Engineering of unique Ni-Ru nano-twins for highly active and robust bifunctional hydrogen oxidation and hydrogen evolution electrocatalysis.

[Display omitted] • A unique Ni/Ru hetero-nano-twin catalyst with rich interfaces. • Electron re-distribution at interfaces of Ni/Ru twins balances H ad /OH ad adsorption. • Ni 1 Ru 1 twin shows superior activity for alkaline HOR/HER as compared to Pt/C. • Ni 1 Ru 1 twin is remarkably stable with a break-down potential up to 0.25 V RHE. • The crucial role of the intimate Ni/Ru nano-twin is demonstrated and discussed. Herein, unique Ni-Ru nano-twins (Ni 1 Ru 1 /C) are reported for the first time as a superior bifunctional catalyst for hydrogen oxidation/hydrogen evolution reaction (HOR/HER). Compared to Pt/C, the Ni 1 Ru 1 /C nano-twins display a remarkable HOR activity with a comparable mass activity of 0.12Amg−1 metal and superior HER activity, with an overpotential (դ) of only 16 mV for achieving a cathodic HER current of 10mAcm−2, together with a high turnover-frequency of 1.88 s−1 (@դ=30 mV). Additionally, the HOR limiting current of the Ni 1 Ru 1 /C nano-twins can be maintained up to a break-down potential of 0.25V RHE , demonstrating excellent electrochemical stability. Experimental and theoretical studies reveal that the electron re-distribution at the Ni/Ru interface of Ni-Ru nano-twins optimizes the binding energy of the adsorbed hydrogen (H ad) and the adsorbed hydroxyl (OH ad) intermediates, allowing the HOR/HER to proceed via a low energy barrier. This work provides a strategy to synthesize hetero-metal nano-twins as promising multi-functional catalysts and highlights the critical role of interfaces for heterostructured electrocatalysts. [ABSTRACT FROM AUTHOR]