Infrared spectra of surface nitrates: Revision of the current opinions based on the case study of ceria

•The classification of surface nitrates currently used by consensus is misleading.•Nitrates on ceria, thought to be monodentate, are actually tridentate.•Isotopic exchange with 18O helps distinguishing different nitrate coordination.•Bidentate nitrates on ceria are bridging and chelating simultaneously.•Bi/tridentate nitrates on ceria are converted to monodentate in presence of water.