Bio-inspired multilayered graphene-directed assembly of monolithic photo-membrane for full-visible light response and efficient charge separation

Abstract

Highly efficient and easily recyclable monolithic photocatalysts with elaborate hierarchical heterostructure and functional components are desirable to tap solar energy and produce green hydrogen fuels for the sustainable future. Inspired by the natural leaves, here we have rationally designed and fabricated an efficient artificial leaf photocatalyst, i.e., the first monolithic photomembrane of CdS/ZnO nanocage arrays grown into the interspaces of multilayered reduced graphene oxide (rGO) nanosheets (denoted as CdS/ZnO/rGO). The CdS/ZnO/rGO have elaborate hierarchical porous heterostructure and multifunctional components, such as multilayer rGO nanosheets for visible light absorption/harvesting, rapid charge transport and collection, hollowed CdS/ZnO nanocage arrays for light harvesting and charge utilization, and multiple heterojunction interfaces for efficient charge separation. It can been used not only as a monolithic photocatalyst, but also directly as a freestanding photoanode in the photoelectrochemical (PEC) cell system, exhibits an enhanced performance of photocatalytic (PC) or PEC hydrogen generation under different monochrome light irradiation in full-visible light region. Moreover, the CdS/ZnO/rGO photo-membrane can macroscopically realize the separation of photogenerated hole elimination and hydrogen generation by adjusting co-catalysts loading position. Impressively, it still delivered a PC H2 generation activity (0.79 μmol cm−2 h-1) and a photocurrent response of 250 μA cm-2 even under near-infrared light (λ = 700 nm) irradiation, a striking feature rarely achieved in prior arts.