Polarons are a type of localized excess charge in materials
and
often form in transition metal oxides. The large effective mass and
confined nature of polarons make them of fundamental interest for
photochemical and electrochemical reactions. The most studied polaronic
system is rutile TiO2where electron addition results in
small polaron formation through the reduction of Ti(IV) d0to Ti(III) d1centers. Using this model system, we perform
a systematic analysis of the potential energy surface based on semiclassical
Marcus theory parametrized from the first-principles potential energy
landscape. We show that F-doped TiO2only binds polaron
weakly with effective dielectric screening after the second nearest
neighbor. To tailor the polaron transport, we compare TiO2to two metal–organic frameworks (MOFs): MIL-125 and ACM-1.
The choice of MOF ligands and connectivity of the TiO6octahedra
largely vary the shape of the diabatic potential energy surface and
the polaron mobility. Our models are applicable to other polaronic
materials.