  At photoelectrosynthetic interfaces, an electrochemical reaction is driven by
excited charge-carriers from a semiconducting photoabsorber. Structure and
composition of this interface determine both the electronic and electrochemical
performance of devices, yet this structure is often highly dynamic both in the
time-domain and upon applied potentials. We discuss the arising challenges from
this dynamical nature and review recent approaches to gain an atomistic
understanding of the involved processes, which increasingly involves a
combination of experimental and computational methods. Bearing a similarity to
solid-electrolyte interphase formation in batteries, their apprehension could
help to develop functional passivation layers for high-performance
photoelectrosynthetic devices.
