Performance of ferroelectric visible light type II Ag10Si4O13/TiO2 heterojunction photocatalyst

Abstract

Water remediation using semiconductor photocatalysts under visible light (VL) irradiance appears as a more sustainable technology option due to the greater penetration depth. Consequently, the overall band spectrum of VL has received significant attention to providing solutions to secure clean water resources over the past few decades. This research developed an innovative approach to enhancing the visible light susceptibility of semiconductor-based photocatalytic composites Ag10Si4O13/TiO2 (ASO/TO). The intrinsic properties of TO and electron donor ability of ASO lend synergistically to the generation of a narrow bandgap semiconductor. A feasible wet-chemistry method was found to engineer the electronic properties of ASO/TO under VL for rapid decolorization of methylene blue (MB). Inhibition experiments with several agents confirmed that the decolorization proceeds through the generation of hydroxyl radical species assisted by hole carrier generation at the ASO junction. The rate of MB decomposition followed a pseudo-first-order kinetic profile (98.2% within 35 mins under ambient conditions with 5 ppm of 2:1 ASO/TO and 20 ppm of MB). The XRD/XPS spectroscopic analysis confirms the electronic polarization of distorted SiO4 tetrahedral units coordinated to Ag-O, forming a double dumbbell double-helical structure. The staggered bandgap of these composite photocatalysts is associated with the Ag-Ag d10/sp hybridization and dispersive conduction band. At the same time, the 2p orbitals of TiO2 showed a less dispersive band due to the availability of d-orbitals. The generated Ag10Si4O13 (ASO) based ferroelectric materials allow amplifying its frequency due to internal polarization along the c-axis. The electrochemical evaluation also showed that the interface charge transfer resistance was lowered relative to TiO2, facilitating the efficacy of photocatalytic reactivity, where the generation of holes as charge carriers was the rate-limiting step. The novel nano-engineering strategy providing highly active photocatalysis can open new horizons for VL applications.