ABSTRACT
Over the last decade, significant progress has been made to reinforce scanning electrochemical microscopy (SECM) as a powerful method for mechanistic studies of heterogeneous electron-transfer (ET) reactions. Various enabling technologies became available both experimentally and theoretically to quantitatively investigate heterogeneous ET reactions at the substrate (or tip) of SECM. High mass-transport conditions of nanoscale SECM requires the formation of a nanometer-wide gap between the tip and the substrate, which was enabled reliably by developing new technologies. The organic contamination of the HOPG surface was manifested by asymmetric limiting currents between feedback and SG/TC branches of nanoscale substrate voltammograms. The power of nanogap substrate voltammetry based on both feedback and SG/TC modes was also demonstrated by studying monolayer graphene grown by chemical vapor deposition (CVD). SECM-based nanogap voltammetry revealed the electrochemical transparency of monolayer graphene to find extremely fast ET kinetics at graphene supported by a polystyrene (PS) film.
