Oxygen Vacancy Injection on (111) CeO₂ Nanocrystal Facets for Efficient H₂O₂ Detection

Facet and defect engineering have achieved great success in improving the catalytic performance of CeO₂, but the inconsistent reports on the synergistic effect of facet and oxygen vacancy and the lack of investigation on the heavily doped oxygen vacancy keeps it an attractive subject. Inspired by this, CeO₂ nanocrystals with selectively exposed crystalline facets (octahedron, cube, sphere, rod) and abundant oxygen vacancies have been synthesized to investigate the synergistic effect of facet and heavily doped oxygen vacancy. The contrasting electrochemical behavior displayed by diverse reduced CeO₂ nanocrystals verifies that oxygen vacancy acts distinctly on different facets. The thermodynamically most stable CeO₂ octahedron enclosed by heavily doped (111) facets surprisingly exhibited the optimum non-enzymatic H₂O₂ sensing performance, with a high sensitivity (128.83 µA mM^-1 cm^-2), a broad linear range (20 µM~13.61 mM), and a low detection limit (1.63 µM). Meanwhile, the sensor presented satisfying selectivity, repeatability, stability, as well as its feasibility in medical disinfectants. Furthermore, the synergistic effect of facet and oxygen vacancy was clarified by the inclined distribution states of oxygen vacancy and the electronic transmission property. This work enlightens prospective research on the synergistic effect of alternative crystal surface engineering strategies.