Enhancement of photocatalytic activity of Gd(OH)3 nanoparticles by Pd deposition for reduction of CO2 to methanol

Photocatalytic degradation of brilliant green and 4-nitrophenol using Ni-doped Gd(OH)3 nanorods

Gadolinium hydroxide (Gd(OH)3) was synthesized via a microwave-assisted synthesis method. Nickel ion (Ni2+) was doped into Gd(OH)3, in which 4-12% Ni-Gd(OH)3 was synthesized, to study the effect of doping. The structural, optical, and morphological properties of the synthesized materials were analyzed. The crystallite sizes of the hexagonal structure of Gd(OH)3 and Ni-Gd(OH)3, which were 17-30 nm, were obtained from x-ray diffraction analysis. The vibrational modes of Gd(OH)3 and Ni-Gd(OH)3 were confirmed using Raman and Fourier-transform infrared spectroscopies. The band gap energy was greatly influenced by Ni-doping, in which a reduction of the band gap energy from 5.00 to 3.03 eV was observed. Transmission electron microscopy images showed nanorods of Gd(OH)3 and Ni-Gd(OH)3 and the particle size increased upon doping with Ni2+. Photocatalytic degradations of brilliant green (BG) and 4-nitrophenol (4-NP) under UV light irradiation were carried out. In both experiments, 12% Ni-Gd(OH)3 showed the highest photocatalytic response in degrading BG and 4-NP, which is about 92% and 69%, respectively. Therefore, this study shows that Ni-Gd(OH)3 has the potential to degrade organic pollutants.

Z-Scheme Heterojunction of SnS2/Bi2WO6 for Photoreduction of CO2 to 100% Alcohol Products by Promoting the Separation of Photogenerated Charges

Using sunlight to convert CO₂ into solar fuel is an ideal solution to both global warming and the energy crisis. The construction of direct Z-scheme heterojunctions is an effective method to overcome the shortcomings of single-component or conventional heterogeneous photocatalysts for photocatalytic CO₂ (carbon dioxide) reduction. In this work, a composite photocatalyst of narrow-gap SnS₂ and stable oxide Bi₂WO₆ were prepared by a simple hydrothermal method. The combination of Bi₂WO₆ and SnS₂ narrows the bandgap, thereby broadening the absorption edge and increasing the absorption intensity of visible light. Photoluminescence, transient photocurrent, and electrochemical impedance showed that the coupling of SnS₂ and Bi₂WO₆ enhanced the efficiency of photogenerated charge separation. The experimental results show that the electron transfer in the Z-scheme heterojunction of SnS₂/Bi₂WO₆ enables the CO₂ reduction reactions to take place. The photocatalytic reduction of CO₂ is carried out in pure water phase without electron donor, and the products are only methanol and ethanol. By constructing a Z-scheme heterojunction, the photocatalytic activity of the SnS₂/Bi₂WO₆ composite was improved to 3.3 times that of pure SnS₂.

Bi2MoO6 Quantum Dots In Situ Grown on Reduced Graphene Oxide Layers: A Novel Electron-Rich Interface for Efficient CO2 Reduction

Bi₂MoO₆ quantum dots (BM QDs, 5 nm in diameter) are evenly in situ grown on reduced graphene oxide (rGO) layers, sensitizing the graphene with high visible light response and activity for efficient solar light-driven CO₂ reduction. Under irradiation, small-sized BM QDs generate active electrons and donate them to the rGO layers. Since the formation of BM QDs and the reduction of GO are undergone simultaneously, a close connection between BM QDs and rGO enables the electron injection from excited Bi₂MoO₆ QDs to graphene scaffolds, and abundant electrons accommodated by the rGO layers offer an electron-rich interface for CO₂ reduction. With the benefit of the improved electron extraction and transport over the BM QDs/rGO interface, 84.8 μmol g^-1 of methanol and 57.5 μmol g^-1 of ethanol are achieved on BM QDs/rGO in 4 h with optimal composition. The total output of alcohols over BM/rGO (142.3 μmol g^-1) is 2.2 and 4.4 times that achieved on unmodified Bi₂MoO₆ QDs (64.0 μmol g^-1) and flower-like Bi₂MoO₆ (32.2 μmol g^-1), respectively.