Photoinduced Fabrication of Cu/TiO2 Core–Shell Heterostructures Derived from Cu-MOF for Solar Hydrogen Generation: The Size of the Cu Nanoparticle Matters

The inclusion of metal cocatalysts into the semiconductor photocatalysts is the most proficient way to separate the photoexcited charge carriers by providing additional reaction sites and is a typical way to enhance the efficiency of catalytic reactions. We report a new strategy for the synthesis of Cu/TiO2 core–shell photocatalyst supported on the amorphous TiO2 matrix based on the Cu-metal–organic framework (MOF) self-templating approach and employed in photocatalytic hydrogen production from water. The [Cu(tpa)(dmf)] MOF hollow nanocrystal encapsulated by amorphous-phase TiO2 is treated under controlled light with simple altered reaction conditions to produce the core–shell Cu/TiO2 hybrid nanoplatform. It resulted in spherical Cu nanoparticles (NPs) with the different sizes and (111) exposed facets. The localized field-mediated charge transfer properties and capacitive behavior at the anodic panel of the as-prepared photocatalysts suggest a low Schottky barrier at the homogeneous interfacial contacts between smaller Cu NP and the TiO2 and promotes the fast photoexcited charge separation during water splitting. Benefiting from the structural and compositional features, the 2 nm Cu/TiO2 photocatalyst manifests the hydrogen production rate of 334 μmol g–1 h–1, without employing the noble metal cocatalyst under 1.5 AM simulated light irradiation. The activity was further reinforced by the photolysis of alkaline water on the anode surface, which generated a steady-state geometric current density of 8 mA cm–2 at 1.23 V (vs reversible hydrogen electrode) with almost 50% incident photon-to-current conversion efficiency.