KINETICS OF DISSOCIATIVE ADSORPTION OF FORMALDEHYDE ON A PT(111) ELECTRODE IN SULFURIC-ACID-SOLUTIONS STUDIED USING A PROGRAMMED POTENTIAL STEP TECHNIQUE AND TIME-RESOLVED FOURIER-TRANSFORM IR SPECTROSCOPY

The kinetics of dissociative adsorption of formaldehyde on Pt(111) ele ctrodes was investigated using a programmed potential step technique a nd in situ time-resolved Fourier transform IR spectroscopy (TR-FTIRS). We have demonstrated that the products of dissociative adsorption of HCHO on Pt(111) consist of both linear and bridge bonded CO. In contra st, the adsorption of CO from CO saturated solution yields only linear ly adsorbed CO species on this electrode. In the potential range betwe en -0.25 and 0.25 V the rate of dissociative adsorption of HCHO on Pt( 111) displays a volcano curve with two maxima located at -0.06 and 0.1 5 V respectively. The reaction rate maintains relatively high values b etween the two maxima. However, at potentials below -0.06 or above 0.1 5 V, the rate drops quickly towards zero. The initial rate ui of the d issociative adsorption of HCHO on Pt(111) was found to be on the order of 10(-11) mol cm(-2) s(-1). The TR-FTIRS studies confirmed the dynam ic properties of the dissociative adsorption of HCHO on Pt(111) electr odes.