Formation and Activity Enhancement of Surface Hydrides by the Metal–Oxide Interface

Abstract

The observation of hydride species in reduced ceria has triggered recent interest because the formation of hydrides in solid catalysts is limited although hydrides are widely explored in homogeneous catalysis as active species for hydrogenation reactions. Here, a strategy is proposed to enhance the formation and activity of surface hydrides on oxide‐based catalysts via the construction of metal–oxide interface. Specifically, during the reaction with H2, Cu supported on CeO2 nanorods (NRs) is found to enhance the formation of hydride species, with the capacity more than an order of magnitude higher than that of CeO2 NRs. Moreover, sub‐nanometer clusters (sub‐NCs) of Cu supported on CeO2 NRs can enhance the formation and activity of surface hydrides, much more superior to that of Cu nanoparticles on CeO2 NRs. A combination of ambient‐pressure photoelectron spectroscopy techniques has enabled in situ measurements of hydrogen interaction and as such to directly correlate the electronic structures of solid catalysts with their activity. A strong metal–support interaction between undersaturated Cu clusters with CeO2 is found to account for the enhanced stability and reactivity of surface hydrides at the (sub‐NCs) Cu–CeO2 interface, which provides insight for the design of highly efficient catalysts for catalytic hydrogenation reactions.

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

“…4b and c). The superior CO 2 methanation reaction on 5Ni/La 2 O 3 might be due to the enhanced H 2 adsorption at the metal-oxide interfaces, 31 We have shown that the oxygen vacancies formed at the metaloxide interface of Ni/La 2 O 3 enhance H 2 adsorption with a strong binding strength, which benefits CO 2 methanation. More importantly, we found the enhanced H 2 adsorption by interfacial oxygen vacancies is ubiquitous for the supported transition metal nanoparticles on La 2 O 3 , not limited to the above-mentioned Ni/La 2 O 3 .…”

“…It is worth noting that the hydrogen adsorption favors the formation of lanthanum oxyhydride species at the metal-oxide interfaces. Recently, it has been reported that the surface oxyhydride species could be formed on the reducible CeO 2 during hydrogen adsorption at elevated pressures, [31][32][33][34][35] which brings about a significant effect on the catalytic performance of CeO 2 -supported metal catalysts. 30,36 Here, we also demonstrated that on pure La 2 O 3 surfaces, lanthanum oxyhydride could not be formed due to the non-reducible nature of La 2 O 3 .…”

Polyhedral Organic Silsesquioxane Cage Structures Formed via Reaction of Methylchlorosilanes with Re/CeO2 in Catalytic Oxygen Depletion–Regeneration Cycle

“…The silicon–hydride reaction is analogous to the heterolytic cleavage of H 2 on ceria and the formation of surface and bulk hydride species, which are promoted by supported transition-metal catalysts (e.g., Cu, Pd, etc.) and facilitated by the oxygen vacancies of the reduced ceria. − Since no H n -T n cage structures are detected, it is apparent that the H–O exchange reaction is able to outcompete the formation of any cage structures with Si–H vertices.…”

Selective Hydrogenation of Propyne to Propene Promoted by Synergistic Effect of Surface Oxygen Vacancies and Hydride Species on Ceria

“…11 Furthermore, Li et al revealed a novel homolytic dissociation process of H 2 to two Ce−H hydride species (2Ce Ov 3+ + H 2 → 2Ce Ov 4+ −H − ) at two Ce 3+ −O v sites on prereduced CeO 2−x powder and thin film, 10 which is kinetically favorable at relative low temperature and leads to the oxidation of Ce 3+ to Ce 4+ as well as the formation of hydrides at oxygen vacancies. 7,12,13 For selective alkyne hydrogenation reactions, it was previously proposed that the immobile surface oxygen atoms on the CeO 2 surface were the active centers, 5,14 where H 2 molecule homolytically dissociates to two reactive OH groups and participates in the dissociative adsorption of alkyne molecule for subsequent hydrogenation, 4,6 whereas O v sites were suggested to be detrimental to both the activity and selectivity of the reaction. However, with the revealing of the important role of oxygen vacancies within ceria for the complex H 2 -ceria interaction, ceria-based catalysts with a proper concentration of O v have also been reported to be beneficial to the reaction.…”