Effect of charge compensation on the photoelectrochemical properties of Ho-doped SrTiO3 films

Abstract

When Ho3+ ions are substituted at Sr2+ sites in SrTiO3 (STO), the excess positive charges are compensated via three complementary routes: (1) strontium vacancies, (2) titanium vacancies, and (3) conduction electrons. In this study, we show that the photoelectrochemical properties of Ho-doped STO films are dependent on the charge compensation mechanisms. The compensation mechanism via the titanium vacancies exhibits the highest photocurrent density, which is 1.7 times higher than that of the pure STO sample. Based on the measured dielectric properties and electrochemical impedance spectroscopy data, we propose that the enhanced dielectric constant of the films can enlarge the width of the space charge region at the film/liquid interface, which eventually leads to the increase of the photocurrent density. Further enhancement of photocurrent density is obtained in the samples decorated with appropriate amounts of Pt nanoparticles, showing the advantage of composites for achieving the efficient photoelectrochemical property.

Effect of crystallization on the band structure and photoelectric property of SrTiO3 sol–gel derived thin film

“…Similar to the previous report [12], the donor concentration of ST450, ST500, ST550, ST650, ST750 and ST800 in this work are estimated to be 1.4 Â 10 18 , 6.5 Â 10 17 , 6.6 Â 10 18 , 9.5 Â 10 18 , 6.4 Â 10 18 and 1.47 Â 10 19 cm À3 , respectively. It indicates that, in general, crystalline STO has a higher donor concentration than that of the amorphous STO thin films.…”

“…The optical absorption spectra of the films were measured by a UV/Vis/NIR spectrometer (U4100, HITACHI, Japan) in a wavelength range from 200 to 850 nm. The semiconductor type of the samples was determined by MotteSchottky plots from an electrochemical measurement using a conventional three-electrode cell (counter electrode: Pt, reference electrode: Ag/AgCl saturated calomel electrode (SCE), electrolyte: 1 mol/L Na 2 SO 4 solution) on an electrochemical analyzer (CHIe660C, China) [12]. The generation of photocurrent, in the presence of 1 mol/L Na 2 SO 4 solution as the supporting electrolyte, was recorded on an electrochemical workstation.…”

“…The region of potential barrier is known as the depletion layer, which will benefit the separation of photogenerated carriers and suppression of recombination rate of the photo-generated carriers. The photoelectric properties of the STO samples are strongly affected by the photo-generated charge separation efficiency [12]. It has been known that the width of the depletion layer is proportional to the Debye length and the Debye length largely depends on the grain size and the dielectric constant of the thin films [55].…”

Silver nanoparticles and defect-induced visible light photocatalytic and photoelectrochemical performance of Ag@m-TiO2 nanocomposite

“…7 presents a schematic representation of the photoinduced charge transfer, charge separation and degradation process of MO and MB in the presence of the Ag@m-TiO 2 and Ag@p-TiO 2 nanocomposites under visible light irradiation. Generally, a Schottky barrier is formed when materials with different work functions are combined, and the excited electrons are transferred from the materials with the lower work function to the materials with the higher work function until the two levels reach equilibrium to form a new Fermi energy level [35,36]. The equilibrated Fermi level electrons under visible light irradiation are injected rapidly into the conduction band of the metal oxide via a SPR phenomenon [35,36].…”

TiO2 Nanotubes with Different Ag Loading to Enhance Visible-Light Photocatalytic Activity

“…In addition, EIS spectra are used to compare the electronic transportation properties of the TNTs electrode and the Ag-TNTs samples electrode ( Figure 5), which is an effective tool for probing the photogenerated charge separation and transport properties [24][25][26]. The equivalent circuit contains 1 , PE , and 2 , where 1 is the bulk resistance of the electrolyte and electrodes and PE and 2 are the capacitance and the resistance formed at the interfaces of the electrodes, respectively.…”