Exploitation of a spontaneous spatial charge separation effect in plasmonic polyhedral α-Fe₂O₃ nanocrystal photoelectrodes for hydrogen production

High specific surface area bipyramidal and pseudocubic polyhedral α-Fe₂O₃ nanocrystals were fabricated for hydrogen reduction in a water-splitting process. Two different facets of polyhedral α-Fe₂O₃ nanocrystals were synthesized via a versatile hydrothermal route. Typically, photocatalytic activity of hematite is limited by its relatively poor absorptivity, very short excited-state lifetime, and short hole diffusion length. To address these issues, a pseudocubic polyhedral α-Fe₂O₃ photoelectrode was fabricated that achieved a spontaneous charge spatial separation during the water-splitting process. Additionally, Sn from the FTO substrate was diffused and doped into polyhedral α-Fe₂O₃ during the sintering process to serve as an electron donor and increase the carrier density. To further exploit the surface plasmon resonance (SPR) properties and enhance the water-splitting efficiency of polyhedral α-Fe₂O₃ photoelectrodes, Au nanoparticles were decorated on the surface of Fe₂O₃. This increased incident light absorption and suppressed charge recombination by the strong field generated from collective oscillations of surface electrons in the Au nanoparticles. Subsequently, this Au/pseudocubic Fe₂O₃ photoelectrode demonstrated a 9.05 μmol/min hydrogen production rate.