Photonic efficiency and selectivity study of M (M=Pt, Pd, Au and Ag)/TiO2 photocatalysts for methanol reforming in the gas phase

Abstract

A number of different M/TiO 2 photocatalysts, where M (the co-catalyst) = Pt, Pd, Au and Ag, are used to drive the steam reforming of methanol (MeOH) in a gas phase continuous flow reactor operated at 100 o C. The rate of H 2 production is: Pt > Pd > Au > Ag >> no metal. The photonic efficiency of Pt/TiO 2 photocatalyst is ca. 120% which suggests some of the hydrogen derives from a current-doubling reaction mechanism. The Pt/TiO 2 photocatalyst drives the steam reforming of MeOH, which generates H 2 and CO 2 , with an apparent selectivity of 100% over a wide UV irradiance range (i.e. 1-9.5 mW cm-2 at 365 nm). In contrast, in the dark, the decomposition of MeOH, which generates H 2 and CO, dominates with a selectivity of ca. 79%. In contrast to Pt, the Pd/TiO 2 photocatalyst is non-selective to either MeOH reforming or its decomposition, so that CO 2 and CO are generated with equal rates. The Au and Ag photocatalysts are less active than either the Pt or Pd co-catalysts and exhibit a variation in selectivity with UV irradiance which is intermediate between that of Pt and Pd. The possible use of photocatalysis as a means to generate H 2 from alcohol-based biofuels is briefly discussed.

Effect of the Microstructure of the Semiconductor Support on the Photocatalytic Performance of the Pt-PtOx/TiO2 Catalyst System

“…This rendered direct comparison of the catalytic properties of the bare TiO 2 materials impossible in this study. Otherwise, our hydrogen production results are of the same order as those in other works [ 13 , 57 , 58 , 59 ]. As can be seen from Figure 2 , the P25-based samples gave a higher H 2 production rate than the sol–gel-based samples, irrespectively if the Pt co-catalyst was formed by hydrogen reduction or calcination.…”

Photocatalytic Reforming for Hydrogen Evolution: A Review

“…However, as for the intrinsic properties of TiO 2 , especially the large band gap (>3.2 eV) restricts its utilization of the visible light and the high electron-hole recombination rate, its photocatalytic activity is significantly limited [39][40][41]. Michael et al reported on metal-modified TiO 2 applied in photocatalytic reforming of methanol [42]. Four different metals (Pt, Pd, Au and Ag) were selected to be combined with TiO 2 .…”

“…Products of photocatalytic reforming of methanol on different photocatalyst (no shading: H 2 , diagonal shading: CO 2 and vertical shading: CO, adapted from Ref [42]…”

Recent Developments of TiO2-Based Photocatalysis in the Hydrogen Evolution and Photodegradation: A Review

“…Another important application of TiO 2 -based photocatalysts is based on their ability to discolor and completely decompose organic dyes contained in water. In addition, there are a number of works in which TiO 2 -based photocatalysts were used to neutralize harmful to the atmosphere gases [ 6 , 7 , 8 , 9 ]. Chemical stability, easy accessibility, nontoxicity and the ability to oxidize under the influence of radiation, allow TiO 2 -based photocatalysts to solve the main global problems associated with pollution of the environment and need for renewable energy [ 10 , 11 ].…”