Oxidation and reduction in copper/zinc oxides by mechanical milling

When zinc oxide is milled under vacuum or in the presence of oxygen, creati on of various types of defects results in an increased amorphous fraction, as well as higher surface area. Mechanochemical reactions occur when copper and copper oxides are milled together with zinc oxide: oxidation of copper and copper oxides take place in the presence of oxygen, whereas reduction takes place under vacuum. These reactions are promoted by the presence of Z nO. Formation of a Cu2O-like intermediate is suggested, which is not observ ed when milled without ZnO. The various resulting copper species reduce at different. temperatures in H-2 atmosphere. Both Cu-0 specific surfaces and BET surfaces are substantially increased for all milled Cu/ZnO samples, mal ring this method an interesting alternative for die preparation of promote d heterogeneous catalysts. (C) 2001 Elsevier Science B,V. All rights reserv ed.