Pyrite FeS2 Sensitized TiO2 Nanotube Photoanode for Boosting Near-Infrared Light Photoelectrochemical Water Splitting

Effective utilization of ultraviolet and visible light for hydrogen evolution in a photoelectrochemical (PEC) water splitting approach has been widely investigated, whereas infrared light, another major fraction of solar radiation (similar to 50%), is rarely reported for implementing PEC water splitting application. In this paper, we first demonstrate the coupling of air and solution stable pyrite iron disulfide (FeS2) with hierarchical top-porous-bottom-tubular TiO2 nanotubes (TiO2 NTs) to realize high PEC performance not only in the ultraviolet and visible light regions but also in the infrared light region with photocurrent enhancement by more than 3 orders of magnitude compared to that of the pristine TiO2 NTs under illumination of near infrared light. The significant enhancement of PEC performance can be ascribed to the rational coupling of FeS2 with a small band gap and TiO2 NTs with unique morphology and proper electronic features. We postulate the proposed novel FeS2/TiO2 NTs photoelectrode has the potential to address the low efficiency of PEC water spitting in the infrared light region, and thus can make a significant contribution in the field of energy conversion.