CO oxidation on nanoporous gold: A combined TPD and XPS study of active catalysts

► Catalytically active nanoporous gold was studied in UHV by XPS and TPD. ► Active and inactive surface oxygen species were identified on the catalyst surface. ► Active oxygen consumed by exposure to CO can be replenished by exposure to O2. ► CO2 evolution is linked to a CO desorption state at temperatures above 200 K. ► Residual silver and inactive oxygen may cause O2 activation and CO stabilization.