Lourdes Vázquez-Gómez

Preparation of 3D electrocatalysts and catalysts for gas-phase reactions, through electrodeposition or galvanic displacement

Metal foams are interesting supports for the preparation of electrocatalysts and catalysts for gas-phase processes, like partial and total low-temperature oxidation of hydrocarbons and other chemicals, owing to their large surface area, electrical conductivity, efficient mass and heat transfer, mechanical strength and resistance to oxidation. High catalytic activity in specific processes can be imparted to metal foams by the deposition of appropriately chosen noble metal nanoparticles. Deposition may be achieved electrochemically or through spontaneous deposition processes based on galvanic displacement reactions in which a noble metal displaces a less noble one. In the materials prepared by these methods, noble metal nanoparticles are in direct electrical contact with metal foams, so cyclic voltammetry may be effectively used to determine their surface area, a parameter of primary importance in heterogeneous catalysis. These features are illustrated by reviewing the preparation, characterization and catalytic testing of various noble-metal-modified Ni and Fe–Cr–Al alloy metal foams, highlighting advantages and limitations of the proposed methods, as compared with state of the art approaches.

Electrodeposition of Cu + PdO and ( Cu – Pd ) + PdO Composites

The codeposition of PdO particles with a Cu matrix has been investigated with the aim of extending the composite deposition procedure to the preparation of materials potentially capable of catalyzing the low temperature combustion of methane. Cu + PdO composites with a low dispersed phase content were obtained from either basic pyrophosphate or acid sulfate baths. Codeposition of PdO particles with a Cu-Pd alloy matrix was effectively achieved by electrolyzing suspensions of PdO in solutions containing both Cu 2+ and Pd 2+ ions, with large [Cu 2+ ]/[Pd 2+ ] ratios. (Cu-Pd) + PdO deposits with 20-25 Pd atom % were obtained in which only 1-2 atom % of Pd were alloyed in the matrix. These (Cu-Pd) + PdO composites were mechanically stable and highly porous throughout their thickness (their pore volume being ca. 60% of the total volume). Their true surface area was some thousands of times higher than their geometric area.