Component-Controlled Synthesis of Necklace-Like Hollow Ni_XRu_y Nanoalloys as Electrocatalysts for Hydrogen Evolution Reaction

Developing highly efficient and long-durable nanoalloy electrocatalysts toward the hydrogen evolution reaction (HER) are highly desirable for implementation of the water-splitting technique to prepare clean fuels. Though great progress has been achieved, controllable synthesis of hollow Ni_xRu_y nanoalloys with a wide component ratio range remains a challenge and their applications for HER have not been explored. Here, a series of necklace-like hollow Ni_xRu_y nanoalloys (Ni₇₂Ru₂₈, Ni₆₃Ru₃₇, Ni₄₃Ru₅₇, and Ni₂₉Ru₇₁) are prepared using the galvanic replacement reaction between the Ni nanochains and RuCl₃·3H₂O and the hollowing process based on the Kirkendall effect. Electrochemical tests reveal that those Ni_xRu_y nanoalloys can efficiently catalyze HER in acidic media. Among them, the Ni₄₃Ru₅₇ nanoalloy exhibits the highest catalytic activity with an overpotential of 41 mV to attain a current density of -10 mA cm^-2, outperforming other Ni_xRu_y nanoalloys and close to commercial Pt/C. Additionally, its current density will exceed Pt/C catalyst as the overpotential surpasses 102 mV. Moreover, such Ni₄₃Ru₅₇ nanoalloy also shows an exceptional durability that can continuously work for 8 h only with a little loss of activity. Deduced from some featured spectroscopic and electrochemical analysis, the excellent catalytic performance of Ni₄₃Ru₅₇ nanoalloy is attributed to the proper component ratio and effective electronic coupling of Ni and Ru, causing the faster interfacial electron transfer kinetics and more available active sites on it compared with other Ni_xRu_y nanoalloy ones.