Highly active Z-scheme heterojunction photocatalyst of anatase TiO2 octahedra covered with C-MoS2 nanosheets for efficient degradation of organic pollutants under solar light.

The construction of a Z-scheme photocatalyst by coupling semiconductors with conductors is an efficient way to achieve high pollutant degradation efficiency. In this study, a hydrothermal approach was used to fabricate a Z-scheme photocatalyst consisting of C-MoS2 sheets wrapped around octahedral anatase TiO2 nanocrystals. The catalyst showed excellent photocatalytic efficiency (99%) for methylene blue degradation with low catalyst loading (0.2 g L-1) under the simulated solar light within 60 min. High photocatalytic degradation efficiencies were also observed for Rhodamine B, methyl orange, and tetracycline under solar irradiation. The C-MoS2 acts as an electron mediator and serves as a carrier transmission bridge for the efficient electron-hole separation. The electron-rich (101)-faceted TiO2 benefits the Z-scheme recombination of electrons from the conduction band of TiO2 and holes at the valence band of MoS2. The semiconductor coupling of (101)-exposed octahedral TiO2 and 2H-MoS2 as well as the introduction of solid-state electron mediators, 1T-MoS2 and carbon, resulted in increased light absorption and accelerated charge transfer at the contact interface, which enhanced the photocatalytic activity of the photocatalyst significantly compared to those of P25, MoS2/TiO2, and C-MoS2. The efficient separation of electron-hole pairs prolongs their lifetime for oxidation and reduction reactions in the degradation process.

Self-templated hollow nanospheres of B-site engineered non-stoichiometric perovskite for supercapacitive energy storage via anion-intercalation mechanism.

The continual increase in energy demand and inconsistent supply have attracted attention towards sustainable energy storage/conversion devices, such as electrochemical capacitors with high energy densities and power densities. Perovskite oxides have received significant attention as anion-intercalation electrode materials for electrochemical capacitors. In this study, hollow nanospheres of non-stoichiometric cubic perovskite fluorides, KNi1-xCoxF3-δ (x = 0.2; δ = 0.33) (KNCF-0.2) have been synthesized using a localized Ostwald ripening. The electrochemical performance of the non-stoichiometric perovskite has been studied in an aqueous 3 M KOH electrolyte to categorically investigate the fluorine-vacancy-mediated charge storage capabilities. High capacities up to 198.55 mA h g-1 or 714.8 C g-1 (equivalent to 1435 F g-1) have been obtained through oxygen anion-intercalation mechanism (peroxide pathway, O-). The results have been validated using ICP (inductively coupled plasma mass spectrometry) analysis and cyclic voltammetry. An asymmetric supercapacitor device has been fabricated by coupling KNCF-0.2 with activated carbon to deliver a high energy density of 40 W h kg-1 as well as excellent cycling stability of 98% for 10,000 cycles. The special attributes of hollow-spherical, non-stoichiometric perovskite (KNCF-0.2) have exhibited immense promise for their usability as anion-intercalation type electrodes in supercapacitors.

Eco-friendly synthesis of recyclable mesoporous zinc ferrite@reduced graphene oxide nanocomposite for efficient photocatalytic dye degradation under solar radiation.

Zinc ferrite and graphene composites have attracted considerable attention in wastewater treatment. In this work, a magnetically separable mesoporous composite of ZnFe2O4 nanoparticles (NPs) and reduced graphene oxide (rGO) was prepared through a simple and eco-friendly method with pure water as solvent and without the need for subsequent thermal treatment. Uniformly dispersed ZnFe2O4 NPs on the surface of rGO sheets exhibited good crystallinity and a large BET specific surface area. These factors contributed to good photocatalytic performance of the composite for the degradation of methylene blue (MB) under simulated solar-light radiation, increased adsorptivity, increased separation efficiency of the photo-excited charges on the surface of the catalyst, and broadened light-absorption range of the composite. Efficient interfacial interaction between the ZnFe2O4 NPs and rGO sheets resulted in synergistic effects. The magnetically separable ZnFe2O4@rGO nanocomposite proved an efficient and stable catalyst in three consecutive photodegradation cycles for MB dye in aqueous solution under solar radiation. In addition, the synthesis method proposed in this study could be scaled-up easily due to the simplicity of the process, the lack of a toxic reagent, and the use of low temperatures.