The kinetics of the reduction of protons at polycrystalline and monocrystalline gold electrodes

Abstract

Abstract The reduction of H+ from 1 M HClO4 and 1 M NaClO4 solutions at polycrystalline and single crystal faces of very pure gold electrodes is studied by determining the forward rate constant kt as a function of potential and of H+ concentration. The techniques applied are dc current and impedance measurements both with a step-wise variation of dc potential (duration 4 s), and dc current measurements with a continuous potential variation. The consistency of the results is extensively tested and found to be quite satsifactory. Plots of 1n kt vs. potential are curved and exhibit limiting slopes corresponding to values for the operational transfer coefficient α = 1 positive and α = 0.5 at negative potentials. This behavior is discussed in terms of mechanistic models described in the literature and also an altenative mechanism is tentatively proposed. An increase in the rate constants is observed when the purity of the gold is less. The slight differences in the rate constants observed at single crystal faces of the same purity but with different crystallographic orientation are discussed.