Synthesis of Elastic Metallic Nickel by Solvent-Ligand-Mediated Reductive Assembly

Metallic foams hold significant promise as lightweight structural materials. However, most conventional metallic foams are inherently rigid and brittle, frequently undergoing structural collapse. There is an urgent demand to develop cost-effective, facile-to-synthesize metallic foams with enhanced flexibility. Herein, it is discovered that diethanolamine solvent, a multifunctional organic solvent, not only reduces Ni²⁺ ions but also induces the assembly of generated Ni⁰ units into 3D metallic nickel (Ni-BPHs) sponges. In addition, the optimization of the binary solvent ratio combined with an acetic acid-assisted method is demonstrated to markedly accelerate the reaction kinetics, concomitant with significantly enhance the coordination density of organic ligands on metallic nickel surface. This approach enables the synthesis of metallic nickel (Ni-BNSs) sponges with enhanced flexibility. The Ni-BPHs and Ni-BNSs as electrocatalysts that exhibit efficient activity and stability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. The solvent-ligand-mediated reduction and induced assembly strategy has also been demonstrated by extending to other similar ligands. This work marks an important advance in metallic nickel foams and provides a promising strategy for synthesizing mechanically flexible metallic sponges.