Unveiling Failure of Gold Nanoclusters and Stabilization Strategies in the Gold Nanocluster‐Catalyzed TiO 2 ‐Based Photoelectrode Design for Water Splitting Reaction

Gold nanoclusters (AuNCs) have attracted attention as candidate photosensitizers because of their distinctive energy‐level characteristics. Coupling AuNCs with wide‐bandgap semiconductors such as solar irradiation by the semiconductor. Nevertheless, AuNCs readily aggregate and may deactivate under prolonged illumination, which limits sustained photoresponse. In this work, the cationic polymer polyethyleneimine (PEI) was introduced as a surface modifier to enhance the stability of AuNCs anchored on TiO 2 nanotube arrays. Owing to electrostatic interactions, the negatively charged AuNCs bind more firmly to the PEI‐treated TiO 2 surface, resulting in improved durability. In addition, the electronic structure of PEI promotes the separation of photogenerated charge carriers, leading to a marked increase in photocurrent density. Molecular dynamics simulations further indicate that PEI functionalization of TiO 2 substrates substantially improves the thermal stability of Au–GSH nanoparticles by facilitating heat dissipation and inhibiting sintering at elevated temperatures. Finally, AuNCs and PEI were coated with a Nafion layer to mitigate attack from aqueous electrolytes while preserving efficient electron transport pathways.