Enhanced visible-light-induced photocatalytic activity of α-Fe2O3 adsorbing redox enzymes

• Hybrid photocatalyst composed of enzyme and hematite was prepared.
• The hybridization process occurred via physical adsorption.
• The hybrid showed a higher activity than bare hematite under visible light.
• We report a synergistic effect of enzyme and hematite during the reaction.

We report fabrication of hybrid photocatalyst composed of an n-type semiconductor (α-Fe2O3) and a redox enzyme (horseradish peroxidase; HRP), and its performance for oxidation of luminol in an aqueous solution. The hybrid photocatalyst is simply formed via physical adsorption of HRP to an α-Fe2O3 sintered body. Under visible light irradiation, the bare α-Fe2O3 with a narrow bandgap photocatalytically oxidizes luminol along with blue emission that can be used as an indicator of the photocatalytic performance. The blue emission is largely strengthened after the adsorption of HRP, demonstrating that the presence of enzyme improves apparent photocatalytic activity of α-Fe2O3. The favorable effect is derived from synergistic oxidation of luminol by the biocatalysts (HRP) as well as by the photocatalyst (α-Fe2O3). In this paper, influence of excitation wavelength, adsorption amount of HRP, and reaction temperature on the overall photocatalytic activity are elucidated, and then a reaction mechanism of the proposed novel hybrid photocatalyst is discussed in detail.