Wafer-scale two-dimensional Au-TiO₂ bilayer films for photocatalytic degradation of Palmitic acid under UV and visible light illumination

Highlights: • Successful wafer-scale atomic layer deposition of 2D Au-TiO₂ bilayer photocatalyst films. • The efficient degradation of fatty acid by tailoring 2D TiO₂ films under UV and visible light illumination. • Improved visible light photocatalytic activity and photocurrent density of 2D Au-TiO₂ bilayer films. • Comparable photocatalytic performance of ultra-thin 2D TiO₂ and thick TiO₂ films under UV light illumination. - Abstract: Bilayer Au-TiO₂ configuration with two-dimensional (2D) TiO₂ films enabled sensible improvement in photocatalytic degradation of Palmitic Acid (PA) and also the enhancement of current density under visible light illumination. The improved visible light photocatalytic and photocurrent properties were attained when 35 nm thick 2D TiO₂ film was developed by atomic layer deposition (ALD) on Si/SiO₂-Au substrate. The Au-TiO₂ bilayer demonstrated the improved photocatalytic and photovoltaic performances compared with those TiO₂ films developed on Si/SiO₂ bare substrate. These improvements can be attributed to the plasmonic effects of Au film acting as antenna for visible light and also serving as hole acceptor during photocatalysis process. The proposed mechanisms for enhanced visible light performance of bilayer films are hot electron injection and the formation of hot spots at Au-TiO₂ interface which contributed to the electron injection to conduction band of TiO₂ or facilitated the separation of generated electron-hole pairs at Au-TiO₂ Schottky junction.