Synthesis Control of Charge Separation at Anatase TiO₂ Thin Films Studied by Transient Surface Photovoltage Spectroscopy

Abstract

For the efficient photocatalytic oxidation of organic pollutants at surfaces of semiconductors, photogenerated holes shall be separated toward the surface and transferred to reactive surface sites, whereas the transfer of photogenerated electrons toward the surface shall be minimized. In this Research Article, the identification of suitable synthesis control of charge separation combined with an in-depth understanding of charge kinetics and trapping passivation mechanisms at the related surfaces can provide tremendous opportunities for boosting the photocatalytic performance. In this work, a comprehensive transient surface photovoltage spectroscopy study of charge separation at anatase TiO 2 thin films, synthesized by ultrasonic spray pyrolysis from titanium(IV) isopropoxide (TTIP)−acetylacetone (AcacH) based precursor is reported. By varying the amount of AcacH in the precursor solution, an experimental approach of synthesis control of the charge transfer toward TiO 2 surface is provided for the first time. An increased amount of AcacH in the precursor promotes transition from preferential fast electron to preferential fast hole transfer toward anatase surface, correlating with a strong increase of the photocatalytic decomposition rate of organic pollutants. Suitable mechanisms of AcacH-induced passivation of electron traps at TiO 2 surfaces are analyzed, providing a new degree of freedom for tailoring the properties of photocatalytic systems.

Concentrated solar CO2 reduction in H2O vapour with >1% energy conversion efficiency

“…4b ) because Ni and V o can accept photo-generated charge carriers from CeO 2 through interface charge transfer, improving the separation efficiency. Transient surface photo-voltage (TPV) spectroscopy measures the SPV signal as a function of the photon energy and relaxation time 30 . For the CO 2 reduction reaction, the photo-generated electrons must migrate towards the outer surface, generating SPV signal peaks in the downward direction.…”

Transparent TiO2 thin films with high photocatalytic activity for indoor air purification

“…The SPV signal changed from negative to positive with an increase in AcacH molar ratio, which allows us to control the charge transfer toward the TiO 2 surface during the synthesis of the lm. 36 The recombination of the electron-hole pairs is reduced and more reactive oxygen species (ROS) are produced, which enhance the photocatalytic activity. 27,28,35,36 The generation of ROS plays an essential role in photocatalytic reactions since ROS can degrade a wide range of organic pollutants.…”

“…36 The recombination of the electron-hole pairs is reduced and more reactive oxygen species (ROS) are produced, which enhance the photocatalytic activity. 27,28,35,36 The generation of ROS plays an essential role in photocatalytic reactions since ROS can degrade a wide range of organic pollutants. [37][38][39] The lm obtained in the current study shows superhydrophilic properties aer 15 min of UV-A irradiation; 27 thus a short ca.…”

One-pot Synthesis of a Visible-light Responsive Carbon Nitride/TiO2 Heterointerface Material for Photoelectrocatalytic Applications

“…[2,3] TiO2 presents a few drawbacks, namely fast recombination kinetics and a wide band gap that limits solar light absorption. [4] Strategies like doping, [5] single-atom anchoring, [6] nanostructuring, [7] photonic engineering, [8] adding surface plasmons, [9] surface functionalization or passivation, [10] facet modulation, [11] and mesoporous structures, [12] co-catalysts, [13] and heterojunctions [14] have been applied to address these drawbacks. [4] Heterojunction is an interface between two distinct SCs, which are versatile hybrid materials in photoand electro-catalysis.…”