A research team led by Prof. LIANG Changhao from the the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has developed a novel method for synthesizing carbon nanotube (CNT)-supported intermetallic RuM (M = Cu, Rh, and Pd) alloys dominated by sub-5 nm nanoparticles (NPs). 

Their findings were published in Advanced Science.

Sub-5 nm Ru-based alloys have gained attention as promising electrochemical catalysts for water splitting. However, their synthesis has been constrained by thermodynamic immiscibility, which limits the development of a universally applicable preparation method. 

In this study, the research team employed nanosecond laser ultrafast confined alloying (LUCA) to overcome the immiscible-to-miscible transition barrier in the synthesis of CNT-supported sub-5 nm bimetallic RuM alloy NPs.

Among the synthesized catalysts, Ru95Cu5/CNTs demonstrated outstanding electrocatalytic performance in alkaline hydrogen evolution reaction (HER), achieving an overpotential of just 17 mV and a Tafel slope of 28.4 mV dec⁻¹ at 10 mA cm⁻². 

Additionally, the catalyst exhibited remarkable stability, maintaining its performance over 5,000 cyclic voltammetry cycles. The Ru₉₅Cu₅/CNTs catalyst significantly outperformed LUCA-synthesized Ru₈₆Rh₁₄/CNTs, Ru₈₉Pd₁₁/CNTs, Ru, and Cu NP catalysts, as well as commercial benchmark 20% Pt/C catalysts. 

Moreover, it exceeded the performance of other mainstream Ru-based catalysts, including wet chemistry-synthesized RuRh particles (overpotential of 25 mV, Tafel slope of 47.5 mV dec⁻¹) and RuCu/CNTs synthesized via flash Joule heating (overpotential of 39 mV).

The alloying of non-noble metal Cu with varying atomic ratios of RuCu alloys is appealing owing to the low price of Cu and cost-effective synthesis for large-scale practical applications. 

This study highlights the great potential of LUCA for screening new classes of HER catalysts.

RuM/CNTs (M = Cu, Rh, and Pd) composites size/composition (Image by YE Yixing)