Pushkar D. Kanhere

A Review on Visible Light Active Perovskite-Based Photocatalysts

Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance are reviewed in detail. Titanates, tantalates, niobates, vanadates, and ferrites form important photocatalysts which show promise in visible light-driven photoreactions. Along with simple perovskite (ABO3) structures, development of double/complex perovskites that are active under visible light is also reviewed. Various strategies employed for enhancing the photocatalytic performance have been discussed, emphasizing the specific advantages and challenges offered by perovskite-based photocatalysts. This review provides a broad overview of the perovskite photocatalysts, summarizing the current state of the work and offering useful insights for their future development.

Development of Sol–Gel Icephobic Coatings: Effect of Surface Roughness and Surface Energy

Sol-gel coatings with different roughness and surface energy were prepared on glass substrates. Methyl triethoxysilane (MTEOS), 3-Glycidyloxypropyl trimethoxysilane (GLYMO) and fluoroalkylsilane (FAS) were used to obtain a mechanically robust icephobic coating. Different amount of hydrophobic silica nano particles was added as fillers to introduce different roughness and surface energy to the coatings. The microstructure, roughness, and surface energy, together with elemental information and surface chemical state, were investigated at room temperature. The contact angle and sliding angle were measured at different temperatures to correlate the wetting behavior at low temperature with the anti-icing performance. The ice adhesion shear strength was measured inside an ice chamber using a self-designed tester. The factors influencing the ice adhesion were discussed, and the optimum anti-icing performance found in the series of coatings. It was found that lower surface energy leads to lower ice adhesion regardless of the roughness, while the roughness plays a more complicated role. The wetting behavior of the droplet on surface changes as temperature decreases. The anti-icing performance is closely related to the antiwetting property of the surfaces at subzero temperatures.

Dual-Phase Titanate/Anatase with Nitrogen Doping for Enhanced Degradation of Organic Dye under Visible Light

The need for environmental remediation processes on a large scale is becoming ever more urgent, especially in anticipation of the increasing demand (and potential shortage) of potable water supplies for a growing world population. Among the armory of advanced oxidation technologies (AOTs), photocatalytic (solar-light-driven) processes are particularly attractive, and photocatalysts have a well-demonstrated potential to mineralize harmful organic substances in air and water and even to act as regenerable adsorbents for toxic heavy metal ions, some of these being recovered as photodeposited metals. [1] Although anatase TiO2 remains the most popular photocatalyst due to high catalytic activity and chemical stability, there are some drawbacks associated with it. The activity is confined to UV-light stimulation, representing just a few percent of the solar-power spectrum. In this respect, much research has been done in modifying the bandgap of the material to extend the absorption into the visible-light region. [2] In addition, the adsorptive properties of TiO2 are not ideal either. [3] Since photoreactions take place at or near the catalyst surface, surface adsorption is critical for efficient interfacial charge transfer to and from the target molecules. In contrast, titanate materials have recently been identified as superior adsorbents for, for example, organic dyes and heavy metal ions. [4] The crystal structure consists of layers of TiO6 octahedra in edge connectivity with protons or alkali metal ions localized between the layers. [5] Various one-dimensional structures, including nano

Substitution induced band structure shape tuning in hybrid perovskites (CH3NH3Pb1−xSnxI3) for efficient solar cell applications

Organic–inorganic hybrid perovskite compounds such as CH3NH3PbI3 hold a great potential for low cost photovoltaic devices. Though CH3NH3PbI3 possesses fundamental properties favorable for solar energy harvesting, environmentally safe materials with higher energy efficiency are needed for practical applications. Replacement of lead by tin is a promising solution and investigating the fundamental properties of lead and tin mixed halides is essential. In this article, we have reported electronic and optical properties by employing Density Functional Theory based first principles calculations of Sn doped methyl ammonium lead halide, CH3NH3Pb1−xSnxI3 (x = 0, 0.25, 0.5, 0.75, 1.0). Our results reveal that tin doping narrows the optical band gap allowing absorption of visible light up to 850 nm. Tin doping at Pb sites primarily affects the composition and nature of the valence band maximum. Tin 5p induced electronic states are highly delocalized in nature and are likely to improve the mobility and possible exciton diffusion lengths of holes. Based on the results of this study, 50% Sn doping could to be useful for enhanced performance of perovskite based photovoltaics.

Li4x/3Co2−2xTi1+2x/3O4 spinel solid solutions: order and disorder phase transition, cations distribution and adjustable microwave dielectric properties

A series of spinel solid solutions Li4x/3Co2−2xTi1+2x/3O4 (LCT, 0.2 ≤ x ≤ 0.8) were synthesized and their structures and microwave dielectric properties were characterized in detail. The distribution of cations at A and B sites in the lattice has been analyzed by using Rietveld refinement. The microstructure and dielectric properties were studied by scanning electron microscope and microwave network analyzer. The solid solutions undergo a discontinuous B-site, Li/Ti order–disorder phase transition from a disordered cubic phase to an ordered cubic phase with increasing x values from 0.4 to 0.6. With increasing the A-site lithium content, the LCT ceramics exhibit improved dielectric permittivity er (20.3–26.5), high Q × f value (≥29 400 GHz) and a tailored temperature coefficient of resonant frequency τf from −40 to 10 ppm per °C. Optimized microwave dielectric properties were achieved for the composition with x = 0.8: er = 26.5, Q × f ≈ 29 400 GHz and τf ≈ 10 ppm per °C. A correlation between the cation distribution and microwave dielectric loss is discussed in detail.