Amorphous tantalum oxyhydroxide homojunction: In situ construction for enhanced hydrogen production

Photocatalytic kinetics of 2,4-dichloroaniline degradation by NiO-clinoptilolite nanoparticles

The ball-mill clinoptilolite nanoparticles (CNP) was ion-exchanged in Ni(II) solutions and calcined to obtain NiO-CNP catalysts with various NiO loadings. The resultant CNP was ion-exchanged in 0.1, 0.2, 0.3, and 0.4 M Ni(II) solutions and then calcined at 450 °C. The resultant NiO-CNPs contained 1.9, 2.3, 3.0, and 3.2% NiO, respectively. The XRD, FTIR, and DRS characterization techniques were applied. By applying the Scherrer equation on the XRD results, the average crystallite size for the NiO-CNP samples was estimated in the range of 42-65 nm. The pHpzc of the NiO-CNP species was slightly changed from 6.8 to 7.6 by an increase in the loaded NiO. The band gap energy of the samples was calculated by applying the Kubelka-Munk equation on the DRS results. The band gap energies of 3.81, 4.05, and 3.63 eV were estimated for the direct electronic transitions of the CN2, CN2.3, and CN3.2 samples, respectively. The boosted photoactivity was obtained in 2,4-dichloroanilyne (DCA) degradation when NiO supported onto both micronized clinoptilolite and its nanoparticles. The effects of the most important experimental variables on DCA photodegradation rate were kinetically studied by applying the Hinshelwood model on the results. The faster rate for the DCA photodegradation was achieved at the optimal conditions, including the catalyst dose: 0.5 g/L, C_DCA: 5 ppm, and the initial pH: 3. Some new peaks were observed in the HPLC chromatograms for the photodegraded DCA solutions after 180 min and 300 min, which showed 84% and 95% DCA photodegradation.

Alcohol solvothermal reduction for commercial P25 to harvest weak visible light and fabrication of the resulting floating photocatalytic spheres

In this study, to fabricate stable floating photocatalytic spheres, facile alcohol solvothermal reduction was first employed to modify commercial TiO₂ (P25) photocatalysts to harvest visible light and improve their performances for photodegrading phenol in seawater exciting by visible light. Floating photocatalytic spheres were then prepared by loading reduced P25 photocatalysts on inner and outer surfaces of acrylic hollow spheres. The structural characterizations showed that reduction of P25 introduced disorder–crystalline shell–core structures with present Ti³⁺ in reduced P25 photocatalysts. These features facilitated visible light response and phenol degradation in seawater under visible light irradiation. As reduction time or temperature of alcohol solvothermal process rose, more Ti³⁺ and shell–core structures were introduced into reduced P25, resulting in higher performances towards phenol degradation in seawater. However, extended periods of time and elevated temperatures decreased disordered layer of reduced P25, deteriorating the photocatalytic performances. Thanks to good light transmission of the hollow spheres and the high performance of the reduced P25, the photocatalytic performances of spheres loaded with reduced P25 could effectively degrade phenol in seawater even at low concentrations. The removal rate of phenol by floating spheres reached more than 95% after 8 h. In addition, the floating spheres displayed good stability and convenient reusability after six repeated photocatalytic degradation for phenol in seawater, promising features for future treatment of organic pollutants in oceans.

Remarkable Improvement in Photocatalytic Performance for Tannery Wastewater Processing via SnS2 Modified with N-Doped Carbon Quantum Dots: Synthesis, Characterization, and 4-Nitrophenol-Aided Cr(VI) Photoreduction

Photocatalytic pathways are proved crucial for the sustainable production of chemicals and fuels required for a pollution-free planet. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, the efficacy of the 0D N doped carbon quantum dots (N-CQDs) is demonstrated in accelerating the charge separation and transfer and thereby boosting the activity of a narrow-bandgap SnS₂ photocatalytic system. N-CQDs are in situ loaded onto SnS₂ nanosheets in forming N-CQDs/SnS₂ composite via an electrostatic interaction under hydrothermal conditions. Cr(VI) photoreduction rate of N-CQDs/SnS₂ is highly enhanced by engineering the loading contents of N-CQDs, in which the optimal N-CQDs/SnS₂ with 40 mol% N-CQDs exhibits a remarkable Cr(VI) photoreduction rate of 0.148 min^-1 , about 5-time and 148-time higher than that of SnS₂ and N-CQDs, respectively. Examining the photoexcited charges via zeta potential, X-ray photoelectron spectroscopy (XPS), surface photovoltage, and electrochemical impedance spectra indicate that the improved Cr(VI) photodegradation rate is linked to the strong electrostatic attraction between N-CQDs and SnS₂ nanosheets in composite, which favors efficient carrier utilization. To further boost the carrier utilization, 4-nitrophenol is introduced in this photocatalytic system and the efficiency of Cr(VI) photoreduction is further promoted.