Construction of THPP-sg-PSf/TiO2 membrane as photocatalyst for enhanced photoinduced hydrogen evolution

Abstract As an inorganic photocatalytic material, titanium dioxide (TiO2) is widely used in solar energy conversion. However, the application of TiO2 is limited due to its poor capability of collecting visible light, which results from its large band gap energy. In this work, a hydrogen generation system driven by UV-visible light was developed using monodispersed 5,10,15,20-meso-tetra(p-hydroxypheny) porphyrin (THPP) sensitized TiO2 as photocatalysts and chloromethylated polysulfone (CMPSf) membrane as the carrier and the linking agent. The CMPSf/TiO2 membrane (Mx, x is the mass fraction of the added TiO2) was prepared by nonsolvent induced phase separation (NIPS) method. The THPP was introduced onto the Mx membrane surface by in-situ surface grafting to obtain a novel THPP-sg-PSf/TiO2 (Py-Mx, y is the grafting time) photocatalysts membrane. The successful preparation of the Py-Mx was systematically characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The hydrogen production performance and the apparent quantum yield (AQY) of P12-M3 under 12 h UV-vis light irradiation are 9.74 mmol/m2 and 11.78% respectively, which are higher than that of recently reported typical dye-sensitized TiO2 photocatalysts. In addition, the excited state oxidation potential (Eox(dye*)), electron injection semiconductor Gibbs free energy (ΔGinject), transient fluorescence spectrum and the ground state (GS) frontier four-orbital energy levels of the catalysts were tested and calculated to illustrate the hydrogen evolution mechanism of the THPP-sg-PSf/TiO2 membrane. At the same time, the results of ESR reveal that the P12-M3 can produce a mass of electrons, which is the key for photocatalytic hydrogen production. This work provides a facile method to construct porphyrin sensitized TiO2 based photocatalysts membrane for solar energy conversion.