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 V_o–Co–Sn_5:x) were synthesized via a simple co-precipitation–calcination method under mild reaction conditions. The catalyst containing an optimized Co/Sn atomic ratio of 5:2 (V_o–Co–Sn_5:2) exhibited robust catalytic performance with a turnover frequency value of 17.6 \(\text{mol}_{{\text{H}}_{2}}\)·mol_metal⁻¹·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.