RESUMEN
Cu nanoparticles (NPs) are low-cost surface plasmonic resonance (SPR) metal nanostructures, and their SPR properties can be used to enhance the photocatalytic hydrogen evolution performance of carbon nitride (C3N4). But their actual performance is usually limited, and one key factor is their poor interfacial quality. In this work, a highly conductive reduced graphene oxide (RGO) interlayer is introduced between protonated C3N4 (PCN) nanosheets and Cu NPs, which can act as an efficient sink for photogenerated electrons from C3N4 and hot electrons from Cu NPs, and simultaneously serve as reaction sites for the hydrogen evolution reaction, and accelerate the charge transport by the formed C-O-C and C-O-Cu bonds. The optimal hydrogen evolution rate of the optimized PCN/RGO/Cu is 1.30 mmol g-1 h-1, which is 6.76, 2.47 and 2.41 times that of PCN, PCN/RGO and PCN/Cu, respectively, and it can further reach up to 13.22 mmol g-1 h-1 by loading moderate Pt NPs. Meanwhile, the introduced RGO can effectively anchor Cu NPs to enhance the stability of the photocatalyst. In addition, due to the broad SPR response of Cu NPs, a near-infrared photocatalytic performance is realized for PCN/RGO/Cu with an apparent quantum efficiency of 0.46% at 765 nm.
RESUMEN
Low-cost and high-abundance Cu nanostructures are potential near-infrared (NIR) surface plasmonic resonance (SPR) photosensitizers for carbon nitride (C3N4) photocatalysts, but their low activity and stability need to be improved. In this article, doping S into C3N4 (S-C3N4) creates anchoring sites for photo-deposited Cu nanoparticles (NPs), and the spontaneous construction of S-Cu bonds is realized between S-C3N4 and Cu NPs. The optimal hydrogen evolution rate of 1.64 mmol g-1 h-1 is obtained for S-C3N4-Cu, which is 5.5, 4.6 and 1.7 times that of pure C3N4, S-C3N4 and S-C3N4-Cu, respectively. With further loading of a Pt co-catalyst to confirm the role of Cu NPs and improve the photocatalytic activity of the SCN-Cu, the photocatalytic rate can reach up to 14.34 mmol g-1 h-1. Due to the NIR SPR effect of Cu NPs, the apparent quantum efficiency (AQE) of S-C3N4-Cu at 600 and 765 nm is 2.02% and 0.47%, respectively. The enhanced photocatalytic performance of S-C3N4-Cu compared with C3N4-Cu is mainly due to the introduced S-Cu bonds that improve the injection rate of hot electrons. This solution provides a simple and efficient interface optimization strategy for the construction of efficient NIR-driven photocatalysts.
RESUMEN
The development of high-performance photocatalysts is central to efforts focused on taking advantage of solar energy to overcome environmental and energy crises. Integrating different functional materials artfully into nanostructures can deliver more efficient photocatalytic activity. Here, sandwiched ZnO@Au@CdS nanorod films were synthesized via successive ZnO nanorod electrodeposition, Au sputtering and CdS electrodeposition. The as-synthesized composites were characterized by UV-vis spectrophotometer, x-ray diffractometer, scanning and transmission electron microscopy. Their photocatalytic activity was assessed by degrading Rhodamine B solution under visible light irradiation. ZnO@Au@CdS exhibited better photocatalytic performance than ZnO@CdS throughout the visible light region, and the corresponding enhancement factor of Au nanoparticles was measured as a function of CdS loading amount, and it could reach 190% with CdS deposition for 1 min. The normalized rate constant could reach 0.387 h-1 for ZnO@Au@CdS-1min, which was equivalent to or better than results in reference photocatalysts. The enhancement mechanism of Au nanoparticles was estimated by comparing the monochromatic photocatalytic action spectra with the absorption spectrum of ZnO@Au@CdS, and it was mainly determined by incident photon energy. With selective excitation of Au nanoparticles by incident photons, the excited hot electrons in Au NPs are transferred to the conduction band of ZnO to boost photocatalytic reaction. With selective excitation of CdS, the enhanced interband absorption of CdS and relay station effect of Au nanoparticles should be responsible for the enhanced photocatalytic performance. Our work not only opens the door to the design of efficient supported photocatalysts, but also helps to understand the enhancement mechanism of LSPR effect on the photoelectric conversion of semiconductors.
RESUMEN
Sandwiched ZnO@Ag@Cu2O nanorod films were synthesized by successive electrodeposition, magnetron sputtering and the second electrodeposition. The as-synthesized composites were characterized by x-ray diffraction patterns, field emission scanning electron microscopy, low- and high-resolution transmission electron microscopy and a UV-vis spectrophotometer. Their photocatalytic performance was estimated by the degradation of a methyl orange solution under UV or visible-light irradiation, respectively. In the visible region, due to localized surface plasmon resonance absorption of Ag NPs, ZnO@Ag@Cu2O showed a significantly enhanced photocatalytic performance. The enhancement factor of Ag NPs on the catalytic performance of ZnO@Ag@Cu2O was estimated as a function of the Cu2O deposition time, and the corresponding enhancement mechanism was also evaluated by the monochromatic photocatalytic experiment and discrete dipole approximation simulation. In the UV region, due to the formation of a Schottky junction (e.g. Ag/ZnO, Ag/Cu2O), a limited enhanced photocatalytic performance was also realized for ZnO@Ag@Cu2O photocatalysts.
RESUMEN
One-step selective direct current (DC) plasma etching technology is employed to fabricate large-area well-aligned nanocone arrays on various functional materials including semiconductor, insulator and metal. The cones have nanoscale apexes (â¼2 nm) with high aspect ratios, which were achieved by a selective plasma etching process using only CH4 and H2 in a bias-assisted hot filament chemical vapor deposition (HFCVD) system without any masked process. The CH(3)(+) ions play a major role to etch the roughened surface into a conical structure under the auxiliary of H(+) ions. Randomly formed nano-carbon may act as an original mask on the smooth surface to initiate the following selective ions sputtering. Physical impinging of energetic ions onto the concave regions is predominant in comparison with the etching of convex parts on the surface, which is identified as the key mechanism for the formation of conical nanostructures. This one-step maskless plasma etching technology enables the universal formation of uniform nanocone structures on versatile substrates for many promising applications.
RESUMEN
The design of efficient visible-light-driven photocatalysts has become a hot topic due to their potential applications in energy and environmental industries. In this work, sandwiched ZnO@Au@Cu2O nanorod films were prepared on stainless steel mesh substrates in the order of the following steps: electrodeposition, sputtering, and second electrodeposition. The as-synthesized nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and UV-visible spectrophotometry, respectively. Due to their coaxial structure to inhibit the carrier recombination and the localized surface plasmon resonance effect of Au nanoparticles to enhance the visible light absorption, an outstanding visible-light-driven photocatalytic performance is realized. The enhancement magnitude of Au nanoparticles on the catalytic performance of ZnO@Au@Cu2O was estimated as a function of the Cu2O loading amount. The corresponding enhancement mechanism was also explained according to the photocatalytic results under monochromatic visible light irradiation, the active species trapping experiments, and discrete dipole approximation simulation results.