Photocatalytic Hydrogen Production by the Sensitization of Sn(IV)-Porphyrin Embedded in a Nafion Matrix Coated on TiO2

Efficient utilization of visible light for photocatalytic hydrogen production is one of the most important issues to address. This report describes a facile approach to immobilize visible-light sensitizers on TiO2 surfaces. To effectively utilize the sensitization of Sn(IV) porphyrin species for photocatalytic hydrogen production, perfluorosulfonate polymer (Nafion) matrix coated-TiO2 was fabricated. Nafion coated-TiO2 readily adsorbed trans-diaqua[meso-tetrakis(4-pyridinium)porphyrinato]tin(IV) cation [((TPyP)-P-H)Sn(OH2)(2)](6+) via an ion-exchange process. The uptake of [((TPyP)-P-H)Sn(OH2)(2)](6+) in an aqueous solution completed within 30 min, as determined by UV-vis spectroscopy. The existence of Sn(IV) porphyrin species embedded in the Nafion matrix coated on TiO2 was confirmed by zeta potential measurements, UV-vis absorption spectroscopy, TEM combined with energy dispersive X-ray spectroscopy, and thermogravimetric analysis. Sn(IV)-porphyrin cationic species embedded in the Nafion matrix were successfully used as visible-light sensitizer for photochemical hydrogen generation. This photocatalytic system performed 45% better than the uncoated TiO2 system. In addition, the performance at pH 7 was superior to that at pH 3 or 9. This work revealed that Nafion matrix coated-TiO2 can efficiently produce hydrogen with a consistent performance by utilizing a freshly supplied cationic Sn(IV)-porphyrin sensitizer in a neutral solution.

Automated summary

This report describes a facile approach to immobilize visible-light sensitizers on TiO2 surfaces for efficient photocatalytic hydrogen production. By coating TiO2 with perfluorosulfonate polymer (Nafion), the sensitization of Sn(IV) porphyrin species was effectively utilized to enhance the hydrogen generation. The Nafion coated-TiO2 readily adsorbed the porphyrin cation Sn(IV) species via an ion-exchange process, resulting in a significant improvement in photocatalytic performance.