Magnetic Co@g-C3N4 Core–Shells on rGO Sheets for Momentum Transfer with Catalytic Activity toward Continuous-Flow Hydrogen Generation

Magnetic core–shell structures provide abundant opportunities for the construction of multifunctional composites. In this article, magnetic core–shells were fabricated with Co nanoparticles (NPs) as cores and g-C3N4 as shells. In the fabrication process, the Co@g-C3N4 core–shells were anchored onto the rGO nanosheets to form a Co@g-C3N4-rGO composite (CNG-I). For hydrogen generation from the hydrolysis of NaBH4 or NH3BH3, the Co NP cores act as catalytic active sites. The g-C3N4 shells protect Co NPs cores from aggregating or growing. The connection between Co NPs and rGO was strengthened by the g-C3N4 shells to prevent them from leaching or flowing away. The g-C3N4 shells also work as a cocatalyst for hydrogen generation. The magnetism of Co NPs and the shape of rGO nanosheets achieve effective momentum transfer in the external magnetic field. In the batch reactor, a higher catalytic activity was obtained for CNG-I in self-stirring mode than in magneton stirring mode. In the continuous-flow process, stable hydrogen generation was carried out with CNG-I being fixed and propelled by the external magnetic field. The separation film is unnecessary because of magnetic momentum transfer. This idea of the composite design and magnetic momentum transfer will be useful for the development of both hydrogen generation and multifunctional composite materials.