Surface metal modifiers for methanol electrooxidation on platinum; molybdenum and tungsten

S MARTINEZ; ME MARTINS; CF ZINOLA

ELECTROCHIMICA ACTA

ELSEVIER

Año: 2008

0013-4686

ABSTRACT New promising results on the electrocatalysis of methanol electrooxidation on platinum were found by combining various deposition methods with a second metal, i.e. molybdenum and tungsten. Apparently the nature of the second metal is important but also the deposition method. Although the electrochemical fingerprints of the resultant surfaces are similar, the morphology and electronic characteristics are different. These properties are responsible for the distinct catalytic activities toward methanol oxidation. The evaluation of the oxidation process was accomplished by potential sweep methods in bulk methanol solution together with the methanol residues anodic stripping profiles on both smooth platinum and columnar platinum modified by molybdenum and tungsten. The catalytic activity of the modified surfaces by spontaneous and electrochemical deposition was compared with that of smooth and columnar platinum. In the case of electrochemical deposition two preparation methods were chosen, potentiostatic or potentiodynamic. It is proposed a quasi-reversible process for the interaction between molybdenum and the platinum surface during both electrochemical depositions. The platinum surface modified by potentiodynamic deposition of molybdenum followed by tungsten presents the best performance upon methanol electrooxidation, recording at 0.7 V, a 50% higher current density than bare platinum. It was also found that the patinum/tungsten surface prepared by potentiostatic and potentiodynamic deposition, presents the lowest amount of carbon monoxide adsorbates.   Keywords: methanol electrooxidation; electrocatalysis; anodic stripping voltammetry; Pt-Metal electrodes; potentiodynamic deposition