Insights into the enhanced hydrogen adsorption on M/La 2 O 3 (M = Ni, Co, Fe).

Lanthanum oxide (La 2 O 3 ) possesses superior reactivity during catalytic hydrogenation, but the intrinsic activity of La 2 O 3 toward H 2 adsorption and activation remains unclear. In the present work, we fundamentally investigated hydrogen interaction with Ni-modified La 2 O 3 . Hydrogen temperature programmed desorption (H 2 -TPD) on Ni/La 2 O 3 shows enhanced hydrogen adsorption with a new hydrogen desorption peak at a higher temperature position compared to that on the metallic Ni surfaces. By systematically exploring the desorption experiments, the enhanced H 2 adsorption on Ni/La 2 O 3 is due to the oxygen vacancies formed at the metal-oxide interfaces. Hydrogen atoms transfer from Ni surfaces to the oxygen vacancies to form lanthanum oxyhydride species (H-La-O) at the metal-oxide interfaces. The adsorbed hydrogen at the metal-oxide interfaces of Ni/La 2 O 3 results in improved catalytic reactivity in CO 2 methanation. Furthermore, the enhanced hydrogen adsorption on the interfacial oxygen vacancies is ubiquitous for La 2 O 3 -supported Fe, Co, and Ni nanoparticles. Benefiting from the modification effect of the supported transition metal nanoparticles, the surface oxyhydride species can be formed on La 2 O 3 surfaces, which resembles the recently reported oxyhydride observed on the reducible CeO 2 surfaces with abundant surface oxygen vacancies. These findings strengthen our understanding of the surface chemistry of La 2 O 3 and shed new light on the design of highly efficient La 2 O 3 -based catalysts with metal-oxide interfaces.