SCANNING ELECTROCHEMICAL MICROSCOPY .33. APPLICATION TO THE STUDY OF ECE DISP REACTIONS/

The scanning electrochemical microscope (SECM) is used to measure the kinetics of ECE/DISP type reactions. The theory of the steady-state fe edback response is developed in terms of numerical simulation. The the oretical curves show that the variation of the tip and substrate curre nt with the tip-substrate separation can readily be used to differenti ate between an ECE and a DISP1 pathway. The theoretical results sugges t that rate constants up to 1.6 x 10(5) s(-1) can be measured with tip sizes usually employed in SECM. The theory is validated using the exp erimental example of the reduction of anthracene in DMF in the presenc e of phenol. The reaction is shown to follow a DISP1 pathway, in agree ment with previous studies. Good agreement is found between theory and experiment for all the phenol concentrations explored, and a rare con stant of (4.4 +/- 0.4) x 10(3) M(-1) s(-1) has been determined for the protonation of the anthracene radical anion by phenol.