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Cu/CeO2 electrocatalysts for H2 oxidation and O2 evolution reactions

The ceria-based transition metal (oxide) catalysts are known for their good redox characteristics. Depending on the reduction/oxidation state (level) they behave either as hydrogen storage (intermetallics) or as oxygen storage (mixed oxides) capacitors [Wrobel, G., Lamonier, C., Bennani, A. D'Huysser, A., Aboukaïs, A. J. Chem. Soc. Faraday Trans. 92 (1996) 2001]. The reduced transition metal (Cu) catalyst highly dispersed on CeO2 can undergo reversible oxidation at very low oxygen concentration in the reductive atmosphere already at room temperature. These findings have led us to the conclusion that it is worth to try this catalyst also in the electrochemical reactions, especially as the CO-resistant electro catalyst for hydrogen oxidation reaction (HOR) and as the electro catalyst for oxygen reduction reaction (ORR) in the low temperature PEM fuel cells.

The sol precursor of the nano-structured Cu/CeO2 electro catalyst was first obtained and mixed with Vulcan active carbon in order to prepare conductive substrate. After the appropriate activation procedure of this substrate, the Pt or Pt-Ru precursors were deposited on it in order to obtain a shell of noble metal over the core of Cu/CeO2. Thus , one of the preparation procedures for bi- and tri-metallic combinations supported on oxides and Vulcan have been used. The catalysts were subject to the detailed structural characterization and electrochemical tests. Based on tests with co-reduced and »onion«-type Pt-Cu catalysts and the characteristics of Cu/CeO2 support, we have obtained a new, CO-resistant electrocatalyst for low temperature PEMFC and DMFC.

The new Cu/CeO2 catalyst exhibits substantial electro catalytic activity in both, hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions. The gas diffusion electrode prepared with Cu/CeO2 catalyst behaves as the reversible electrode for hydrogen reactions (HOR and HER) with relatively high exchange current density. No copper dissolution is observed at anodic potentials that indicate important stabilisation of metallic copper when dispersed on CeO2 substrate. It shows no decay during potential sweep cycling in oxygen.

Reported by

National Institute of Chemistry
Hajdrihova 19
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