Evaluation of colloidal Os and Os-Alloys (Os-Sn, Os-Mo and Os-V) for electrocatalysis of methanol and borohydride oxidation

摘要

The oxidation of methanol and sodium borohydride (NaBH_4) on supported colloidal Os and Os-alloys (i.e. Os-Sn, Os-Mo and Os-V) have been studied by voltammetry and chrono-techniques (i.e., potentiometry, amperometry). The electrolytes were: 0.5 M H_2SO_4 for methanol oxidation and 2M NaOH (without and with 1.5 x 10~3 M thiourea (TU)) for borohydride oxidation, respectively. Voltammetry results showed that the investigated Os-based materials were catalytically inactive with respect to methanol oxidation, contradicting therefore, the theoretical suggestion by Kua and Goddard [J Am Chem Soc 1999; 121:10928-41] indicating electrocatalytic activity for Os toward methanol oxidation. Regarding the oxidation of borohydride, for direct borohydride fuel cells, preliminary results showed a voltammetric wave, with oxidation potentials between 0.1 and 0.3V vs. Ag/AgCl, KCl_(std), which were attributed to borohydride and TU oxidation. Chronopotentiometry results of Os-alloys showed a more positive operating potentials compare to colloidal Os catalysts.