Activating transition metal via synergistic anomalous phase and doping engineering towards enhanced dehydrogenation of ammonia borane

Abstract

Seeking high-performing non-noble transition metal catalysts for hydrogen evolution from chemical hydrogen storage media is significant. Herein we demonstrate for the first time that anomalous crystal phase engineering coupled with heteroatom doping can remarkably activate transition metal (Ni as a proof-of-concept study) for boosting ammonia borane (AB) dehydrogenation. Ni nanoparticles with designated phase (fcc or hcp phase) encapsulated in carbon (fcc-Ni/C and hcp-Ni/C) can be readily derived from Ni-based MOF. Intriguingly, hcp-Ni/C featuring unconventional hcp phase can remarkably outperform fcc-Ni/C with common fcc phase in AB dehydrogenation. Moreover, by doping Cu, dramatically promoted catalysis can be further achieved for hcp-CuNi/C. From experimental and theoretical results, delicate crystal phase together with heteroatom doping engineering can optimize electronic structure of hcp-CuNi/C, facilitating rate-determining step (H2O dissociation), thereby boosting AB hydrolysis. This study details the first insight into the phase and doping engineering over non-noble transition metals for promoting AB dehydrogenation.