From Photon Absorption to Hydrogen Evolution: Addressing Energy Losses in Photocatalytic Systems

Abstract Hydrogen, as a clean and sustainable energy carrier holds immense promise in addressing the global energy crisis. Photocatalytic water splitting, a key method for hydrogen production, faces significant challenges due to various loss mechanisms that impede its efficiency. These losses are primarily caused by photogenerated charge recombination, underutilization of the available electromagnetic spectrum, and kinetic limitations in the reaction process, especially during oxygen evolution. Fast charge recombination and slow hole extraction significantly reduce the photocatalytic quantum yield, thus preventing photocatalysts from achieving their theoretical maximum efficiency. Strategies such as bandgap engineering, plasmonic metal nanoclusters, and the incorporation of upconverting materials have been explored to extend the absorption range and minimize energy losses. Moreover, advancements in enhancing charge carrier dynamics through morphological modifications and the use of selective cocatalysts have proven effective in improving photocatalytic performance. Despite the thermodynamic feasibility of photocatalytic water splitting, slow kinetics, particularly during water oxidation, remain a major challenge. This review consolidates and extensively examines the various loss mechanisms in photocatalysis, their potential solutions, and provides insightful perspectives for future advancements, ultimately aiming to unlock the full potential of photochemical water splitting in practical applications.