Ni@RuM (M=Ni or Co) core@shell nanocrystals with high mass activity for overall water-splitting catalysis

Developing efficient water-splitting electro-catalysts with high mass activity is in urgent need for large-scale sustainable production of hydrogen but, still remains as a big challenge. Herein, we report a one-pot method to fabricate a series of core@shell Ni@RuM (M=Ni or Co) nanocrystals (NCs) with Ni as the core and tunable RuM (M=Ni or Co) as the alloy shell for efficient water-splitting catalysis. Among these core@shell NCs, the obtained Ni@RuNi NCs exhibit the highest intrinsic activity for hydrogen evolution reaction (HER) and possess an outstanding mass activity of 1590 mA mg(Ru)(-1) at 0.07 V vs. reversible hydrogen electrode (RHE), which is 1.7 times higher than that of commercial Pt/C (950 mA mg(Pt)(-1)). As for oxygen evolution reaction (OER), the prepared Ni@Ru0.4Co0.6 NCs with optimized shell composition achieve more enhanced mass activity of 270 mA mg(Ru)(-1) at 1.56 V vs. RHE, approaching three times higher than that of commercial RuO2 (89 mA mg(Ru)(-1)). The superb mass activity of these Ni@RuM (M=Ni or Co) NCs can be attributed to their core@shell structure and modulated electronic structure through alloying with Ni or Co metal in the shell.