Optimization of valence and crystal structure of nickel-cobalt composites for efficient catalytic hydrolysis of borohydrides

Abstract

Borohydrides are promising for hydrogen storage applications owing to borohydride hydrolysis reactions (BHR) characterized by controlled hydrogen evolution. However, the understanding of electronic structure-activity relationships and macroscopic synthesis of transition metal-based catalysts remains challenging. Herein, we employed a high-gravity technique coupled with impregnation-phosphorization to prepare NiCo-P/O with homogeneous and small particle sizes. Experiments and characterizations reveal that the phosphorization procedure confers the material's ability to catalyze BHR by introducing low valence Ni and Co. The catalytic activity for BHR shows a strong dependence on the valence state. Besides, the particle size and crystal structure of the catalysts were optimized by modulating the high-gravity field, thus boosting the catalytic activity towards BHR. As a result, NiCo-P/O catalyzed BHR at 298 K could produce pure hydrogen at 2060 mL min−1 g−1. This work provides a valence-activity relationship insight and feasible macro-synthetic catalysis strategies for BHR.