Fig. 1

Characterisation of CeO2−x thin films. a Representative XRD pattern of a CeO2−x film deposited at a scan rate of 3000 mV s-1 for 1000 cycles. b XPS spectrum for Ce 3d orbital. c XPS spectrum for O 1s orbital. d HAADF image of nanostructure (scale bar is 2 nm). e EDS line scan across crystallite boundaries (left). f EDS line scan within crystallite (right). g EELS spectrum at crystallite boundary (point g). h EELS spectrum within crystallite (point h)