Abstract:
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The realization of artificial photosynthesis may depend on the
efficient integration of photoactive semiconductors and catalysts
to promote photoelectrochemical water splitting. Many
efforts are currently devoted to the processing of multicomponent
anodes and cathodes in the search for appropriate synergy
between light absorbers and active catalysts. No single material
appears to combine both features. Many experimental
parameters are key to achieve the needed synergy between
both systems, without clear protocols for success. Herein, we
show how computational chemistry can shed some light on
this cumbersome problem. DFT calculations are useful to predict
adequate energy-level alignment for thermodynamically
favored hole transfer. As proof of concept, we experimentally
confirmed the limited performance enhancement in hematite
photoanodes decorated with cobalt hexacyanoferrate as a
competent water-oxidation catalyst. Computational methods
describe the misalignment of their energy levels, which is the
origin of this mismatch. Photoelectrochemical studies indicate
that the catalyst exclusively shifts the hematite surface state to
lower potentials, which therefore reduces the onset for water
oxidation. Although kinetics will still depend on interface architecture,
our simple theoretical approach may identify and predict
plausible semiconductor/catalyst combinations, which will
speed up experimental work towards promising photoelectrocatalytic
systems. |