▎ 摘　　要

We developed a general platform for the fabrication of transition metal oxide nanoparticles supported by a graphene foam (GI) by first coating it with a methacrylated gelatin (GelMA) hydrogel, which served as a 3D matrix for nanoparticle dispersion. The engineered GelMA/GF matrix was hydrophilic with good mechanical strength and high conductivity, therefore providing a good platform for the dispersion of a variety of metal/oxide precursors. Due to this platform, well-dispersed Co3O4 nanoparticles with the smallest size of 3 nm assembled on the nitrogen-doped graphene foam (Co3O4/NGF). The crystalline transformation from a CoCl2[H2O](2) precursor to Co3O4 was revealed by in operando X-ray diffraction and absorption techniques. After applying Co3O4/NGF as a free-standing electrocatalyst for water splitting, the nano-particles of size 3 nm exhibited optimal catalytic activity in alkaline media; the corresponding cell could promote water splitting at a current density of 10 mA cm(-2) with only 1.63 V and exhibited excellent stability in a 25 h long-term operation. Our results demonstrate that the GelMA hydrogel-coated 3D graphene foam can be a promising platform for the design and fabrication of graphene-based multifunctional materials.