Heterostructured Co3O4-SnO2 composites containing oxygen vacancy with high activity and recyclability toward NH3BH3 dehydrogenation

Ammonia borane (NH3BH3, AB) has been regarded as a promising chemical hydrogen storage material owing to its high hydrogen density and superior stability. Thus, the development of low-cost and high-efficient heterogeneous catalysts for the dehydrogenation of AB has attracted considerable scholarly attention. In this study, heterostructured Co3O4-SnO2 catalysts containing oxygen vacancy (V-o) with different Co/Sn atomic ratios (designated as Vo-C-o-Sn-5:x) were synthesized via a simple coprecipitation-calcination method under mild reaction conditions. The catalyst containing an optimized Co/Sn atomic ratio of 5:2 (V-o-C-o-Sn-5:2) exhibited robust catalytic performance with a turnover frequency value of 17.6 mol(H2)center dot mol(metal)(-1)center dot min(-1). Moreover, 82.6% of the original activity of the catalyst was retained after 14 catalytic cycles, indicating the high stability of the catalyst. Diversified characterization combined with the density functional theory (DFT) calculation confirmed the transfer of electrons from Co3O4 to SnO2 and the distribution of the separated charges on SnO2-Co3O4 interface. The transfer of electrons and the distribution of charges facilitated the adsorption and activation of water on the catalyst, thus accelerating the dissociation of H2O molecule (the rate-determining step of AB hydrolysis). It was found that the V-o adjusted the electron structure of the catalysts rather than acted as active sites. These findings will provide researchers with useful information for designing cheap and highly efficient catalysts for catalytic AB hydrolysis.

Automated summary

In this study, Co3O4-SnO2 catalysts containing oxygen vacancy (V-o) with different Co/Sn atomic ratios were synthesized and showed high catalytic performance and stability for the dehydrogenation of ammonia borane (AB). Diversified characterization and DFT calculation confirmed the electron transfer and charge distribution on the SnO2-Co3O4 interface, which enhanced water adsorption and activation, accelerating the rate-determining step of AB hydrolysis. The oxygen vacancy adjusted the electron structure of the catalysts rather than acted as active sites.