Porous Hybrid Materials Based on Mesotetrakis(Hydroxyphenyl) Porphyrins and TiO₂ for Efficient Visible-Light-Driven Hydrogen Production

Abstract

A series of highly robust nano-micro hybrid materials based on meso-tetra(4-hydroxyphenyl) porphyrins (M = H, Pd, Zn) and titanium dioxide (denoted as THPP-TiO2, THPP-Pd-TiO2, and THPP-Zn-TiO2) have been prepared by a facile sol-gel method for the first time. When Pt nanoparticles are incorporated in these hybrids, Pt/THPP-Pd-TiO2 achieves good H2 production activity (2025.4 μmol g−1 h−1 and 12.03 μmol m−2 h−1), higher than that of Pt/THPP-Zn-TiO2 (1239.8 μmol g−1 h−1 and 7.46 μmol m−2 h−1) and Pt/THPP-TiO2 (576.8 μmol g−1 h−1 and 4.02 μmol m−2 h−1), owing to the different central metal ions in porphyrins. The best activity of Pt/THPP-Pd-TiO2 would be attributed to the two-center catalysis from coordination Pd metal ions and Pt nanoparticles, while the higher activity of Pt/THPP-Zn-TiO2 than Pt/THPP-TiO2 could be ascribed to the more effective light harvesting and electron transfer between THPP-Zn and TiO2. In addition, the hybridized Pt/THPP-Pd-TiO2 catalyst exhibits unattenuated hydrogen production stability even after recycling the experiment 10 times (cumulative turnover number of 5111 after 50 h), far superior to that of the surface-sensitized Pt/THPP-Pd/TiO2 catalyst with analogous components, due to the more stable Ti-O bonds between four phenols in porphyrins and TiO2 for the hybrid system. The present study provides a promising approach for constructing stable organic–inorganic hybrid systems with unique hierarchical structures for efficient light absorption and electron transfer.

Keywords

• porphyrin photosensitizer
• titanium dioxide
• organic–inorganic hybrid material
• photocatalytic H₂ evolution
• durability