Disintegration of Flower-Like MoS₂ to Limply Allied Layers on Spherical Nanoporous TiO₂: Enhanced Visible-Light Photocatalytic Degradation of Methylene Blue

MoS₂/TiO₂ heterostructure with enhanced photocatalytic activity was successfully synthesized by hydrothermal method. The segmentation of flower-like MoS₂ structure resulted, during the hydrothermal condition in the presence of spherical nanoporous TiO₂ as a growing matrix. A pool of larger spherical TiO₂ particle induces a strain effect, which restricted the size of MoS₂. Meanwhile, the applied hydrothermal pressure leads the segmentation of the bundle-like structure of MoS₂ to individual layer. The obtained heterostructure was characterized by X-ray diffraction, Scanning, and Transmission electron microscopy, X-ray photoelectron spectroscopy, DRS-UV Visible spectra, Photoluminescence, Raman spectroscopy and BET surface area analysis. The photocatalytic activity of these synthesized materials was evaluated for the decomposition of methylene blue (MB) under visible light. The results indicated that MoS₂/TiO₂ heterostructure had higher photocatalytic activity than pristine MoS₂ and TiO₂ materials. After irradiation, the photocatalytic efficiency towards MB degradation was calculated as 67.4, 80.2 and 99.5% for MoS₂, TiO₂, and MoS₂/TiO₂, respectively. The formation of unique, distinct layers of MoS₂ over TiO₂ surface created more active sites for a photocatalytic response. These whole phenomena could enhance the absorption characteristics of dyestuff on the heterostructure and enhance the charge transport after conjugation, which improves MB degradation efficiency.

Enhanced Visible Light Activity of Pr-TiO₂ Nanocatalyst in the Degradation of Dyes: Effect of Pr Doping and TiO₂ Morphology

A facile hydrothermal method was adopted for the synthesis of bare TiO₂ and titania nanotubes (TNT). In an effort to increase the efficacy of the existing photocatalyst, different weight percentage (0.2, 0.4, 0.6, 0.8 and 1.0%) of praseodymium were deftly doped on to the synthesized titania scaffolds. The physicochemical characteristics of the architectured photocatalyst were thoroughly elucidated by various sophisticated techniques. The doping of Pr₂O₃ (Pr) on to titania nanotubes (TNT) resulted into a significant bathochromic/hyperchromic shift in the optical absorption edge (towards the visible region) as perceived from the DRS-UV spectra. The XRD and TEM analysis showed average crystallite size of the synthesised photocatalyst to be as small as 4-7 nm with well-formed nanotube framework. Photoluminescence spectra of Pr doped TNT catalyst clearly exhibited greater suppression of photogenerated electron-hole pair as compared to the undoped counterparts. The photocatalytic activity of the synthesized catalysts was evaluated towards the degradation of organic pollutants namely Rhodamine B (90%) and Crystal violet (93%) in the presence of solar light and its activity and durability was compared to that of commercial TiO₂ (Degussa P25). The observed enhanced photocatalytic activity of TNT and Pr-TNT can be unambiguously attributed to the inhibition of recombination of the electron-hole pairs due to doping of Pr into TNT. Among catalysts synthesized, 0.4 wt.% of Pr on to TNT yielded the highest photocatalytic activity under visible light irradiation.

3D nanorhombus nickel nitride as stable and cost-effective counter electrodes for dye-sensitized solar cells and supercapacitor applications

Transition metal nitride based materials have attracted significant interest owing to their excellent properties and multiple applications in the field of electrochemical energy conversion and storage devices. Herein we synthesize 3D nanorhombus nickel nitride (Ni₃N) thin films by adopting a reactive radio frequency magnetron sputtering process. The as-deposited 3D nano rhombus Ni₃N thin films were utilized as cost-effective electrodes in the fabrication of supercapacitors (SCs) and dye-sensitized solar cells (DSSCs). The structure, phase formation, surface morphology and elemental composition of the as-deposited Ni₃N thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM). The electrochemical supercapacitive performance of the Ni₃N thin films was examined by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) techniques, in 3 M KOH supporting electrolyte. The areal capacitance of the Ni₃N thin film electrode obtained from CV analysis was 319.5 mF cm⁻² at a lower scan rate of 10 mV s⁻¹. Meanwhile, the Ni₃N thin film showed an excellent cyclic stability and retained 93.7% efficiency of its initial capacitance after 2000 cycles at 100 mV s⁻¹. Interestingly, the DSSCs fabricated with a Ni₃N CE showed a notable power energy conversion efficiency of 2.88% and remarkable stability. The prominent performance of the Ni₃N thin film was ascribed mainly due to good conductivity, high electrochemically active sites with excellent 3D nano rhombus structures and high electrocatalytic activity. Overall, these results demonstrate that the Ni₃N electrode is capable of being considered for efficient SCs and DSSCs. This investigation also offers an essential directive for the advancement of energy storage and conversion devices.

Self-supported 3D nano-rhombus (nano-diamond) shaped Ni₃N coated on FTO glass which serves as a CE in DSSCs and supercapacitors. .

Selective oxidation of cyclohexane using Ce1-xMnxO2 nanocatalysts

The Ce1-xMnxO2 nanocatalysts (x = 0.25, 0.50 and 0.75 wt.%) were synthesized by sol-gel method. The catalysts were characterized using various techniques such as XRD, N2 sorption study, DRSUV-Vis, TPR, SEM and TEM. The incorporation of Mn ions into the ceria lattice was confirmed by XRD analysis. DRUV-Vis spectra confirm the presence of Ce3+ ions in the lattice of Ce1-xMnxO2. H2-TPR study revealed the oxygen storage capacity of the catalyst. The 3D flowerlike morphology of the nanocatalysts was confirmed from FESEM and HRTEM images. The catalytic activity was tested for the vapor phase oxidation of cyclohexane using air as an oxidant. The key reaction parameters were varied to study the stability, activity and selectivity of the catalysts. The study concluded that suitable amount of manganese content is essential for the selective oxidation of cyclohexane at low temperature and Ce0.25Mn0.75O2 is the most suitable catalyst for high conversion and selectivity under the given reaction conditions. The activity of the catalyst is correlated with the characterization results.