candidate catalysts. From a
set of promising bulk CO$_2$ reduction photoelectrocatalysts, we screen for
candidate mono-layers of these materials, then study their catalytic
feasibility and suitability. For stable monolayer candidates, we verify the
presence of visible-light band gaps, check that band edges can support CO$_2$
reduction, determine exciton binding energies, and compute surface reactivity.
We find for SiAs, ZnTe, and ZnSe monolayers, visible light absorption is
possible, and reaction selectivity biases towards CO production. We thus
identify SiAs, ZnTe, and ZnSe monolayers as targets for further investigation,
expanding the chemical space for CO$_2$ photoreduction.
