# Synthesis of Elastic Metallic Nickel by Solvent‐Ligand‐Mediated Reductive Assembly

## TL;DR

Scientists developed a flexible metallic nickel foam using a solvent and ligand method, which could be useful for lightweight and durable materials.

## Contribution

A new method for synthesizing elastic metallic nickel using solvent-ligand-mediated reduction is introduced, enhancing flexibility and scalability.

## Key findings

- Diethanolamine solvent reduces Ni2+ ions and assembles them into 3D metallic nickel sponges.
- Acetic acid-assisted solvent optimization improves reaction kinetics and coordination density on nickel surfaces.
- The synthesized nickel sponges show efficient electrocatalytic activity for hydrogen and oxygen evolution reactions.

## Abstract

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.

The novel elastic metallic nickel, featuring ligands coordinating on the metal surface, is synthesized via rational selection of reduction and structure‐directing organic solvents. Moreover, by modulating solvent composition and incorporating acetic acid ligands, sufficient ligands are enabled to coordinate with the metal surface, thereby improving the mechanical flexibility of metallic nickel, and enabling the fabrication of large‐scale elastic metallic nickel.