A Critical Evaluation of the Interpretation of Electrocatalytic Nanoimpacts

The kinetics of the proton reduction reaction is studied on a variety of gold surfaces including both macro (r(0) = 1.0 mm) and micro (r(0) = 4.6 mu m) electrodes, as well as gold nanoparticles (r(Np) = similar to 10 nm). For the gold nanoparticles, two complementary methodologies of study are used. First the particles are investigated as part of an ensemble response in an array (k(0) similar to 7 x 10(-8) m s(-1)). Second, the rate is recorded stochastically at individually impacting nanoparticles (k(0) similar to 2 X 10(-9) m s(-1)). This apparent decrease in reaction rates on transitioning from the ensemble to individual nanopartides is understood in terms of the differing connectivity of the nanoparticies to the electrode surface. During the course of the individual catalytic impacts, or pulses, the recorded current is found to be highly variable; this variability is interpreted as originating from the nanoscopic motion of the particle above the electrode interface.