Self-assembly of structured CeCO3OH and its decomposition in H2 for a novel tactic to obtain CeO2-x with excellent photocatalytic property

In this work, various new-observed structured CeCO 3 OH were synthesized by a self-assembly hydrothermal method , and a novel tactic to produce CeO 2- x with excellent photocatalytic activity by decomposing CeCO 3 OH in H 2 was proposed and identified. By controlling the synthetic conditions, almond-like, subglobose shape and hollow-sphere of CeCO 3 OH, 3D-broom-like of Ce 2 O 3 · 2CO 2 · nH 2 O (n = (1–2)), and sheet-like of Ce 2 (CO 3 ) 3 · 6H 2 O were synthesized. The crystal growth and formation of the cerium carbonate compounds were carefully studied using XRD , SEM and TEM. TG, thermodynamic calculation and in-situ XRD were employed to reveal the decomposition behavior of almond-like CeCO 3 OH in air, Ar and H 2 . The results show that the decomposition temperatures of CeCO 3 OH in Ar and H 2 are higher than that of in air, and suggest that Ce 2 O 3 has a low thermodynamic stability during the decomposition of CeCO 3 OH in Ar and H 2 , and Ce 3+ will be mostly oxidized by H 2 O firstly and then by both of H 2 O and CO 2 . The ceria samples obtained by decomposing from CeCO 3 OH in different atmosphere maintain indistinguishable shape and particle size. The XPS , Raman spectra and ESR results indicate that the one obtained in H 2 has the richest surface oxygen vacancies (OVs), narrowest band gap of 3.12 eV, lowest intensity in PL spectra and a significantly enhanced photodegradation ratio of methylene blue. The MB photodegradation ratio after 120 min reaction with the catalysts of CeO 2 -Air, CeO 2 -Ar and CeO 2 -H 2 is 43.14%, 54.43% and 73.41%, with a calculated reaction rate constant of 0.00539, 0.00652 and 0.01097 min -1 , respectively. The offered novel tactic of decomposing CeCO 3 OH in H 2 is an efficient and facile technique for active CeO 2- x production.