Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

In photocatalysis, both the photogenerated charge separation and transport and the induced light utilization greatly influence performance. In this work, highly ordered CdS@ZnO core-shell inverse opal (CdS@ZnO-csIO) nanocomposites have been successfully designed as a model to couple the heterojunction system with the slow photon effect for photocatalytic H₂ production. Theoretical calculations and experimentation provide direct evidence for the slow photon effect in the CdS@ZnO-csIO nanocomposites. The type II heterojunction is responsible for promoting the migration and separation of photogenerated charges, and the slow photon effect is in charge of enhancing light harvesting in the CdS@ZnO-csIO nanocomposites. This synergy of two functions gives rise to a significantly enhanced photocatalytic H₂ production rate under simulated solar light for the CdS@ZnO-csIO nanocomposites. The highest H₂ production rate reaches 48.7 mmol g⁻¹ h⁻¹ under simulated solar light with the benchmark performance for all reported CdS@ZnO composites. Our work provides proof-of-principle that coupling the heterojunction system with the slow photon effect can greatly enhance the photocatalytic activity of composite photocatalysts.