Extended visible to near-infrared harvesting of earth-abundant FeS2–TiO2 heterostructures for highly active photocatalytic hydrogen evolution

Abstract

Photocatalytic water splitting is a key technology for long-term hydrogen evolution with low environmental impact. In this work, an environment-friendly photocatalyst consisting of FeS₂–TiO₂ heterostructured nanocrystals has been successfully prepared by wet chemical synthesis for enhancing the photocatalytic hydrogen production rate over a wide range of absorption wavelengths. Its absorption range has been extended from the ultraviolet–visible to near-infrared (NIR) spectrum. The results of ultrafast optical spectroscopy suggest that charge transfer occurs between the FeS₂ and TiO₂ interface under NIR pulsed laser irradiation (800 nm). The highest photocatalytic hydrogen production rate of the FeS₂–TiO₂ heterostructure has been obtained in comparison with FeS₂ nanocrystals (NCs) and TiO₂ nanoparticles (NPs) under irradiation by a mercury arc lamp or a xenon lamp. In the FeS₂–TiO₂ heterostructure, the FeS₂ NCs as a light harvester can efficiently absorb visible and NIR light to generate much more photoelectrons than TiO₂ NPs only for hydrogen production. For long-term photocatalytic hydrogen production, the FeS₂–TiO₂ heterostructures also reveal an outstanding durability over 40 h. Overall, the FeS₂–TiO₂ heterostructure shows potential to be a TiO₂-based photocatalyst for clean hydrogen production in practical applications.