Photochemical Construction of Ni/CdS Double‐Walled Magnetic Hollow Microspheres with Simultaneously Enhanced Visible‐Light Photocatalytic Activity and Recyclability

One-Step Photochemical Preparation of CdS/Poly(MMA-co-MAA) Composite with Enhanced Photocatalytic Activity

This paper presents a one-step photochemical method for the preparation of CdS/Poly(MMA-co-MAA) composite photocatalyst, based on the concept of simultaneous photocatalytic polymerization of organic monomers during UV-light induced formation of CdS. The preparation is carried out in an aqueous solution of Na2S2O3, CdSO4, methyl methacrylate (MMA) and methacrylic acid (MAA), under a UV lamp. The continuously formed CdS particles with photocatalytic activity act the role of initiator to directly initiate the copolymerization of MMA and MAA, resulting in the in situ formation of the composite and full contact of the CdS particles with the oxygen-containing groups in the polymer. Taking the photocatalytic degradation of methylene blue as a case study, the composite exhibited significantly higher activity under simulated solar light compared to the pure CdS. By analysis on various data, the enhanced photocatalytic activity is attributed to the enhanced visible light absorption, and especially the high electron-hole separation efficiency caused by the electrostatic interaction between photogenerated holes and carbonyl oxygen atoms with negatively charged features. Furthermore, the composite displays excellent sunlight activity and recyclability, suggesting its potential for practical applications. Such a one-step construction strategy relying only on photo-energy is green, low-cost and promising in obtaining high-performance semiconductor/polymer composite photocatalysts.

Graphene oxide nanosheets immobilised on honeycomb pore structure of pomelo peel for enhanced removal of methylene blue

Herein, for the first time, a simple, green, direct immersion immobilisation method is reported for graphene oxide (GO) nanosheets using pomelo peel (PL) as a substrate. A GO/PL porous sponge was successfully prepared and used to remove methylene blue (MB) from dye wastewater. Considering the porosity, hydrophilicity and elasticity of the PL, the PL was placed in a GO aqueous suspension through direct immersion immobilisation. The carboxyl and hydroxyl groups in the peel could effectively capture and immobilise the GO nanosheets. GO was adsorbed into the PL pores and dispersed throughout the PL. Finally, the prepared super-hydrophilic and elastic GO/PL exhibited excellent adsorption performance towards MB in dye wastewater. The adsorption results revealed that the adsorption behaviour was consistent with the Langmuir isotherm and quasi-secondary kinetic models. The maximum equilibrium adsorption capacity of GO/PL towards MB was 124.2 mg/g, exceeding the values obtained for most of the previously reported adsorbents. Moreover, after five consecutive adsorption-desorption cycles, GO/PL retained 75% of its initial adsorption capacity. Mechanistic analysis revealed that pore filling, electrostatic attraction, ion exchange and hydrogen bonding interactions are the primary driving forces facilitating MB adsorption.

Biotemplated CdS Nano-Aggregate Networks for Highly Effective Visible-Light Photocatalytic Hydrogen Production

In the last few decades, many new synthesis techniques have been developed in order to obtain an effective visible-light responsive photocatalyst for hydrogen production by water splitting. Among these new approaches, the biotemplated synthesis method has aroused much attention because of its unique advantages in preparing materials with special morphology and structure. In this work, Hydrilla verticillata (L. f.) Royle was used as a biotemplate to synthesize a CdS photocatalyst. The as-synthesized sample had the microstructure of nano-scaled aggregate networks and its activity for photocatalytic hydrogen production was six times higher than that of CdS synthesized without a template in an Na₂S-Na₂SO₃ sacrificial system. The use of Pt and PdS as cocatalysts further improved the hydrogen production rate to 14.86 mmol/g·h under visible-light (λ ≥ 420 nm) irradiation, so the hydrogen production can be directly observed by the naked eye. The results of characterization showed that the as-synthesized CdS photocatalyst has a high specific surface area and narrow band gap, which is favorable for light absorption and photocatalytic reaction. This work provides a new way to search for efficient visible-light catalysts and confirms the uniqueness of a biotemplated synthesis method in obtaining specially structured materials.