Amorphization of Metal Nanoparticles by 2D Twisted Polymer for Super Hydrogen Evolution Reaction

Hydrogen generation by electrolysis of water in an alkaline solution is a promising technology for clean hydrogen energy. Amorphous materials show much better performance than their crystalline counterparts. However, it is still challenging to design amorphous metal materials. Here, a series of amorphous transition metal nanoparticles (NPs) is successfully synthesized using a twisted covalent organic network (CON) that can provide twisted carbon layers as well as asymmetrically distributed nitrogen. With the fixed monomer pore, a low loading amount of RuCl3 results in amorphous-only Ru nanoclusters (NCs, 1.5 nm), while a high content of RuCl3 leads to crystalline dominant Ru NPs (3 nm). The mixed phased Ru-CON catalyst for the hydrogen evolution reaction (HER) shows extremely low overpotential at 10 mA cm(-2) (12.8 mV in 1.0 m KOH) and superior stability (after 100 h test, current loss 5.3% at 75 mA cm(-2)). More importantly, amorphous-only Ru-CON with smaller Ru NCs shows much better mass activity and considerable stability compared to mixed-phase Ru-CON materials since amorphous Ru NPs can provide more active sites than in their crystalline state. With this strategy, amorphous Fe NPs and Ir NPs are successfully prepared for extended applications, and the HER activities are reported.