Hydrogen diffusion in ceria: solid state NMR, combined scattering and spectroscopic studies, and ab initio calculations

Zhichao Zhu; Xin Li; Ziru Ma; Yuanhua Xia; Ruizhi Qiu; Baijiang Lv; Guanyun Yan; Jianrong Zeng; Long Yang; Jianbo Ma; Benqiong Liu; Guangai Sun

arXiv · 2506.08789

Hydrogen diffusion in ceria: solid state NMR, combined scattering and spectroscopic studies, and ab initio calculations

Zhichao Zhu·Xin Li·Ziru Ma·Yuanhua Xia·Ruizhi Qiu·Baijiang Lv·Guanyun Yan·Jianrong Zeng·Long Yang·Jianbo Ma·Benqiong Liu·Guangai Sun

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Abstract

Ceria has been extensively studied since it has many applications in diverse research fields. However, the mechanism of the hydrogen dynamics, especially the diffusion kinetics on a microscopic level is still unclear as the experimental data has been very limited. In this work, the CeO$_2$-H interaction has been comprehensively studied by a combination of $^1$H NMR transverse relaxation time ($T_2$) measurement, neutron powder diffraction, quasi-elastic neutron scattering (QENS), X-ray total scattering, and ab initio calculations. Based on QENS measurements, the first direct evidence for hydrogen jump diffusions of the Chudley-Elliot type in the bulk ceria has been given, with a jump distance of ~3.98 angstrom. The theoretically calculated activation energy barriers $E_a$ for hydrogen diffusion are relatively low (less than 0.1 eV), further supporting that such hopping can readily occur. A larger barrier value of $E_a$ ~0.2 eV is directly estimated by $T_2$ NMR data, suggesting possible slower hydrogen dynamics with the pre-exponential factor $D_0$ of diffusion coefficient ~10$^{-11}$ m$^2/$s.

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Zhichao Zhu, Xin Li, Ziru Ma, Yuanhua Xia, Ruizhi Qiu, Baijiang Lv, Guanyun Yan, Jianrong Zeng, Long Yang, Jianbo Ma, Benqiong Liu, Guangai Sun. 2025-06-10. Hydrogen diffusion in ceria: solid state NMR, combined scattering and spectroscopic studies, and ab initio calculations. https://arxiv.org/abs/2506.08789

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