Study of PtOx/TiO₂ Photocatalysts in the Photocatalytic Reforming of Glycerol: The Role of Co-Catalyst Formation.

Katalin Majrik,Zoltán Pászti,Giuseppe Bonura,Catia Cannilla,László Korecz,Emília Tálas,Francesco Frusteri,László Trif,András Tompos,Attila Domján

doi:10.3390/ma11101927

Abstract

In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. This result was related to the negative effect of the adsorbed water content of the homemade TiO2 on Pt reduction and on particle growth during co-catalyst formation.

Highlights

Hydrogen is an important secondary energy source of the future [1,2,3] because it can be used in an environmentally friendly manner [4,5,6] and its chemical energy can be transformed to electricity very effectively by means of fuel cells
Our experiments pointed out that the answer should be the high water retention capacity of the PA TiO2, as proven by the thermogravimetricand and mass spectrometric evolved gas analyses (TG-MS) measurement: We found that after an additional vacuum treatment at 160 ◦ C before the high temperature N2 treatment, the photocatalytic activity on PAPtN2 tr (0.28 mmol × h−1 ) was similar to that on the PAPtH2 red sample (0.31 mmol × h−1 )
1 wt % Pt/TiO2 photocatalysts were prepared for photocatalytic reforming of glycerol on two very different supports, on P25, and on home-made high surface area TiO2 (PA)

Summary

Introduction

Hydrogen is an important secondary energy source of the future [1,2,3] because it can be used in an environmentally friendly manner [4,5,6] and its chemical energy can be transformed to electricity very effectively by means of fuel cells. Photocatalytic hydrogen production is a promising approach for transforming solar energy into chemical energy for storage [7]. Recent efforts indicate that photo-induced reforming of alcohols on semiconducting oxides in the presence of water may be an efficient way of solar energy based hydrogen generation [8,9]. Materials 2018, 11, 1927 increasing production of glycerol by-product, the use of glycerol as feedstock of photocatalytical reforming reaction would be an exciting possibility [10] (1): UV−Vis irradiation. Upon using aqueous solutions of glycerol at ambient conditions in the presence of Pt/TiO2 photocatalysts and a solar light-simulating source, it has been concluded that glycerol photoreforming may provide an efficient and low cost method for the production of renewable hydrogen [11]. While the conversion of the glycerol in the photocatalytic reforming reaction is of one or two-orders of magnitude less than that of other glycerol reforming systems at this moment, above reaction is widely studied and used as a model reaction to compare photocatalysts [12,13]

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