Skeletal Cu₇S₄ Nanocages Wrapped by Few-Layered Black Phosphorus Nanosheets as an Efficient H₂ Production Photocatalyst

Superstructures with hollow cage-like hierarchical ordering play a predominant role in various applications owing to their unique properties, such as low density, an interior void, a high surface-to-volume ratio, and excellent permeability for charge and mass transport. Low-cost hollow cage-like copper sulfide superstructures are competitive candidates for optical and electrochemical applications because of their outstanding conductivity and extensive number of active sites. Thus, we synthesized crystallinity-controlled nanotwinned polyhedral-skeletal-type copper sulfide cages (Cu₇S₄). Further, these cages were wrapped by few-layered black phosphorus (BP) nanosheets using simple strategies and tested for photocatalytic hydrogen production. The BP/Cu₇S₄ hybrid material exhibited improved hydrogen production, i. e., 0.475 μmol h⁻¹, which was 14-fold greater than that achieved using pristine Cu₇S₄ cages under optimal conditions. The enhanced activity was attributed to effective charge-carrier separation and transportation owing to the advanced unique properties of skeletal-type Cu₇S₄ cages and few-layered BP nanosheets. To the best of our knowledge, this is the first report of a BP-nanosheet-wrapped Cu₇S₄ system for photocatalytic hydrogen production. This system combining skeletal hollow cages with BP nanosheets is a new, fascinating, and inspiring approach for photocatalytic water-splitting applications.