Laser Ultrafast Confined Alloying of Sub-5 nm RuM (M = Cu, Rh, and Pd) Particles on Carbon Nanotubes for Hydrogen Evolution Reaction

Abstract

Thermodynamic immiscibility is a challenge for intermetallic alloying of sub-5 nm Ru-based alloys, which are excellent electrochemical catalysts for water splitting. In this study, nanosecond laser ultrafast confined alloying (LUCA) is proposed to break the immiscible-to-miscible transition limit in the synthesis of carbon nanotubes (CNTs) supported sub-5 nm bimetallic RuM (M = Cu, Rh, and Pd) alloy nanoparticles (NPs). 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. Benefiting from the synergistic alloying effect and resultant H/OH binding energy alteration, the Ru₉₅Cu₅/CNTs catalysts display excellent electrocatalytic alkaline hydrogen evolution reaction (HER) activity with an overpotential of 17 mV and Tafel slope of 28.4 mV dec⁻¹ at 10 mA cm⁻², and high robustness over long-term 5000 cyclic voltammetry cycles. The performance is much better than LUCA-synthesized CNTs-supported Ru₈₆Rh₁₄, Ru₈₉Pd₁₁, Ru, and Cu NPs catalysts, commercial benchmark 20% Pt/C, and other mainstream Ru-based catalysts including wet chemistry-synthesized RuRh particles (overpotential of 25 mV, Tafel slope of 47.5 mVdec⁻¹) and RuCu/CNTs (overpotential of 39 mV) synthesized using the flash Joule heating method, indicating the great potential of LUCA for screening new classes of HER catalysts.