Hierarchically porous CoP@CNR nanorod derived from metal-organic frameworks as noble-metal-free catalyst for dehydrogenization of ammonia-borane

Abstract

The development of effective and inexpensive catalysts for hydrogen release from hydrogen-storage compounds such as ammonia-borane (AB) is crucial in academic and industrial fields for the reduction of greenhouse gas emissions. Herein, we report a facile method to fabricate well-dispersed CoP nanoparticles (NPs) with an average particle size of 4.3 nm. The CoP NPs were encapsulated in carbonaceous nanorods (CoP@CNR) using metal-organic frameworks (MOFs) as a sacrificial precursor. The CoP@CNR catalysts were characterized, and their catalytic performance for the dehydrogenization of AB at 25 °C in an alkaline solution was determined. CoP@CNR (400) with a hierarchically meso-microporous structure (micropore area = 73.6 m2 g-1 and micropore volume = 0.19 cm3 g-1) and a specific surface area of 88.4 m2 g-1 was synthesized during the phosphorization process. The hierarchically porous structure was instrumental in immobilizing metal NPs and accelerating mass diffusion. Moreover, the incorporation of P into Co NPs modified the electronic structure of the latter and accelerated the dehydrogenization of AB. This resulted in a hydrogen release rate of 10,014 mL/(min·g), which was 13 times higher than that of the pure Co nanocatalyst. In addition, we reported the kinetic studies for AB hydrolysis catalyzed by CoP@CNR (400) in terms of the temperature effect, isotope effect, catalyst concentration, AB concentration, and NaOH concentration.