Confining Flat Ru Islands into TiO Lattice with the Coexisting Ru-O-Ti and Ru-Ti Bonds for Ultra-Stable Hydrogen Evolution at Amperometric Current Density and Hydrogen Oxidation at High Potential.

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) inhibits the supply of the adsorbed hydrogen (H). Herein, the coexisting Ru─O─Ti and Ru─Ti bonds are constructed by taking TiO crystal confined flat-Ru clusters (F-Ru@TiO) to cope with above-mentioned obstacles. The different electronegativity (χ = 1.54 < χ = 2.20< χ = 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 is then weakened by the oxophilicity of positively charged Ti in Ru─O─Ti bonds and the stronger Ti─OH bond could release active Ru, especially for low-valence Ru in Ru─Ti bonds, to serve as exclusive H sites. As expected, F─TiRu@TiO shows a low HER overpotential of 74 mV at 1000 mA cm and an ultrahigh mass activity (j) of 3155 A g for HOR. More importantly, F─Ru@TiO can tolerate the HER current density of 1000 mA cm for 100 h and the high anodic potential for HOR up to 0.5 V versus RHE.