Oriented Crystal Polarization Tuning Bulk Charge and Single‐Site Chemical State for Exceptional Hydrogen Photo‐Production

Rapid bulk charge recombination and mediocre surface catalytic sites harshly restrict the photocatalytic activities. Herein, the aforementioned concerns are well addressed by coupling macroscopic spontaneous polarization and atomic-site engineering of CdS single-crystal nanorods for superb H₂ photo-production. The oriented growth of CdS nanorods along the polar axis, vectorially superimposing substantial polar units with orderly arrangement, renders a strong polarization electric field (20.1 times enhancement), which boosts bulk charge separation with an efficiency up to 72.4% (80.4-fold). Remarkably, polarization electric field alters the chemical state of Pt single sites by orderly reducing the binding energy of Pt atom with stepwise polarization enhancement of CdS substrate, which increases the onsite electron density of Pt from 10.232 to 10.261e^- and *H key intermediates, providing preponderant Volmer-Tafel/Volmer-Heyrovsky reaction pathways with significantly decreased energy barriers for H₂ production. Thus, highly polarized CdS nanorods with atomically dispersed Pt sites perform an outstanding H₂ space-time yield of 118.5 mmol g^-1 h^-1 and apparent quantum efficiency of 57.7% at λ = 420 nm, and a record-high H₂ turnover frequency of 57798.4 h^-1, being one of the best catalysts for photocatalytic H₂ evolution. This work highlights the function of polarization in manipulating charge separation and catalytic reaction.