Platinum on carbon-fibre paper catalysts for methanol electro-oxidation. Part 1.—Influence of activation conditions on catalytic activity

Abstract

The catalytic activity of platinum supported on specially pretreated carbon-fibre paper for the electro-oxidation of methanol is shown to be critically dependent on the atmosphere in which the catalyst is activated. The intrinsic activity of a catalyst activated in hydrogen is lower than that of one activated in air, even though the surface area of the platinum is larger after hydrogen activation. Furthermore, when hydrogen-activated catalysts are cycled potentiodynamically between 0 and 1.6 V, their activity increases considerably even though the surface area decreases.There are two possible explanations for this behaviour. Either the smaller crystallites of platinum are inherently less active than the larger ones produced by air oxidation followed by electrochemical reduction, or a metal–carbon interaction in hydrogen-activated catalysts is much weaker than that in the air-activated case. Either hypothesis can account for the effect of potentiodynamic cycling.