Surface-Alkalinization-Induced Enhancement of Photocatalytic H2 Evolution over SrTiO3-Based Photocatalysts

Recent advances in synthesis and applications of clay-based photocatalysts: a review

Clay-based photocatalysts with high adsorbability and special structures have attracted extensive attention because of their applications in environment and energy fields.

Role of oxygen impurity on the mechanical stability and atomic cohesion of Ta3N5 semiconductor photocatalyst

Hybrid-DFT calculations were performed to study effects of oxygen impurity on the mechanical stability and atomic cohesion in Ta₃N₅ photocatalyst.

A hybrid DFT based investigation of the photocatalytic activity of cation–anion codoped SrTiO3 for water splitting under visible light

The effect of cation (Mo or W) and anion (N) codoping in different proportion has been explored to improve the photocatalytic activity of SrTiO₃ under visible light. Codoping in 1 : 2 ratio has been found to be more effective due to reduction in band gap without introducing local trapping center and also for maintaining appropriate band alignment.

High alkalinity boosts visible light driven H2 evolution activity of g-C3N4 in aqueous methanol

A high rate of 2.23 mmol h⁻¹ g⁻¹ (quantum efficiency of 6.67% at 400 nm) for visible light driven photocatalytic H₂ evolution can be achieved with g-C₃N₄ by alkalization of the solution to a pH of 13.3, due to accelerated transfer of photoholes to the sacrificial donor.

Preparation of NiS/ZnIn2S4 as a superior photocatalyst for hydrogen evolution under visible light irradiation

In this study, NiS/ZnIn2S4 nanocomposites were successfully prepared via a facile two-step hydrothermal process. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Their photocatalytic performance for hydrogen evolution under visible light irradiation was also investigated. It was found that the photocatalytic hydrogen evolution activity over hexagonal ZnIn2S4 can be significantly increased by loading NiS as a co-catalyst. The formation of a good junction between ZnIn2S4 and NiS via the two step hydrothermal processes is beneficial for the directional migration of the photo-excited electrons from ZnIn2S4 to NiS. The highest photocatalytic hydrogen evolution rate (104.7 μmol/h), which is even higher than that over Pt/ZnIn2S4 nanocomposite (77.8 μmol/h), was observed over an optimum NiS loading amount of 0.5 wt %. This work demonstrates a high potential of the developing of environmental friendly, cheap noble-metal-free co-catalyst for semiconductor-based photocatalytic hydrogen evolution.

Template synthesis of single-crystal-like porous SrTiO₃ nanocube assemblies and their enhanced photocatalytic hydrogen evolution

Porous nanostructures of semiconductors are well-known for their ability to enhance the photocatalytic activity thanks to the large specific surface area and abundant active sites for the reactions, interfacial transport, and high utilization of light arising from multireflections in the pores. In this paper, we have successfully fabricated a special porous SrTiO3 three-dimensional (3D) architecture through a facile hydrothermal reaction at 150 °C, using layered protonated titanate hierarchical spheres (LTHSs) of submicrometer size as a precursor template. The SrTiO3 architecture is characterized by the 3D assembly of hundreds of highly oriented nanocubes of 60-80 nm by the partial sharing of (100) faces, thereby displaying porous but single-crystal-like features reminiscent of mesocrystals. Our experimental results have shown the key roles played by the template effect akin to that in topotactic transformation in crystallography and Ostwald-ripening-assisted oriented attachment in the formation of such nanocube assemblies. Compared to the solid SrTiO3 photocatalysts previously synthesized by high-temperature solid-state methods, the as-synthesized porous SrTiO3 nanocube assemblies have relatively large specific surface areas (up to 20.83 m(2)·g(-1)), and thus they have exhibited enhanced photocatalytic activity in hydrogen evolution from water splitting. Expectantly, our synthetic strategy using LTHSs as the precursor template may be extended to the fabrication of other titanate photocatalysts with similar porous hierarchical structures by taking advantage of the diversity of the perovskite-type titanate.

Leaf-architectured 3D hierarchical artificial photosynthetic system of perovskite titanates towards CO₂ photoreduction into hydrocarbon fuels

The development of an "artificial photosynthetic system" (APS) having both the analogous important structural elements and reaction features of photosynthesis to achieve solar-driven water splitting and CO₂ reduction is highly challenging. Here, we demonstrate a design strategy for a promising 3D APS architecture as an efficient mass flow/light harvesting network relying on the morphological replacement of a concept prototype-leaf's 3D architecture into perovskite titanates for CO₂ photoreduction into hydrocarbon fuels (CO and CH₄). The process uses artificial sunlight as the energy source, water as an electron donor and CO₂ as the carbon source, mimicking what real leaves do. To our knowledge this is the first example utilizing biological systems as "architecture-directing agents" for APS towards CO₂ photoreduction, which hints at a more general principle for APS architectures with a great variety of optimized biological geometries. This research would have great significance for the potential realization of global carbon neutral cycle.

Photoassisted fabrication of zinc indium oxide/oxysulfide composite for enhanced photocatalytic H2 evolution under visible-light irradiation

A photoassisted approach has been developed to synthesize a zinc indium oxide (Zn5In2O8)/oxysulfide composite through in situ sulfuration of vacancy-rich Zn5In2O8. It was found that vacancies have a considerable impact on the formation of the composite. The composite exhibited an increased photocatalytic H2 evolution activity under visible-light irradiation, which probably resulted from the enhanced ability to separate photoinduced electrons and holes. The H2 evolution rate over the composite was about 17 times higher when using vacancy-rich rather than conventional Zn5In2O8. This study provides a new method of improving the activity of photocatalysts.

Nanoscale strontium titanate photocatalysts for overall water splitting

SrTiO(3) (STO) is a large band gap (3.2 eV) semiconductor that catalyzes the overall water splitting reaction under UV light irradiation in the presence of a NiO cocatalyst. As we show here, the reactivity persists in nanoscale particles of the material, although the process is less effective at the nanoscale. To reach these conclusions, Bulk STO, 30 ± 5 nm STO, and 6.5 ± 1 nm STO were synthesized by three different methods, their crystal structures verified with XRD and their morphology observed with HRTEM before and after NiO deposition. In connection with NiO, all samples split water into stoichiometric mixtures of H(2) and O(2), but the activity is decreasing from 28 μmol H(2) g(-1) h(-1) (bulk STO), to 19.4 μmol H(2) g(-1) h(-1) (30 nm STO), and 3.0 μmol H(2) g(-1) h(-1) (6.5 nm STO). The reasons for this decrease are an increase of the water oxidation overpotential for the smaller particles and reduced light absorption due to a quantum size effect. Overall, these findings establish the first nanoscale titanate photocatalyst for overall water splitting.