Abstract
Effective hydrogen evolution reaction (HER) under high current density and enhanced hydrogen oxidation reaction (HOR) over a wide potential range remain challenges for Ru-based electrocatalysts because its strong affinity to the adsorbed hydroxyl (OH(ad)) inhibits the supply of the adsorbed hydrogen (H(ad)). Herein, the coexisting Ru─O─Ti and Ru─Ti bonds are constructed by taking TiO(2) crystal confined flat-Ru clusters (F-Ru@TiO(2)) to cope with above-mentioned obstacles. The different electronegativity (χ(Ti) = 1.54 < χ(Ru) = 2.20< χ(O) = 3.44) can endow Ti in Ru─O─Ti bonds with more positive charge and stabilize Ru of Ru-Ti bonds with the low-valence. The strength of Ru─OH(ad) is then weakened by the oxophilicity of positively charged Ti in Ru─O─Ti bonds and the stronger Ti─OH(ad) bond could release active Ru, especially for low-valence Ru in Ru─Ti bonds, to serve as exclusive H(ad) sites. As expected, F─TiRu@TiO(2) shows a low HER overpotential of 74 mV at 1000 mA cm(-2) and an ultrahigh mass activity (j(0,m)) of 3155 A g(Ru) (-1) for HOR. More importantly, F─Ru@TiO(2) can tolerate the HER current density of 1000 mA cm(-2) for 100 h and the high anodic potential for HOR up to 0.5 V versus RHE.