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 δ-gluconolactone was formed. Amperometric measurements provided a fixed 0.6 V value, showing high sensitivity (87.97 μA mM−1·cmRSA-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.