Modulation the electronic structure of hollow structured CuO-NiCo2O4 nanosphere for enhanced catalytic activity towards methanolysis of ammonia borane

Abstract

Rational construction of cost-efficient catalysts with high activity and durability for hydrogen production from ammonia borane (AB) methanolysis is highly desirable but remains a substantial challenge. In this work, we constructed a series of non-noble-metal based hollow CuO-NiCo2O4 nanospheres composite, in which the CuO-NiCo2O4-0.8 nanospheres exhibit robust catalytic activity with a high turnover frequency (TOF) of 23.2 molH2 molcat.−1 min−1 towards AB methanolysis. Systemic experimental and computational studies reveal the promotion of activity results from the synergistic effect between CuO and NiCo2O4. It is revealed the combination of CuO with NiCo2O4 caused the electrons migration among Cu, Ni and Co sites and the change of d-band centers of catalyst, thus enhancing the adsorption process of CH3OH and AB molecules on catalyst and subsequently promoting the catalytic activity. Moreover, the Co center in CuO-NiCo2O4 composite is recognized as active sites by DFT calculations. Mechanistically, the rate determining step is the dissociation of O–H bond in CH3OH, which is confirmed by kinetic isotopic effect experiment. A plausible mechanism of methanolytic dehydrogenation of AB on CuO-NiCo2O4 was proposed based on experiment and DFT calculations. These findings should shed light on the rational construction of cost-efficient catalysts with high performance for hydrogen production from AB methanolysis.