# Polarons in Heterogeneous Photo(electro)Catalysts

## TL;DR

This paper reviews how polarons, quasiparticles formed by electron-lattice interactions, impact the performance of photo(electro)catalysts and how they can be studied and engineered for better efficiency.

## Contribution

The paper provides a comprehensive and pedagogical overview of polaron phenomena in photo(electro)catalysts, linking their behavior to material performance.

## Key findings

- Polarons significantly influence photon absorption, charge transport, and surface reactivity in photo(electro)catalysts.
- Advanced experimental and numerical techniques now allow direct observation and analysis of polaronic states.
- Understanding polaron dynamics can guide the design of more efficient semiconductors for catalytic applications.

## Abstract

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.

Polarons are defined as quasiparticles consisting of electrons/holes covered by a cloud of virtual phonons, which are beneficial/detrimental to the electronic properties of materials. This minireview provides a conceptual overview of how small polaron formation influences the photon absorption, charge transport and separation, and surface reactivity in heterogeneous photo(electro)catalyts. The state‐of‐the‐art experimental and numerical techniques are also compiled.