Solar-light-sensitive applications of recycled iron oxyhydroxide as photoelectrolytic heterostructure by encapsulating in reduced graphene oxide and titanium oxide nanotube array (FeOxrGO/TiNTA)

Abstract

FeOxrGO/Ti photoanodes by decorating TiO2 nanotube array (TiNTA) with waste iron oxide and reduced graphene oxide (rGO) were synthesized via wet impregnation and calcination. Photoelectrocatalytic (PEC) degradation of azo dye pollutants, accompanied by hydrogen gas evolution, was demonstrated in a dual-chamber divided cell. Characterization showed that the iron oxide recovered from the wastewater treatment plant were crystalline clusters consisting of mineral goethite nanoparticles (αFeOOH NPs) with a visible-light responsive bandgap. Furthermore, the incorporation of rGO led to an enhancement in the electrochemical surface area (ECSA, cm2) of the anode due to its larger capacitive current compared to TiNTA. This improvement facilitated the transport of charge carriers (e- and h+) within a type-II heterostructure of αFeOOH and TiO2. The applied bias photon-to-current conversion efficiency and transient photocurrent density, depending on the composition of iron oxide in FeOxrGO/Ti, substantially increased. 2%wt of iron oxide in FeO2.0rGO/Ti has been optimized in terms of azo dye decolorization, TOC removal, and H2 generation rates (on Pt/G cathode) in 0.1 M Na2SO4 at a working potential of +1.0 V (vs. Ag/AgCl). This study explored the reusability and valorization of Fenton fluidized-bed waste iron oxide with TiO2 for PEC applications.