Low‐Energy Facets on CdS Allomorph Junctions with Optimal Phase Ratio to Boost Charge Directional Transfer for Photocatalytic H2 Fuel Evolution

Low‐energy facets on CdS allomorph junctions with optimal phase ratio are designed to boost charge directional transfer for photocatalytic H₂ fuel evolution. Fermi energy level difference between low‐energy facets as driving force promotes electrons directional transfer to hexagonal CdS(102) facet and holes to cubic CdS(111) facet. The optimal allomorphs CdS presents superior photocatalytic H₂ evolution rate of 32.95 mmol g^?1 h^?1 with release in a large amount of visible H₂ bubbles, which is much higher than single‐phase CdS with high‐energy facets and even supports noble metal photocatalysts. This scientific perspective on low‐energy facets of allomorph junctions with optimal phase ratio breaks the long‐held view of pursuing high‐energy crystal surfaces, which will break the understanding on surface structure crystal facet engineering of photocatalytic materials.