Confining Flat Ru Islands into TiO 2 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 _ad ) inhibits the supply of the adsorbed hydrogen (Had). Herein, the coexisting RuOTi 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 sites in RuOTi bonds with more positive charge and stabilize Ru atoms of RuTi bonds with the low-valence. The strength of Ru-OH _ad is then weakened by the oxophilicity of positively charged Ti atom in Ru-O-Ti bonds and the stronger Ti-OH _ad bond could release active Ru sites, especially for low-valence Ru in RuTi bonds, to serve as exclusive Had sites. As expected, F-Ru@TiO ₂ shows a low HER overpotential of 74 mV at 1000 mA cm ^-2 and an ultrahigh mass activity 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.
(© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)