gabriel j. rodriguez rivera

-status-
Graduated

-research area-
Gold catalysis, catalysis with polyoxometalates

 -hometown-
Cidra, Puerto Rico

-undergraduate-
University of Puerto Rico – Mayaguez

 -publications-

"Catalytic Oxidation of CO by Aqueous Polyoxometalates on Carbon-supported Gold Nanoparticles", W. B. Kim, G. J. Rodriguez-Rivera, S. T. Evans, T. Voitl, J. J. Einspahr, P. M. Voyles, and J. A. Dumesic, submitted to the Journal of Catalysis.

"Hydrogenation of Benzene Using Aqueous Solution of Polyoxometalates Reduced by CO over Gold Catalysts", submitted, G. J. Rodriguez-Rivera, Won Bae Kim, S. T. Evans, T. Voitl, and J. A. Dumesic, submitted.

 “Powering Fuel Cells with CO via Aqueous Polyoxometalates and Gold Catalysts”, W. B. Kim, T. Voitl, G. J. Rodríguez-Rivera, J. A. Dumesic, Science 305, 1280 (2004)

“Preferential Oxidation of CO in H2 by Aqueous Polyoxometalates over Metal Catalysts”, W. B. Kim, T. Voitl, G. J. Rodríguez-Rivera, S. T. Evans, J. A. Dumesic, Angewandte Chemie Int. Ed. 44, 778 (2005)

~research summary~

CO Oxidation and Fuel Cell Power Generation via Aqueous Polyoxometalates and Gold Catalysts


            Production of H2 for fuel cells is usually accomplished by a multi-step process, starting with catalytic reforming of hydrocarbons or oxygenated hydrocarbons over metal catalysts to produce a mixture of H2, CO, and CO₂. These reformate gases are subsequently treated by several steps such as water-gas shift (WGS) (CO+H₂O --> CO₂+H₂).  Preferential oxidation of CO in the H2-rich gas stream (PROX) (CO+1/2 O₂ --> CO₂) is used for applications involving proton exchange membrane (PEM) fuel cells, due to the strong poisoning effects of CO on Pt-based anodes. While these methods for removing CO from H₂ gas stream are well established, they suffer from several limitations. For example, the WGS reaction is slow at the low temperatures (e.g., 500 K) required to achieve favorable thermodynamics for this reaction, and PROX requires the injection of O₂ (or air) into the H₂ gas stream and consumes a fraction of the H₂ as well.

Our research has focused on studying the CO oxidation over gold catalyst using aqueous solutions of polyoxometalates. The POMs used are strong oxidation agents which facilitate CO oxidation by liquid water at room temperature. High rates of CO oxidation were achieved at room temperature using aqueous solutions of polyoxometalates over carbon-supported gold catalysts. Gold catalysts has also showed higher rates for preferential oxidation of CO over hydrogen gas in hydrogen rich environments compared to other metal catalysts (i.e. Pt, Pd, Ir). Conventional processes for CO conversion often involve the use of Pt or Pt-alloy catalysts, which are expensive. These also compete with fuel cell electrodes for the limited supply of this precious metal, compared with the abundant holdings of gold in the world. The observed rates are faster than conventional processes operating at 500 K or higher for conversion of CO with water to produce hydrogen and carbon dioxide (via the water-gas shift, WGS). By eliminating the WGS reaction, we remove the need to transport and vaporize liquid water in the production of energy for portable applications. This process can utilize CO-containing gas streams from catalytic reforming of hydrocarbons to produce an aqueous solution of reduced polyoxometalate compounds that can be used to generate power. The reduced polyoxometalate can be re-oxidized in fuel cells containing simple carbon anodes.

Figure 1:  Diagram of CO oxidation - POM reduction over a gold nanotube catalyst

Figure 2: Schematic diagram of the membrane reactor coupled with fuel cells employed to study CO oxidation at the membrane reactor and energy transfer at the fuel cells.

-in collaboration with-
Won B. Kim, Tobias Voitl and Steven T. Evans

[members]     [research]     [facilities]     [publications]     [multimedia]     [press releases]