Specific activities of rhombic dodecahedral, octahedral, and cubic Cu2O nanocrystals as glucose oxidation catalysts

The specific properties, in terms of real surface area (RSA), of (1 1 0)-faceted rhombic dodecahedral (RD), (1 1 1)-faceted octahedral (OCT), and (1 0 0)-faceted nanocube (NC) Cu2O crystals as D-glucose oxidation catalysts were studied. Tafel measurements showed the activation energy of the RD catalyst (65.4 KJ mol(-1)) was lower than the energies of the OCT and NC catalysts (91.8 and 97.4 KJ mol(-1), respectively). Due to the facile surface oxidation of CuO, the RD catalyst showed an early rest potential of - 0.228 V (vs. Ag/AgCl, 3 M KCl), and had a much higher specific activity (0.253 mA cm(-2)) at 0.6 V compared to the OCT and NC catalysts (0.11 and 0.09 mA cm(-2), respectively). The glucose oxidation reaction (GOR) catalyzed by the RD crystals occurred via a two-electron mechanism, in which delta-gluconolactone was formed. Amperometric measurements provided a fixed 0.6 V value, showing high sensitivity (87.97 mu A mM(-1).cm(RSA)(-2)) within a linear analysis range of 0.1-8.4 mM. The high activity of the RD catalyst may originate from the coexistence of oxygen and cuprous ions on its outer plane, and its facile surface oxidation to CuO.