Formation of Confined Platinum-Nanoparticles in PTA-Embedded Silica Channels for Photocatalytic Hydrogen Production
張哲瑋1, 賴英煌2, 鄭有舜1,3*
1Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan
2Department of Chemistry, Tunghai University, Taichung, Taiwan
3National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* Presenter:鄭有舜

Photocatalytic hydrogen production is one of the attractive renewable energy technologies without carbon dioxide emissions. Here, we report a one-step fabrication process of photocatalytic films comprising Pt-nanoparticles formed inside MCM41 channels at the air-liquid interface. Using in situ grazing incidence small-angle X-ray scattering (GISAXS), we monitor the film formation process from the formation of PTA embedded mesostructured silica (PMS) film self-assembled at the air-water interface. Pt precursor (chloroplatinic acid) is then added into the solution for self-adsorption into the silica channels of the PMS film, via anion exchange with the CTAB surfactant micelles. Upon UV irradiation, Pt-NPs can form gradually and homogeneously inside the 2D-hexagonally packed silica-surfactant channels by PTA-site-directed reduction, as revealed by the highly ordered and oriented GISAXS patterns. From the time-resolved GISAXS data, formation process is revealed. Transmission electron microscopy further evidences the arrayed Pt NPs directed by the 2D hexagonal lattice of the PMS channels with inter-channel spacing of 3.2 nm. Consistently, thermogravimetric analysis (TGA) reveals a significant PT weigh ratio of the Pt-NPs@PMS film, which is found to correlate with the ratio of PTA embedded in the PMS film. The hence formed Pt-NPs are confined together with photocatalytic PTA inside the PMS channels, which confined environment can facilitate greatly photo-electrons transfer to surface of Pt-NPs for hydrogen production and enhanced charge separations, upon light illumination. Moreover, with the channel confinement, aggregation of the bare-surface Pt nanoparticles of ca. 2 nm is greatly suppressed. As a result, the Pt-NPs@PMS composite exhibits prominent photocatalytic hydrogen production with isopropanol as sacrificial reagents under 300W Xe lamp. Nearly 10 time higher hydrogen production rate of 6520 μmol/g·h is achieved with Pt-NPs@PMS, compared to the neat PMS of no Pt nanoparticles.

Keywords: Photocatalytic hydrogen production, Platinum-Nanoparticles, Mesostructured Silica, Grazing-Incidence Small-Angle X-Ray Scattering