All‐Inorganic Perovskite@SiO ₂ Quantum Dots for Amplifying the Interfacial Electric Field on WO ₃ Toward Enhanced Photoelectrochemical Water Splitting

ABSTRACT All‐inorganic halide perovskite quantum dots (PQDs) encounter significant challenges related to degradation and self‐oxidation in aqueous electrolytes, which remain critical obstacles for their efficient utilization in photoelectrochemical (PEC) water oxidation. In this study, we demonstrate the hybridization of zero‐dimensional CsPbBr 3 PQDs with a SiO 2 shell (PQD@SiO 2 ) and the direct harnessing of PQD@SiO 2 on a two‐dimensional WO 3 nanoflake photoanode for boosting PEC water splitting. The ultra‐thin SiO 2 shell protects the PQDs from the aqueous environment and suppresses undesirable charge recombination. Incorporating PQD@SiO 2 enhances light harvesting and manipulates photogenerated charges, amplifying the interfacial electric field of the WO 3 photoanode to facilitate PEC water oxidation kinetics. Consequently, PQD@SiO 2 ‐incorporated WO 3 (PQD@SiO 2 /WO 3 ) exhibits 2.2‐fold higher PEC performance compared to pristine WO 3 at 1.23 V RHE , with long‐term durability over 12 h and a remarkable Faradaic efficiency of 85.5% for overall solar water splitting to produce H 2 at 1.23 V under 1 sun illumination. This novel strategy of a heterostructure consisting of PQDs passivated by an ultra‐thin SiO 2 shell on a WO 3 photoanode paves the way for improving PEC water splitting and efficient hydrogen production.