STEADY-STATE VOLTAMMETRY AT MICROELECTRODES FOR THE HYDROGEN EVOLUTION FROM STRONG AND WEAK ACIDS UNDER PSEUDO-FIRST AND 2ND-ORDER KINETIC CONDITIONS

The reaction of hydrogen evolution involving discharge of protons aris ing from strong and weak acids, namely perchloric, nitric, acetic, eth ylenediaminetetra-acetic and dihydrogen phosphoric acids, was investig ated in the concentration range 0.1-10 mM by steady state voltammetry at inlaid platinum micro-disc electrodes (of 10-12.5 mu m radius). ?Th e second-order CE mechanism for the weak acids was rationalised by dig ital simulation, demonstrating the effects of the various kinetic, the rmodynamic and diffusion parameters on the reduction process, In parti cular, it was found that proton reduction from acetic acid is associat ed with a completely mobile equilibrium over the whole concentration r ange studied, but in buffer solutions containing a large excess of the conjugate base the CE process becomes affected kinetically. For the o ther two weak acids the chemical step controls the kinetics at any con centration employed.