Microwave-intensified hydrolysis for high efficiency hydrogen generation over magnetically separable Co₃O₄-carbon nanotube composites

Microwave (MW)-assisted process intensification technology has the potential to improve catalytic conversion under mild reaction conditions. In this study, a series of MW-sensitive CNTs-Co₃O₄ composites were designed and synthesized as catalysts for the conversion of NaBH₄ to H₂. It was found that MW irradiation leads to a 19.6 (35 °C) to 49.5% (55 °C) increase in the hydrogen generation rate (HGR) of NaBH₄ hydrolysis catalyzed by the CC14, which is attributed to the combined contribution of thermal and non-thermal effects of microwave irradiation. Moreover, the NaBH₄ hydrolysis catalyzed by CC14 catalyst at different heating modes followed the zero-order kinetic model, and the pre-exponential factor of NaBH₄ hydrolysis catalyzed by CC14 catalyst under MW irradiation was approximately 157 times higher than under conventional heating, indicating that microwave irradiation increased the effective collision frequency at the reaction interface of CC14 catalyst. In addition, the selective and instantaneous heating of microwave irradiation was demonstrated by using a specially designed pseudo-homogeneous low temperature reaction system. Moreover, DFT calculations show that the rate-determining step of NaBH₄ hydrolysis is H₂O dissociation.