Origin of highly efficient photocatalyst NiO/SrTiO3 for overall water splitting: Insights from density functional theory calculations

Controlled solvothermal synthesis of self-assembled SrTiO3 microstructures for expeditious solar-driven photocatalysis dye effluents degradation

In this work, the self-assembled SrTiO3 (STO) microstructures were synthesized via a facile one-step solvothermal method. As the solvothermal temperature increased from 140 °C to 200 °C, the STO changed from a flower-like architecture to finally an irregularly aggregated flake-like morphology. The photocatalytic performance of as-synthesized samples was assessed through the degradation of rhodamine B (RhB) and malachite green (MG) under simulated solar irradiation. The results indicated that the photocatalytic performance of STO samples depended on their morphology, in which the hierarchical flower-like STO synthesized at 160 °C demonstrated the highest photoactivities. The photocatalytic enhancement of STO-160 was benefited from its large surface area and mesoporous configuration, hence facilitating the presence of more reactive species and accelerating the charge separation. Moreover, the real-world practicality of STO-160 photocatalysis was examined via the real printed ink wastewater-containing RhB and MG treatment. The phytotoxicity analyses demonstrated that the photocatalytically treated wastewater increased the germination of mung bean seeds, and the good reusability of synthesized STO-160 in photodegradation reaction also promoted its application in practical scenarios. This work highlights the promising potential of tailored STO microstructures for effective environmental remediation applications.

Improved Thermoelectric Properties of SrTiO3 via (La, Dy and N) Co-Doping: DFT Approach

This work considers the enhancement of the thermoelectric figure of merit, ZT, of SrTiO₃ (STO) semiconductors by (La, Dy and N) co-doping. We have focused on SrTiO₃ because it is a semiconductor with a high Seebeck coefficient compared to that of metals. It is expected that SrTiO₃ can provide a high power factor, because the capability of converting heat into electricity is proportional to the Seebeck coefficient squared. This research aims to improve the thermoelectric performance of SrTiO₃ by replacing host atoms by La, Dy and N atoms based on a theoretical approach performed with the Vienna Ab Initio Simulation Package (VASP) code. Here, undoped SrTiO₃, Sr_0.875La_0.125TiO₃, Sr_0.875Dy_0.125TiO₃, SrTiO_2.958N_0.042, Sr_0.750La_0.125Dy_0.125TiO₃ and Sr_0.875La_0.125TiO_2.958N_0.042 are studied to investigate the influence of La, Dy and N doping on the thermoelectric properties of the SrTiO₃ semiconductor. The undoped and La-, Dy- and N-doped STO structures are optimized. Next, the density of states (DOS), band structures, Seebeck coefficient, electrical conductivity per relaxation time, thermal conductivity per relaxation time and figure of merit (ZT) of all the doped systems are studied. From first-principles calculations, STO exhibits a high Seebeck coefficient and high figure of merit. However, metal and nonmetal doping, i.e., (La, N) co-doping, can generate a figure of merit higher than that of undoped STO. Interestingly, La, Dy and N doping can significantly shift the Fermi level and change the DOS of SrTiO₃ around the Fermi level, leading to very different thermoelectric properties than those of undoped SrTiO₃. All doped systems considered here show greater electrical conductivity per relaxation time than undoped STO. In particular, (La, N) co-doped STO exhibits the highest ZT of 0.79 at 300 K, and still a high value of 0.77 at 1000 K, as well as high electrical conductivity per relaxation time. This renders it a viable candidate for high-temperature applications.

A review of advances in multifunctional XTiO3 perovskite-type oxides as piezo-photocatalysts for environmental remediation and energy production

Over more than three decades, the field of engineering of photocatalytic materials with unique properties and enhanced performance has received a huge attention. In this regard, different classes of materials were fabricated and used for different photocatalytic applications. Among these materials, recently multifunctional XTiO₃ perovskites have drawn outstanding interest towards environmental remediation and energy conversion thanks to their unique structural, optical, physiochemical, electrical and thermal characteristics. XTiO₃ perovskites are able to initiate different surface catalytic reactions. Under ultrasonic vibration or heating, XTiO₃ perovskites can induce piezo-catalytic reactions due to the titling of their conduction and valence bands, resulting in the formation of separated charge carriers in the medium. In addition, under light irradiation, XTiO₃ perovskites are considered as a new class of photocatalysts for environmental and energy related applications. Herein, we addressed the recent advances on variously synthesized, doped and formulated XTiO₃ perovskite-type oxides showing piezo- and/or photocatalytic exploitation in environmental remediation and energy conversion. The control of structural crystallite size and phase, conductivity, morphology, oxygen vacancy control, doping agents and ratio has a significant role on the photocatalytic and piezocatalytic activities. The different piezo or/and photocatalytic processes mechanistic pathways towards varying applications were discussed. The current challenges facing these materials and future trends were addressed at the end of the review.

Photoinduced electronic and ionic effects in strontium titanate

The interaction of light with solids has been of ever-growing interest for centuries, even more so since the quest for sustainable utilization and storage of solar energy became a major task for industry and research. With SrTiO₃ being a model material for an extensive exploration of the defect chemistry of mixed conducting perovskite oxides, it has also been a vanguard in advancing the understanding of the interaction between light and the electronic and ionic structure of solids. In the course of these efforts, many phenomena occurring during or subsequent to the illumination of SrTiO₃ have been investigated. Here, we give an overview of the numerous photoinduced effects in SrTiO₃ and their inherent connection to electronic structure and defect chemistry. In more detail, advances in the fields of photoconductivity, photoluminescence, photovoltages, photochromism and photocatalysis are summarized and their underlying elemental processes are discussed. In light of recent research, this review also emphasizes the fundamental differences between illuminating SrTiO₃ either at low temperatures (<RT) or at high temperatures (>200 °C), where in addition to electronic processes, also photoionic interactions become relevant. A survey of the multitude of different processes shows that a profound and comprehensive understanding of the defect chemistry and its alteration under illumination is both vital to optimizing devices and to pushing the boundaries of research and advancing the fundamental understanding of solids.