Preparation and optimization of highly active Co3O4 catalyst for hydrogen generation from NaBH4 hydrolysis

Abstract

The oxidation state and phase structure of oxide catalysts play a crucial role in NaBH₄ hydrolysis. In this study, diverse Co₃O₄ catalysts were synthesized via the EDTA-citric acid complexing method and employed for hydrogen production from NaBH₄ hydrolysis. The impacts of different calcination temperatures on crystalline structure, microstructure, and catalytic performance of Co₃O₄ catalysts were examined systematically. It was observed that the calcination temperature cannot affect the crystal structure of Co₃O₄ catalysts, but it significantly influences their crystallinity, induction period and catalytic performance. The bulk crystallization of Co₃O₄ remained unaltered after reduction by NaBH₄, while its surface layer would transform into an amorphous phase, forming a core-shell structure. Moreover, the ratio of Co²⁺/Co³⁺ on the surface of the Co₃O₄ catalyst is substantially enhanced and more oxygen defects can be obtained through an in-situ reduction. The experimental results demonstrated that all Co₃O₄ catalysts exhibit an induction period before attaining a higher hydrogen generation rate. And the intrinsic catalytic activity of Co₃O₄ catalysts initially increases and then declines with the ascending calcination temperature, whereas their cyclic stability monotonically increases with calcination temperature. The Co₃O₄ catalyst achieves its highest catalytic activity at 1000 °C and the maximum cyclic stability at 1100 °C.