Integrated Au/TiO2 Nanostructured Photoanodes for Photoelectrochemical Organics Degradation

Abstract

In this work, hierarchical Au/TiO 2 nanostructures were studied as possible photoanodes for water splitting and bisphenol A (BPA) oxidation. TiO 2 samples were synthetized by Pulsed Laser Deposition (PLD), while Au nanoparticles (NPs) were differently dispersed (i.e., NPs at the bottom or at the top of the TiO 2 , as well as integrated TiO 2 /Au-NPs assemblies). Voltammetric scans and electrochemical impedance spectroscopy analysis were used to correlate the morphology of samples with their electrochemical properties; the working mechanism was investigated in the dark and in the presence of a light radiation, under neutral pH conditions towards the possible oxidation of both bisphenol A (BPA) and water molecules. Different behavior of the samples was observed, which may be attributed mainly to the distributions of Au NPs and to their dimension as well. In particular, the presence of NPs at the bottom seems to be the crucial point for the working mechanism of the structure, thanks to scattering effects that likely allow to better exploit the radiation.

Au-Ag/TiO2 Thin Films Preparation by Laser Ablation and Sputtering Plasmas for Its Potential Use as Photoanodes in Electrochemical Advanced Oxidation Processes (EAOP)

“…Nevertheless, for the PEC experiments, the Au-TiO 2 photoanode result in the highest kinetic reaction constant (0.02867 cm −1 ), but like the rest of the photoanode materials, further studies regarding the electric properties of the photoanodes are proposed, to fully understand how the incorporation of a single or combined metallic nanoparticle in the TiO 2 thin film could modify the donor concentration, due to the oxygen vacancies, or the interfacial electron transfer [51]. Nevertheless, for the PEC experiments, the Au-TiO2 photoanode result in the highest kinetic reaction constant (0.02867 cm −1 ), but like the rest of the photoanode materials, further studies regarding the electric properties of the photoanodes are proposed, to fully understand how the incorporation of a single or combined metallic nanoparticle in the TiO2 thin film could modify the donor concentration, due to the oxygen vacancies, or the interfacial electron transfer [51]. The degree of electrochemical enhancement (E) and the degree of process synergy (S) were calculated using Equations ( 1) and ( 2), as reported by [52,53].…”

Photocatalytic Fuel Cells for Simultaneous Wastewater Treatment and Power Generation: Mechanisms, Challenges, and Future Prospects

“…The Fermi level of photoexcited electrons in the CB should be higher than the energy level of the acceptor otherwise, the reducible chemical species is unable to receive electrons at the cathode. In addition, the level of the holes (h + ) in the VB of the semiconductor electrode should be at a lower position than that of the donor [83]. In the PFC couple designed by Chen et al, the WO 3 /W acts as a photoanode, and Cu 2 O/Cu acts as a photocathode where organic compounds can be decomposed (oxidized) by the holes of WO 3 /W photoanode only due to its higher oxidation power (approximately +3.1 V NHE ) [83].…”

“…In addition, the level of the holes (h + ) in the VB of the semiconductor electrode should be at a lower position than that of the donor [83]. In the PFC couple designed by Chen et al, the WO 3 /W acts as a photoanode, and Cu 2 O/Cu acts as a photocathode where organic compounds can be decomposed (oxidized) by the holes of WO 3 /W photoanode only due to its higher oxidation power (approximately +3.1 V NHE ) [83]. The WO 3 /W photoanode is an n-type semiconductor where the Fermi energy level is near the E VB , and the Cu 2 O/Cu acts as a p-type semiconductor where fermi energy lies near the E CB .…”

Self-Organized Plasmonic Nanowire Arrays Coated with Ultrathin TiO2 Films for Photoelectrochemical Energy Storage

“…So far, intense research efforts have been focused on overcoming these limitations to improve the performance of photocatalytic electrodes. Doping strategies have, e.g., been adopted to reduce the band gap of photocatalytic materials, while heterojunctions have been fabricated to increase the separation rate of photoexcited carriers. , A promising approach is based on the excitation of localized plasmon resonances in nanoparticles to promote photoconversion efficiency and to control the selectivity in photocatalysis. − Under this condition, the ultrafast temporal dynamics and decay of plasmonic “hot-electrons” have recently attracted considerable attention as an effective carrier injection channel in photocatalysis. − In parallel, the characteristic plasmonic near-field confinement has been shown to play a relevant role in these processes . Very recently, novel strategies and materials have also been investigated to exploit light-induced photothermal effects in catalysis without the need for extreme concentration to achieve high temperatures. , …”