Reaction of CuO with hydrogen studied by using synchrotron-based x-ray diffraction

CuO and Cu2O powders were reacted by hydrogen to study the reduction mechanism and the ionic states of Cu (Cu2+, Cu and Cu). The reduction behaviour and the existence of an intermediate state were investigated by using synchrotron-based high-resolution in situ x-ray diffraction (S-XRD) techniques. The results revealed that CuO directly reduces to metallic Cu (Cu → Cu), under a normal flow of hydrogen. There was no hint of an intermediate state (Cu) during the reduction. In certain conditions, however, an intermediate phase (Cu2O) appears under either very small flow of hydrogen (<1 cm3 min−1) or very fast temperature ramping (>20 ◦C min−1), suggesting that the reduction kinetics strongly depends on reduction conditions. (Some figures in this article are in colour only in the electronic version)