Immiscible Ruthenium-Cadmium Alloy for Acidic Oxygen Evolution Reaction

As a common catalyst for the oxygen evolution reaction in acids, metallic ruthenium (Ru) suffers from sluggish kinetics and low stability. Although cadmium (Cd) could improve the activity of the Ru catalyst through an alloying effect, Ru and Cd are thermodynamically immiscible, and it is hard to produce a RuCd alloy via conventional chemical synthesis. In this work, we overcome the thermodynamical limit and synthesize RuCd alloy nanoparticles by the technique of pulsed-laser ablation in liquid (PLAL). The prepared RuCd nanoparticles show an OER overpotential as low as 155 mV@10 mA cm^-2 in 0.5 M H₂SO₄, much better than the commercial RuO₂ catalyst (305 mV). Theoretical calculations and in situ spectroscopy indicate that the incorporation of Cd effectively reduces the energy barrier of the OER and stabilizes the RuCd catalyst, thus significantly improving the catalytic activity and durability. When used as an anode catalyst for a PEM water electrolyzer, the RuCd alloy nanoparticles show a long-term durability over 50 h at a water-splitting current density of 50 mA cm^-2, implying great potential for practical applications.