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

CuO and Cu 2 O powders were reacted by hydrogen to study the reduction mechanism and the ionic states of Cu (Cu 2+ , Cu 1+ and Cu 0 ). 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 ( ), under a normal flow of hydrogen. There was no hint of an intermediate state (Cu 1+ ) during the reduction. In certain conditions, however, an intermediate phase (Cu 2 O) appears under either very small flow of hydrogen (<1 cm 3 min −1 ) or very fast temperature ramping (>20 °C min −1 ), suggesting that the reduction kinetics strongly depends on reduction conditions.