Maximizing Metal-Support Interactions in Pt/Co3O4 Nanocages to Simultaneously Boost Hydrogen Production Activity and Durability.

Abstract

Catalytic hydrolysis of ammonia borane (AB) provides an effective way to generate pure H2 at ambient temperature for fuel cells. Pt-based catalysts usually exhibit great initial activity toward this reaction but deactivate quickly. Here, we report that the metal-support interactions in Pt/Co3O4 nanocages can simultaneously accelerate the H2 generation and enhance the catalyst's stability. The Pt/Co3O4 catalyst is made for the first time by embedding Pt clusters (∼1.2 nm) in a high-surface-area Co3O4 nanocage to maximize the metal-support interface. The turnover frequency of the Pt/Co3O4 catalyst is about nine times higher than that of commercial Pt/C and outperforms almost all other Pt-based catalysts. X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, in situ spectroscopy, and density functional theory calculations suggest that the Co3O4 nanocages with rich oxygen vacancies facilitate the adsorption and dissociation of H2O to give electropositive H (Hδ+), while the in situ embedded Pt clusters can accelerate the formation of electronegative H (Hδ-) from AB. Subsequently, the Hδ+ and Hδ- spill over to the abundant interfacial sites and bond into H2. In addition to this dual-function synergy effect, the strong metal-support electronic interactions between Co3O4 and Pt benefit the desorption of poisonous B-containing byproducts from Pt sites. This effect together with cluster anchoring leads to a fivefold enhancement in durability compared to commercial Pt/C. The metal-support interactions revealed in this study provide more options for catalyst design toward facile H2 production from chemical hydrogen storage materials.