MOF-Templated Hierarchical Porous Hollow Core-Shell Framework Cobalt Oxide for Enhancing Hydrogen Generation from Borohydride-Based Hydrolysis

Designing and fabricating a competent cobalt-based catalyst for sodium borohydride (NaBH4) hydrolysis is of great importance. The present work reports the synthesis of hierarchical porous hollow core-shell framework cobalt oxide (HCSCO) via etching and calcination processes, which is then employed for catalyzing NaBH4 hydrolysis. The surface morphology and the hollow core-shell framework of HCSCO were revealed by scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses; the crystalline structure and the formation of Co3O4 in HCSCO were determined by X-ray diffraction (XRD) and Raman spectroscopy; the surface area and porosity of HCSCO were verified by N-2 adsorption-desorption isotherm; and X-ray photoelectron spectroscopy (XPS) was utilized to examine the chemical states of HCSCO. The as-prepared HCSCO showed prominent catalytic hydrolysis of NaBH4 to generate H-2 with a H-2 generation rate of 441 ml min(-1) gcatalyst(-1) and a low activation energy (Ea) of 34.8 kJ mol(-1). This Ea value of HCSCO is substantially lower than that of other catalysts, including noble metal catalysts or composites reported in the literature. Besides, HCSCO could remain its superb activity (similar to 100 % H-2 generation efficiency) over multiple hydrolysis cycles without significant changes of morphology and microstructure. The catalytic hydrolysis mechanism for H-2 generation from NaBH4 using HCSCO is also proposed. This work provides a valuable strategy for the synthesis and fabrication of state-of-art catalysts for H-2 generation from the hydrolysis of NaBH4.