Co and Co 3 O 4 in the Hydrolysis of Boron-Containing Hydrides: H 2 O Activation on the Metal and Oxide Active Centers.

This work focuses on the comparison of H 2 evolution in the hydrolysis of boron-containing hydrides (NaBH 4 , NH 3 BH 3 , and (CH 2 NH 2 BH 3 ) 2 ) over the Co metal catalyst and the Co 3 O 4 -based catalysts. The Co 3 O 4 catalysts were activated in the reaction medium, and a small amount of CuO was added to activate Co 3 O 4 under the action of weaker reducers (NH 3 BH 3 , (CH 2 NH 2 BH 3 ) 2 ). The high activity of Co 3 O 4 has been previously associated with its reduced states (nanosized CoB n ). The performed DFT modeling shows that activating water on the metal-like surface requires overcoming a higher energy barrier compared to hydride activation. The novelty of this study lies in its focus on understanding the impact of the remaining cobalt oxide phase. The XRD, TPR H 2 , TEM, Raman, and ATR FTIR confirm the formation of oxygen vacancies in the Co 3 O 4 structure in the reaction medium, which increases the amount of adsorbed water. The kinetic isotopic effect measurements in D 2 O, as well as DFT modeling, reveal differences in water activation between Co and Co 3 O 4 -based catalysts. It can be assumed that the oxide phase serves not only as a precursor and support for the reduced nanosized cobalt active component but also as a key catalyst component that improves water activation.