Speaker
Mr
Andrew Chan
(The University of Auckland)
Description
Transition metal modified titania (M/TiO2, M = Pd, Pt or Au) photocatalysts have shown excellent activity for H2 production in alcohol-water mixtures under UV excitation [1, 2]. Recently, we have found that a 0.25 wt.% Pd-0.25 wt.% Au/TiO2 photocatalyst demonstrated a superior H2 production rate of 68 mmol g-1 h-1 compared to monometallic 0.50 wt.% Pd/TiO2 (43.0 mmol g-1 h-1) or 1.00 wt.% Au/TiO2 (34.2 mmol g-1 h-1) photocatalysts evaluated in 80 vol.% ethanol solutions at a UV flux (365 nm, 6.5 mW cm-2) comparable to that present in sunlight at the Earth’s surface. To rationalise the high H2 production activities of the Pd-Au/TiO2 photocatalysts, we characterize the materials using UV-Vis absorbance, TEM, XRD, XRF, N2 physisorption and lab-XPS. Preliminary data strongly suggests the formation of bimetallic Pd-Au nanoparticles on the surface of TiO2 responsible for the increased H2 evolution rates. Using higher resolution instrumentation, such as synchrotron XPS, XAS and HR-STEM, we further probed the question of ‘what is the Pd-Au nanoparticle structure (random, core-shell, ordered binary alloy)?’ Synchrotron Pd 3d and Au 4f XPS data (hν = 1486.7 eV) confirmed the presence of Pd(0)-Au(0), whilst HR-STEM/EDS showed Pd-Au nanoparticles of size 2-5 nm composed of randomly arranged Pd and Au atoms with a near 1:1 atomic ratio. Pd K-edge and Au L3-edge EXAFS analyses found the onset of alloy formation to occur around 160 °C in a 1 vol.% H2 atmosphere and nearest neighbour Pd-Au bond lengths of 2.08-2.35 Å were intermediate to that of Pd and Au metal in good agreement with HR-STEM data (Figure 1). Results here guide the rational design of new and improved M/TiO2 photocatalysts for H2 production.
![][1]
Figure 1. A-HRTEM, B-STEM-EDS, C-Pd and D-Au L3 FT-EXAFS.
References:
[1] Al-Azri, Z.H.N.; Chen, W.T.; Chan, A.; Jovic, V.; Ina, T.; Idriss, H.; Waterhouse, G.I.N. J.Catal. 2015, 329, 355-367.
[2] Chen, W.T.; Chan, A; Al-Azri, Z.H.N.; Dosado, A.G.; Nadeem, M.A.; Sun-Waterhouse, D.; Idriss, H.; Waterhouse, G.I.N. J.Catal. 2015, 329, 499-513.
[1]: http://noigraphics.heliohost.org/image.png
| Are you a student? | Yes |
|---|---|
| Keywords or phrases (comma separated) | Bimetallic, Pd, Au, titania, TiO2, Photocatalyst, XPS, TEM, XAS, EXAFS |
| Do you wish to take part in</br>the Student Poster Slam? | No |
| What is your gender? | Male |
| Are you an ECR? (<5 yrs</br>since PhD/Masters) | No |
Primary author
Mr
Andrew Chan
(The University of Auckland)
Co-authors
Dr
Dongxiao Sun-Waterhouse
(School of Chemical Sciences, The University of Auckland, New Zealand)
Dr
Geoffrey Waterhouse
(School of Chemical Sciences, The University of Auckland, New Zealand)
Prof.
Hicham Idriss
(SABIC, Corporate Research and Innovation (CRI), KAUST, Saudi Arabia)
