Synthesis of M/K4Nb6O17 nanosheet (M= Rh, Au,GO）for photocatalytic hydrogen evolution in a Z-scheme water splitting system

• Main Authors: Jin-Xiomg Yang, 楊錦雄
• Other Authors: Hsin-yu Lin
• Format: Others
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/69711434712149885183

碩士 === 國立東華大學 === 材料科學與工程學系 === 104 === In this study, we used solid state reaction to prepare K4Nb6O17. Then, we used exfoliation method to prepare the nanosheets photocatalyst, NS-K4Nb6O17(NSK). Au, Rh, Graphite oxide(GO) were loaded to NSK as cocatalyst. The photocatalysis activity for H2 evolution in a Z-scheme on M/K4Nb6O17 (M= Au, Rh, GO) photocatalyst is studied. Pt/WO3 was used as O2 evolution photocatalyst. And NaI solution was used as shuttle redox mediator. The light source was a 400W medium-pressure Halogen lamp. The reaction of Z-scheme photocatalysis overall water splitting system was 43oC. The catalysts were characterized by X-ray diffraction(XRD), UV-visible, Gas Chromatography(GC), transmission electron microscopy(TEM), electrochemical analyzer. First, Au nanoparticle was prepared by using C6H5O7Na3 to reduce HAuCl4. Different amount of C6H5O7Na3 could prepare different size of Au nanoparticle,17 nm, 33 nm,40 nm . Au(m)/NSK with diameters of 33 nm Au nanoparticle had the best photoactivity (H2: 486 O2: 225 (μmol g-1 h-1)). Second, pyramid Rh nanoparticle was prepared by Na3RhCl6 reduced by L-ascorbic acid in triethylene glycol solution with PVP protector. By controlling concentration of Na3RhCl6, L-ascorbic acid and reaction time, different of size pyramid Rh nanoparticle,14 nm,25 nm,55 nm could be prepared. The highest of photoactivity H2 evolution photocatalyst is Rh(m)/NSK (H2: 759 O2: 415 (μmol g-1 h-1))with diameters of 25 nm pyramid Rh nanoparticle. The Rh/NSK photocatalyst was prepared by adding Na3RhCl6 to exfoliation solution of NSK. The Rh/NSK photocatalyst exhibited a vary high photoactivity (H2: 4240 O2: 1622 (μmol g-1 h-1)). Furthermore, GO was loading to Rh/NSK to improve photoactivity. The 3%GO/Rh/NSK photocatalyst was prepared by adding GO and Na3RhCl6 to exfoliation solution of NSK, and showed a higher photoactivity (H2: 5430 O2: 2226 (μmol g-1 h-1)). IMP-5%GO/Rh/NSK was prepared by Impregnation method showed the highest H2 evolution rate (H2: 7623 ) but O2 evolution rate was lower (O2: 1913 (μmol g-1 h-1)). The best way to load GO on NSK is to add GO in the NaI solution. A-5%GO/Rh/NSK exhibited a highest photoactivity (H2: 7039 O2: 3289 (μmol g-1 h-1)).