Tuning the Deoxygenation of Bulk-Dissolved Oxygen in Copper

Using synchrotron-based ambient-pressure Xray photoelectron spectroscopy, we report the tuning of the deoxygenation process of bulk dissolved oxygen in copper via a combination of H-2 gas flow and elevated temperature. We show that a critical temperature of similar to 580 degrees C exists for driving segregation of bulk dissolved oxygen to form chemisorbed oxygen on the Cu surface, which subsequently reacts with hydrogen to form OH species and then H2O molecules that desorb from the surface. This deoxygenation process is tunable by a progressive stepwise increase of temperature that results in surface segregation of oxygen from deeper regions of bulk Cu. Using atomistic simulations, we show that the bulk-dissolved oxygen occupies octahedral sites of the Cu lattice and the deoxygenation process involves oxygen migration between octahedral and tetrahedral sites with a diffusion barrier of similar to 0.5 eV.