Exceptional activity of hollow porphyrin frameworks-confined Ni nanoparticles for hydrogen production from NaBH4 methanolysis

Abstract

Hollow framework materials have recently attracted broad interest owing to the multifarious superiorities, such as large surface area, adjustable pore structure, short transport distance, as well as high permeability. Herein, a nitrogen-rich hollow porphyrin framework (H-POF) was synthesized via SiO2 as hard template. Then, ultrafine Ni nanoparticles (NPs) were confined on the surface of H-POF via ultrasonic impregnation reduction method. The resultant Ni/H-POF catalyst shows an extraordinary catalytic performance toward the methanolysis of NaBH4, providing a hydrogen generation rate (HGR) value of 34720 mL·min−1·gmetal−1, which surpasses all heterogeneous catalysts ever reported with NaOH. Further experimental investigation confirms that the high catalytic activity can attributed to the large specific surface area and hollow structure of the support, small size of metal NPs, as well as the electron-donating effect of nitrogen atoms on metal NPs. Based on isotopic experiments, the breaking of OH bond in CH3OH is proved to be the rate-determining step (RDS) of NaBH4 methanolysis. This work provides valuable insights for rationally designing nitrogen-rich hollow framework materials for supporting ultrafine metal NPs, which will be used for the future energy-related applications.