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 ( k eff ) 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 k eff 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.