Insights into the enhanced hydrogen adsorption on M/La2O3 (M = Ni, Co, Fe)

Abstract

Lanthanum oxide (La₂O₃) possesses superior reactivity during catalytic hydrogenation, but the intrinsic activity of La₂O₃ toward H₂ adsorption and activation remains unclear. In the present work, we fundamentally investigated hydrogen interaction with Ni-modified La₂O₃. Hydrogen temperature programmed desorption (H₂-TPD) on Ni/La₂O₃ 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 H₂ adsorption on Ni/La₂O₃ 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/La₂O₃ results in improved catalytic reactivity in CO₂ methanation. Furthermore, the enhanced hydrogen adsorption on the interfacial oxygen vacancies is ubiquitous for La₂O₃-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 La₂O₃ surfaces, which resembles the recently reported oxyhydride observed on the reducible CeO₂ surfaces with abundant surface oxygen vacancies. These findings strengthen our understanding of the surface chemistry of La₂O₃ and shed new light on the design of highly efficient La₂O₃-based catalysts with metal–oxide interfaces.