▎ 摘　　要

A novel one-step strategy is proposed to fabricate three-dimensional (3D) graphene hydrogel (GH) by simultaneous self-assembly and reduction of graphene oxide (GO) at 90 degrees C under atmospheric pressure, using L-cysteine (L-Cys) as both templating and reducing agent. The preparation process can be completed within 3 h without producing any contamination, which is a fast, facile, economical and green method for the fabrication of GH. The freeze-dried product - graphene aerogel (GA) - has high mechanical strength and thermal stability, with hierarchical pore structure and large specific surface area. More importantly, the as-prepared GA exhibits outstanding adsorption capacity towards organic dyes, which could be a potential candidate for efficient adsorbents in water purification. In addition, the established method is successfully extended to the preparation of platinum nanoparticle (PtNP)-loaded 3D graphene materials via one-step simultaneous reduction and assembly of metal ions and GO. The as-obtained PtNPs/GA with free-standing structure can act as a heterogeneous catalyst for the chemical reduction of p-nitroaniline, which shows excellent catalytic activity. The developed method is promising for preparing other graphene-based multifunctional composite materials.