Polarons in Heterogeneous Photo(electro)Catalysts

Heterogeneous photo(electro)catalysis involves sequential steps of photon absorption, charge separation, polaron formation, trapping, bulk and surface recombination, charge extraction, and surface catalysis. Among these, the formation and dynamics of polarons, quasiparticles resulting from strong electron-lattice interactions, play a pivotal yet often underappreciated role. With ultrafast lifetimes ranging from femtoseconds to picoseconds, polarons are challenging to control, but they crucially influence photon absorption, charge carrier mobility, recombination rates, and catalytic reactivity. Recent advances in time-resolved spectroscopy, scanning probe microscopy, and theoretical modeling have enabled direct observation and mechanistic interpretation of polaronic states in various photoactive semiconductors. This minireview aims to provide a comprehensive and pedagogical overview of polaron phenomena in heterogeneous photo(electro)catalysts, with a focus on how they affect key material functionalities. Special emphasis is placed on correlating material performance with polaron behavior through state-of-the-art experimental characterization and modeling techniques. By highlighting mechanistic insights and unifying design principles, this minireview aims to guide the rational engineering of semiconductors with tailored polaronic properties for enhanced photo(electro)catalytic performance.