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 (∼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.