Exploring Ultrafast Carrier Dynamics in Photoelectrochemical Water Splitting Using Transient Absorption Spectroscopy

Abstract Hydrogen fuel produced from water splitting using sunlight remains one of the cleanest and most sustainable energy sources. However, photoelectrochemical hydrogen production faces several challenges, including poor sunlight absorption, deficient charge carrier lifetime and transfer rates, and very sluggish kinetics of the water oxidation half‐reaction. To address these challenges, researchers have concentrated on enhancing the efficiency of photoelectrochemical water splitting. A critical factor in this enhancement is a deeper understanding of the fundamental processes involved in photoabsorption and the subsequent oxidation evolution reaction. The advent of ultrafast lasers has enabled the detailed tracking of charge carriers within materials after sunlight absorption, including their separation and migration to the surface for water oxidation. Ultrafast transient absorption spectroscopy is a powerful technique that allows real‐time observation of the behavior of excited states and charge carriers on femtosecond to nanosecond timescales. Recent studies utilizing ultrafast transient absorption spectroscopy are explored to investigate the dynamics of charge carriers in photoelectrochemical water splitting, providing insights into the mechanisms that lead to the design of enhanced photoanodes with improved efficiency.