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

Abstract

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 N2 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 H2 with a H2 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 (~100 % H2 generation efficiency) over multiple hydrolysis cycles without significant changes of morphology and microstructure. The catalytic hydrolysis mechanism for H2 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 H2 generation from the hydrolysis of NaBH4.