(637b) Quantum Yield in a Photo-CREC Reactor for Hydrogen Production

Quantum Yield in a
Photo-CREC reactor for Hydrogen Production

Salvador Escobedo^a, Benito Serrano^b,
Hugo de Lasa^a,*

^a Western University, London, N6A 3K7, Canada

^b Universidad Autonoma de Zacatecas, Zacatecas, 98000,
Mexico

*Corresponding author: hdelasa@eng.uwo.ca

Introduction

         Nowadays, photoelectrodes and
photocatalysts are being developed for water splitting to produce hydrogen. The
goal of this study is to demonstrate the feasibility of water splitting for
hydrogen production through a Photo-CREC reactor, using a sacrificial agent and
a modified Platinum loaded semiconductor of DP25 (TiO₂) [1] It
is also the objective of this study determining optimum Pt loadings, as well as
quantum yields [2 and 3].

Experimental

Degussa P25 (TiO₂) was impregnated with
chloroplatinic acid. This step was followed by calcinations and reduction. A
2.7-2.85 eV reduced band gap was observed for the modified semiconductor using
UV-Vis NIR spectrophotometer (see Figure 1). The prepared Pt doped
photocatalysts were studied in a Photo-CREC-Water II. Macroscopic irradiation
balances were performed for establishing absorbed irradiated energy (see Figure
2) and quantum yields.

Figure 1. UV-Vis Band Gap

Figure 2. LVREA within the
Photo-CREC reactor using a macroscopic balance

Results and Discussion

Impregnation of Pt on TiO₂ leads to enhanced
particle size distribution with reduction of particle agglomeration (see Figure
3), with better distribution of charges on the semiconductor. On the other
hand, it is shown that Pt did not affect the anatase and rutile phases as well
as the specific surface area of the DP25. Figure 4 reports hydrogen production
as a function of contact time under free oxygen conditions and pH equals to 4.
Runs were developed with excess of Ethanol as OH^? scavenger reagent.
Hydrogen free
of oxygen was produced in all cases with 1wt% Pt on Degussa P25 yielding the
best hydrogen production rates. Figure 5 reports quantum yields in a 6-liter Photo-CREC reactor with
Ethanol at 2% v/v concentration and different Pt loads on Degussa P25 (see
Table 1). It is proven that Ethanol helps averting h⁺ and e^-
recombination, with the highest 7.86% quantum yields obtained between 1-6 hours of
irradiation.

Table 1 Reaction Rate at
different Loading of Pt on TiO₂ and pH=4

                                       ^a. Reaction
conditions: 298 K, 1 atm.

Figure 3. Particle Size
Distribution among different Catalyst

Figure 4. Hydrogen Production under pH=4,
Ethanol 2%v/v and Atmosphere of Argon.

Figure 5. Hydrogen Quantum Yield in
different catalyst

References

1. P. Alexia, K. Dimitris I. et al. Cat. today. 124 (2007) 94

2. B. Serrano, A. Ortiz, J. Moreira and H. de Lasa, Ind.
Eng. Chem.
Res.48
(2009) 9864

3. De Lasa Hugo, Serrano Benito
and Salaices Miguel, ?Photocatalytic Reactor Engineering?, Springer Science (2005),
pp 187; ISBN 0-387-23450-0