New insight into enhanced photocatalytic activity of morphology-dependent TCPP-AGG/RGO/Pt composites

The porphyrin aggregate is recognized as an attractive candidate for developing artificial light-harvesting systems. Using 5, 10, 15, 20-tetrakis-(4-carboxyphenyl) porphyrin (TCPP), the porphyrin aggregates with different morphologies (sphere, rod and flake) are controllably prepared by the surfactant-assisted self-assembly reaction, and then synthesize the ternary bionic-system (e.g. porphyrin composites). These composites are characterized by scanning-electron microscopy (SEM), atomic force microscope (AFM) and spectroscopic technology. The combinatorial technique consisted of ultraviolet-visible spectroscopy and scanning electrochemical microscopy (UV-vis/SECM) is used to record SECM approach curves of porphyrin photocatalysis under visible light illumination at the specific zones, where morphology-dependent porphyrin composite is recognized to be distributed evenly on ITO surface. Heterogeneous photoelectron transfer rates (keff) are given by simulating SECM approach curves. It is suggested that rod-like porphyrin aggregate composite has highest photocatalytic efficiency with the kinetics rate to be 8.624 × 10−2 cm s−1, the largest keff of which is obtained at the excitation wavelength of 469 nm. These findings are also proved by photocatalytic decomposition test of pollutants (methyl orange). It is indicated that one-dimensional nanostructure is advantageous for separation of electrons and holes and directional transmission of photoelectron.