Shape-Dependent Reducibility of Cuprous Oxide Nanocrystals

In this paper the reducibility of octahedral and cubic Cu2O nanocrystals that respectively expose the (111) and (100) crystal planes has been investigated both experimentally and theoretically. Reduced either by H2 or CO, the reduction temperature of octahedral Cu2O nanocrystals is lower than that of cubic Cu2O nanocrystals by more than 120 °C, which provides the unambiguous experimental results that the Cu2O(111) crystal plane is much more facile to be reduced than the Cu2O(100) crystal plane. The DFT calculation results reveal that the different reducibilities of octahedral and cubic Cu2O nanocrystals arise from their different surface structures, in which the Cu2O(111) surface has coordination unsaturated Cu but the Cu2O(100) surface does not. The chemisorption and activation of CO and H2 are stronger on the Cu2O(111) surface than on the Cu2O(100) surface. These results provide the convincing evidence for the shape-dependent surface reactivity of oxide nanocrystals.