Synergistic Ruthenium Single-Atom and Nanoparticles in Nickel as Cooperative Catalysts for the Alkaline Hydrogen Evolution Reaction

Abstract

Efficient hydrogen evolution reaction (HER) catalysts that reduce the use of noble metals and can be synthesized on a large scale are essential for advancing Anion Exchange Membrane Water Electrolyzers (AEMWE) toward commercialization. Herein, we present a composite catalyst where Ru nanoparticles coexist with Ru single-atom alloys (SAA) dispersed within Ni nanoparticles (Ru-SAA/Ni) creating a highly active HER electrocatalyst. Using a one-pot and scalable synthesis method, we can adjust the material composition from SAA (with ≤0.4 at.% Ru) to composite structures. Comprehensive characterization using XPS, XAS, and TEM confirms Ru-SAA formation at low Ru content and composite structures at higher content. Electrochemical evaluations conducted in a three-electrode setup reveal that Ru-SAA/Ni composites achieve HER performances on par with Pt/C. Computational insights suggest that the water dissociation is significantly faster at the Ru/Ni interface compared to extended surfaces. These active sites are also thermodynamically at least as active, thus avoiding excessive accumulation of reaction intermediates (H*, OH*). All these results highlight the synergistic interaction between Ru SAAs and Ru nanoparticles and their potential for large-scale applications with minimal use of precious metals. Finally, the materials are processed and tested into AEMWE and allow reaching 1.85 V at 0.5 A cm-2 with a total noble metal loading of only 0.1 mg cm-2.