High Concentration Of Oxygen Vacancies Research Articles

Engineering Oxygen Vacancies in In2O3 with Enhanced Polysulfides Immobilization and Selective Catalytic Capability.

Lithium-sulfur (Li-S) battery is identified as an ideal candidate for next-generation energy storage systems in consideration of its high theoretical energy density and abundant sulfur resources. However, the shuttling behavior of soluble polysulfides (LiPSs) and their sluggish reaction kinetics severely limit the practical application of the current Li-S battery. In this work, a series of In2O3 nanocubes with different oxygen vacancy concentrations are designed and prepared via a facile self-template method. The introduced oxygen vacancy on In2O3 can effectively rearrange the charge distribution and enhance sulfiphilic property. Moreover, the In2O3 with high oxygen vacancy concentration (H-In2O3) can slightly slow down the solid-liquid conversion process and significantly accelerate the liquid-solid conversion process, thus reducing the accumulation of LiPSs in electrolyte and inhibiting the shuttle effect. Contributed by the unique selective catalytic capability, the prepared H-In2O3 exhibits excellent electrochemical performance when used as sulfur host. For instance, a high reversible capacity of 609 mAh g-1 is obtained with only 0.044% capacity decay per cycle over 1000 cycles at 1.0C. This work presents a typical example for designing advanced sulfur hosts, which is crucial for the commercialization of Li-S battery.

Synaptic properties of GaOx-based memristor with amorphous GaOx deposited by RF magnetic sputtering

GaOx devices have been extensively explored for applications such as power devices and solar blind detectors, based on their wide bandgap. In this study, we investigated the synaptic properties of the amorphous gallium oxide (a-GaOx)- based memristor with a W/WOx/a-GaOx/ITO structure, in which a-GaOx are deposited by RF magnetic sputtering at ambient temperature. The structure and components of a-GaOx are characterized by XRD, XPS, SEM, and EDS. The electrical test indicates that W/WOx/a-GaOx is ohmic due to the thin WOx layer with a high concentration of oxygen vacancies. Consequently, the synaptic characteristics of the W/WOx/a-GaOx/ITO memristor depend on both the a-GaOx layer itself and the a-GaOx/ITO junction. The fitting results indicate that the a-GaOx/ITO junction is Schottky with unidirectional conductive properties. However, the elevated defect density results in a larger current for the reverse-biased a-GaOx/ITO junction. Moreover, adjusting the thickness of a-GaOx allows the device to achieve almost symmetrical forward and reverse currents. We have successfully observed typical synaptic characteristics in W/WOx/a-GaOx/ITO when stimulated by consecutive spike signals. Clearly, through careful design considerations regarding the structure and parameters, we have realized superior synaptic performance in a-GaOx-based memristors. This achievement shows that amorphous GaOx has great potential applications in neuromorphic computation chips for artificial intelligence or the Internet of Things in the future.

Role of Mixed Oxidant and Controlled Oxygen Partial Pressure Heat Treatment to Regulate the Dielectric Properties and Resistivity of SrTiO3-based CP Ceramics

Sr0.99La0.01TiO3 (SLT10) colossal permittivity (CP) ceramic materials were synthesized using solid phase method and secondary heat treated using mixed oxidant 35%Bi2O3-10%Al2O3-20%MgO-25%CuO-10%SiO2 oxidant. The heat treatment atmospheres were chosen as O2, air, and Ar to correspond to different oxygen partial pressures. The dielectric properties of the Sr0.99La0.01TiO3-Percolated (SLT10-P) ceramics were investigated, and the contribution of the oxidant to the resistivity enhancement was verified by complex impedance spectroscopy and DC resistivity tests. Excellent dielectric properties were obtained for SLT10-P Air ceramic sample (16543 for dielectric permittivity and 0.016 for loss tangent), and the resistivity was increased from 2.13×108 Ω·cm (SLT10) to 1.23×1011 Ω·cm (SLT10-P Air). The resistance degradation mechanism of SLT10-P ceramics and oxygen vacancy migration in the process of resistance degradation were studied by using resistance monitoring device and thermally stimulated depolarization currents (TSDC) test. The introduction of oxidant optimizes the temperature stability and resistivity of SLT10 ceramics, but it will lead to the decrease of dielectric permittivity. The atmosphere of heat treatment changed the concentration of oxygen vacancy in ceramics. When SLT10-P O2 was treated in O2 atmosphere, the concentration of oxygen vacancy in ceramics decreased, which led to the decrease of dielectric permittivity and the increase of grain boundary resistance. For SLT10-P Ar ceramic, more oxygen vacancies and free electrons are induced by low oxygen partial pressure heat treatment, which enhances the dipole effect of electron pinning defects and leads to colossal dielectric permittivity, but high concentration of oxygen vacancies will affect the resistance decline. In SLT10-P Air ceramic, the coexistence of colossal permittivity and low loss tangent and high resistance is realized.

Double gradient coupling heterostructure design accurately regulates the anion process of the Li-rich cathode

Lithium-rich layered oxides are regarded as the next generation of cathode materials for lithium-ion batteries due to their high capacity and high operating voltage. However, the release of oxygen at high voltage has caused serious failure problems, severely limiting the commercial application of lithium-rich cathode materials. As the irreversible release of oxygen occurs first at the surface of the particles, the change in structure at the surface is also more drastic. In response to the variability of anion redox processes from surface to interior in the particles, a coupling strategy of Al, oxygen vacancies double gradient and spinel heterostructure was designed. The high concentration of oxygen vacancies and Al on the surface inhibits excessive oxidation of lattice oxygen and oxygen release. The surface heterostructure improves the reaction kinetics and increases the activity and reversibility of the electrode process. The concentration of oxygen vacancies and Al in the interior ensures highly active anionic redox and further enhances structural stability. The specific capacity (0.13 mAh/g/cycle) and voltage (1.34 mV/cycle) decay of the modified material is greatly reduced. In-situ and ex-situ characterisations were used to analyse the modification mechanism, which can effectively guide the improvement of lithium-rich cathode material performance.

Enhanced electro-catalytic activity of TNTs/SnO2-Sb electrode through the effect mechanism of TNTs architecture

The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.

Atomic‐Scale Engineering for New Generation Air Electrode Materials of Solid Oxide Cells: Quintuple Perovskite Sm2Ba3Co2Fe3O15‐δ with Twinned Crystal Structure

AbstractThe catalytic activity and thermomechanical stability of electrode materials are crucial for the efficient operation of reversible solid oxide cell (rSOC). However, these two traits often impose limitations on one another. In this work, a unique quintuple perovskite Sm2Ba3Co2Fe3O15‐δ (SBCF‐5L), comprising of A‐site ordered double perovskite layers and disordered simple perovskite layers, is reported as a high‐performance air electrode material for rSOC. The designed SBCF‐5L material exhibits a highly symmetrical tetragonal structure (pseudo‐cubic) with an isotropic thermal expansion and a limited chemical expansion. The formation barriers for oxygen vacancies are comparable between A‐site ordered layers and disordered simple perovskite layers, resulting in a high concentration of oxygen vacancies and 3D‐like bulk mobility of oxygen ions. Perpendicularly twinned nanodomains are developed in the particles, providing more active sites for surface electrode reaction. When applied in electrolyte‐supported cells, the SBCF‐5L electrode exhibits excellent electrochemical performance with low polarization resistance of 0.017 Ω cm−2, high power density of 1.01 W cm−2 and high electrolysis current density of 1.08 A cm−2 at 1.3 V at 800 °C in fuel cell and electrolysis modes, respectively. This study introduces a new approach of atomic‐scale engineering to rationally design a new generation of air electrodes for rSOC.

High-efficiency ZnO:Al/p-GaN epitaxial heterojunction photocatalysts for antimicrobial application

Highly efficient ZnO:Al (AZO) thin-film-type photocatalysts with thicknesses of approximately 400 nm are deposited on (0001) p-GaN at deposition temperature of 400 °C via cathodic arc plasma evaporation to develop epitaxial heterojunction photocatalysts for antimicrobial applications. AZO films with a multidomain structure are deposited on (0001) sapphire to compare their antimicrobial performances. Their microstructural and electrical properties, depth-resolved cathodoluminescence spectra, and antibacterial activity are investigated. The results of antimicrobial activity analysis indicate that the AZO/p-GaN heterojunction photocatalysts exhibit better antibacterial activity against Staphylococcus aureus than the multidomain AZO films deposited on (0001) sapphire. The improvement in antibacterial activity is attributed to the built-in electric field formed by the AZO/p-GaN heterojunction, which results in enhanced separation between photogenerated electrons and holes under ultraviolet A irradiation. In addition, the AZO/p-GaN heterojunction photocatalysts possess higher concentrations of oxygen vacancies, defect levels, conductivities, and carrier mobilities than the multidomain AZO films. Therefore, they exhibit better antibacterial activity by inhibiting the growth of S. aureus. An excellent antimicrobial thin film-type AZO/p-GaN epitaxial heterojunction photocatalysts is successfully developed in this study for application in the microbial control field.

The Enhanced Performance of Oxide Thin-Film Transistors Fabricated by a Two-Step Deposition Pressure Process.

It is usually difficult to realize high mobility together with a low threshold voltage and good stability for amorphous oxide thin-film transistors (TFTs). In addition, a low fabrication temperature is preferred in terms of enhancing compatibility with the back end of line of the device. In this study, α-IGZO TFTs were prepared by high-power impulse magnetron sputtering (HiPIMS) at room temperature. The channel was prepared under a two-step deposition pressure process to modulate its electrical properties. X-ray photoelectron spectra revealed that the front-channel has a lower Ga content and a higher oxygen vacancy concentration than the back-channel. This process has the advantage of balancing high mobility and a low threshold voltage of the TFT when compared with a conventional homogeneous channel. It also has a simpler fabrication process than that of a dual active layer comprising heterogeneous materials. The HiPIMS process has the advantage of being a low temperature process for oxide TFTs.

Structural Characterization of La0.6Sr0.4CoO3-δ Thin Films Grown on (100)-, (110)-, and (111)-Oriented La0.95Sr0.05Ga0.95Mg0.05O3-δ.

In this study, a detailed structural characterization of epitaxial La0.6Sr0.4CoO3-δ (LSC) films grown in (100), (110), and (111) orientations was conducted. LSC is a model air electrode material in solid oxide fuel and electrolysis cells and understanding the correlation of bulk structure and catalytic activity is essential for the design of future electrode materials. Thin films were grown on single crystals of the perovskite material La0.95Sr0.05Ga0.95Mg0.05O3-δ cut in three different directions. This enabled an examination of structural details at the atomic scale for a realistic material combination in solid oxide cells. The investigation involved the application of atomic force microscopy, X-ray diffraction, and high-resolution transmission electron microscopy to explore the distinct properties of these thin films. Interestingly, ordering phenomena in both cationic as well as anionic sublattices were found, despite the fact that the thin films were never at higher temperatures than 600 °C. Cationic ordering was found in spherical precipitates, whereas the ordering of oxygen vacancies led to the partial transition to brownmillerite in all three orientations. Our results indicate a very high oxygen vacancy concentration in all three thin films. Lattice strains in-plane and out-of-plane was measured, and its implications for the structural modifications are discussed.

Hybrid Approach for Modeling Memristive Elements

Typically, changes in the conductive properties of resistive random‐access memory elements happen due to the movement of ions in an ultra‐thin dielectric layer under the influence of an electric field. In the case of oxides, they often talk about the movement of oxygen vacancies and the formation/destruction of conducting filaments. Such processes are often described by dynamic systems in which the state parameter corresponds to the position of the boundary between regions with low and high concentrations of oxygen vacancies. In this case, the dependence of the current (or resistance) on the state parameter and the voltage applied to the element can be quite complex. In this regard, the work proposes an approach that uses neural networks to approximate the dependence of the current on the state parameter and voltage. Thus, a hybrid model is obtained in which the state parameter is determined using a dynamic system that takes into account the basic physical characteristics of the elements, and the model is finely tuned to the experimental data at the neural network level. A hybrid model for a memristor based on hafnium oxide (HfO2), as well as on nanocomposite (Co–Fe–B)m(LiNbO3)100−m, has been successfully constructed.

Sintering densification behavior of nano-ITO powder with high oxygen vacancy induced via plasma stimulation

With the growing electronics display industry, indium tin oxide (ITO) powder plays a crucial role in target preparation. To enhance the sintering performance of ITO powder, a high-activity nano ITO powder was prepared using plasma spraying, and compared to a commercial powder. This study aimed to investigate the effects of different preparation methods on powder morphology, dispersibility, oxygen vacancy concentration, and the physical properties of powders on target density, surface morphology, grain size, element distribution, and solid solubility. The results indicate that the plasma spraying high-activity nano ITO powder exhibits better dispersibility, higher oxygen vacancy concentration, and a specific surface area of up to 88.39m2/g compared to the commercial powder. Under normal pressure sintering conditions, plasma spraying nanoscale ITO powder exhibits higher sintering activity, leading to easier densification of ceramic targets with reduced porosity, more uniform surface grains, and significant stepped growth between surface grains. High-resolution transmission electron microscopy (HRTEM) analysis suggests that targets prepared with high-activity powder have greater tin solubility in indium oxide compared to traditional commercial ceramic targets. This article further explores the relationship between powder specific surface area, oxygen vacancy, and sintering activity, along with the formation mechanism of high oxygen vacancy.

Self-supported iron-doped nickel oxide multifunctional electrodes for highly efficient energy storage and overall water-splitting uses

Caused by complex synthesis processes, slow diffusion rates, and the formation of undesired nanostructures, it is tedious to produce a high-quality nickel oxide (NiO) electrodes for potential energy storage and water splitting applications. This paper introduces a novel chemical technique for producing self-supported iron-doped NiO electrodes having a high concentration of oxygen vacancies by utilizing different iron-based salts i.e. iron nitrate, iron chloride, iron ammonium sulfate, iron fumarate, and iron sulfate salts. After examining physical properties, the electrochemical energy storage and water splitting measurements were performed where iron nitrate precursor-mediated self-supporting Fe-NiO electrode confirms the optimum performance. Specifically, it exhibits a specific capacitance (SC) of 3302.5 Fg−1 at a current density of 5 Ag−1. The as-fabricated Fe-NiO-A//Bi2O3 asymmetric supercapacitor has a broad voltage range of 1.5 V, a remarkable volumetric-energy-density of 98.2 W hkg−1 at a power density of 900 Wkg−1, and a long-lasting cycling life with 92.6 % capacity retention after 5000 cycles at a current density of 15 Ag−1. A bifunctional Fe-NiO//Fe-NiO electrocatalyst demonstrates a current density of 10 mA cm−2 and remarkable long-term durability of 75 h without any degradation while operating at an ultra-low cell voltage of only 1.51 V, specifying importance of self-supported Fe-doped NiO electrodes for electrochemical energy storage and water splitting applications.

Enhanced CO2 methanation activity over Ni/CeO2 catalyst by adjusting metal-support interactions

CO2 methanation is an essential means of utilizing CO2, which is crucial to solving environmental problems and alleviating energy crisis. The design and development of high- performance low temperature CO2 methanation catalysts is the key to its further application. In this work, the metal-support interaction of Ni/CeO2 catalyst was regulated by changing the calcination temperature and Ni loadings to optimize the CO2 methanation performance. The results showed that 5NiCe-800 exhibited the best CO2 conversion of 83.1 % and 98.0 % CH4 selectivity at 350 °C, since it has a suitable Ni-CeO2 interaction, higher oxygen vacancy concentration, great reducibility and better basic site distribution. The reaction mechanism and the synergistic effect of CeO2 and Ni in CO2 methanation was revealed by in-situ FTIR, which is of great significance for the development of efficient CeO2 supported Ni-based for CO2 methanation.

Constructing Efficient CuAg Nanoalloys on Ce0.90In0.10Oδ for Methanol Deep Oxidation Catalysis at Low Temperature.

So far, it is still extremely challenging to develop an efficient catalyst for deep oxidation of methanol at low temperature. Herein, we report the construction of the highly dispersed CuAg alloy on the surface of Ce0.90In0.10Oδ nanorods support for catalyzing methanol deep oxidation. The composition, structure and properties of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the CuxAg100-x/Ce0.90In0.10Oδ alloy catalysts exhibit superior catalytic activity and stability compared to pure Ag/Ce0.90In0.10Oδ, with the highest activity observed for Cu40Ag60/Ce0.90In0.10Oδ, accompanied by the light-off temperature (T50) and full conversion temperature (T90) of 115 and 145 °C, respectively. This is attributed to the synergistic effect of CuAg alloy, which results in electron transfer, generating more Ag0, and enhanced interaction between CuAg alloy and the support, leading to increased Ce3+ content and higher oxygen vacancy concentration. This work successfully applies CuAg alloy catalysts in thermo-catalytic reaction, offering promising prospects for CuAg alloy catalysts in the methanol deep oxidation.

Fluorine-doped ATO NCs with enhanced LSPR effect for smart windows with adaptive solar modulation

Smart windows with excellent near-infrared (NIR) light shielding capacity and controlled visible light transmittance are expected to reduce building energy consumption and improve indoor comfort. However, the ability of current thermochromic materials to regulate solar gain with the tunable extinction of phase-change materials is still far from optimum. In this work, an fluorine (F)-doped ATO (FATO) nanocrystals (NCs) are designed as a photothermal material to optimize the solar modulation of thermochromic hydrogels. F ion doping can modify the electronic structure of ATO, resulting in a high concentration of oxygen vacancies and free electrons, thereby enhancing the NIR absorption performance and photothermal conversion performance of the ATO NCs. On this premise, the designed smart window based on FATO NCs and thermochromic hydrogels exhibits the remarkable features of excellent NIR shielding, high initial visible transmittance and fast response speed. The window is capable of shielding 99.5% of the solar radiation from 300 to 2500 nm and permitting 75.0% of initial visible light. Moreover, the simulated indoor temperature of the smart window was 17.2 °C lower compared with the black one, demonstrating potentials in practical application of building energy saving.

Fabrication of highly conducting undoped ZnO ceramics by flash sintering

Highly conducting undoped ZnO ceramics were fabricated by flash sintering using commercial pure ZnO powder as a model system. The flash-sintered samples with diameters of 15 mm and heights of 2 mm exhibited relative densities ranging from 93.6% to 97.1% and room-temperature electrical conductivities between 205 and 590 S/cm. X-ray diffraction and Raman spectra indicated a high concentration of oxygen vacancies and zinc interstitials in the flash-sintered samples, increasing the carrier concentration. Detailed microstructural analyses show that clean grain boundaries and the morphology and distribution of impurities in flash-sintered samples are favorable for improving carrier mobility. Additionally, flash sintering has the advantage of reducing conditions, which reduces acceptor defects at ZnO grain boundaries, lowers Schottky barriers, and increases carrier mobility. The results show that flash sintering can synergistically enhance the carrier concentration and mobility in ZnO ceramics, making it a promising technique for fabricating highly conducting ZnO ceramics.

Significantly enhanced oxygen vacancies in W18O49 nanowires for electrochromic films by annealing in argon

Owing to the energy-efficient attributes of electrochromic technology, there has been a growing emphasis on the fabrication of electrochromic devices with high-contrast and stable performance. As an electron donor, the deliberate incorporation of oxygen vacancies into an electrochromic material is poised to significantly elevate the film's electrochromic characteristics. In this study, we successfully synthesized one-dimensional W18O49 nanowires thin films with enhanced oxygen vacancies using a straightforward combination of solvothermal reactions and annealing in Ar. In comparison to films annealed in air, those treated in argon (Ar) exhibited a higher concentration of oxygen vacancies, resulting in improved light absorption characteristics. The optimal annealing conditions were determined to be 400 °C for 40 min. Under these conditions, the thin film demonstrates enhanced electrochromic performance, exhibiting a notable 71.6% modulation in transmittance, a 27.2% increase compared to the air condition. It displays a rapid response time (Tb = 3.3 s, Tc = 3 s), high coloration efficiency (CE = 55.9 cm2 C−1), and excellent cycling stability (with a ΔT retention rate of 93.9% after 750 cycles).

Ethanolamine gas sensors based on NdFeO3 modified hexagonal pyramid shaped ZnO nanocrystals

It is well known that two metal oxides can form depletion layers at the interface by constructing heterojunctions due to the different Fermi energy levels of each metal oxide, which can improve the carrier mobility and provide significant advantages for gas sensing. In this work, NdFeO3 nanoparticles were grown on ZnO with hexagonal cone structure by secondary hydrothermal method to successfully construct n-ZnO/p-NdFeO3 heterojunctions, and the crystal structures, oxygen vacancies, microstructures, optical properties, and gas-sensing properties of the ZnO/NdFeO3 composites were investigated. The ZnO/NdFeO3 sensors showed good ethanolamine (EA) The response characteristics of the ZnO/NdFeO3 sensor to ethanolamine (EA) with a concentration of 100 ppm EA at 240 °C (Rg/Ra) is about 25, which improves the response by a factor of 1.6 and 1.32 compared with that of NdFeO3 and ZnO. Meanwhile, it has excellent selectivity, good cyclic reproducibility, and durable long-term stability with response/recovery times of 19 s/49 s. The improved EA sensing performance of NdFeO3-modified ZnO, in addition to its large specific surface area due to its unique rough inhomogeneous structure, is also related to the higher concentration of oxygen vacancies at the ZnO/NdFeO3 interface after the composite. In addition, the construction of ZnO/NdFeO3 heterostructure brings more efficient carrier migration, which is favorable to the surface reaction and diffusion of EA molecules, and lowers the ZnO operating temperature, thus reducing the energy consumption. The ZnO/NdFeO3 composite sensor based on n-p heterojunction provides a valuable strategy for the detection of volatile organic compounds.

Solution Combustion Synthesis of Ce‐based Composite Oxygen Carriers for Chemical Looping Reforming of Methane

Efficient activation and the conversion of methane to value‐added products have long attracted interest. Chemical looping reforming has become a competitive technology to transform methane into syngas that can act as raw material for various chemicals. In this paper, the methane chemical looping reforming reactivity of the Ce‐Co composite oxygen carriers fabricated with different preparation methods, including solution combustion, ball‐milling, hydrothermal, and co‐precipitation method, are investigated on a fixed‐bed. Various bulk/surface characterizations (TEM, XRD, BET, XPS, Raman, etc.) were applied to reveal the effect of preparation methods on the properties of these oxygen carriers. The results indicate that the oxygen carrier prepared by the solution combustion method exhibits excellent methane conversion, high syngas yield, and desirable H2/CO ratio, as well as stable regenerability because of its relatively small crystal size, large specific surface area, high oxygen vacancy concentration and Ce3+/Ce4+ ratio. This work may be helpful in the preparation of highly active and stable oxygen carriers for chemical looping reforming reaction of methane.

Effect of dislocations on carrier recombination and photoelectrochemical activity in polished and unpolished TiO2 and SrTiO3 crystals

TiO2 and SrTiO3 are stable and efficient materials for photoelectrochemical (PEC) water splitting. PEC activity is influenced by carrier recombination in crystals of these materials. In this study, we analyzed the effect of dislocations on carrier recombination in TiO2 and SrTiO3 using microwave photoconductive decay measurements on polished and unpolished faces. The apparent slow decay in the unpolished face implies that dislocations trap minority carriers. Based on the different dependences of the injected photon density and temperature, the recombination processes in the polished and unpolished faces differ. A high concentration of oxygen vacancies or hydroxyl in the unpolished face of SrTiO3 was observed by x-ray photoelectron spectroscopy, and dislocations in the unpolished faces of both materials were observed using transmission electron microscopy. Additionally, we found that the photocurrent duration in the unpolished faces was shorter than that in the polished faces for both TiO2 and SrTiO3, confirming that dislocations inhibited photoelectrochemical activity.