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.