Sub-4 nm Ru-RuO<sub>2</sub> Schottky Nanojunction as a Catalyst for Durable Acidic Water Oxidation
Yuxiang Song, Wanghui Zhao, Zhi Wang, Weili Shi, Feiyang Zhang, Zhuoming Wei, Xin Cui, Yihan Zhu, Tao Wang, Licheng Sun, Biaobiao Zhang
Abstract
RuO 2 with high intrinsic activity for water oxidation is a promising alternative to IrO 2 in proton exchange membrane (PEM) electrolyzer, but it suffers from long-term stability issues due to overoxidation. Here, we report a sub-4 nm Ru-RuO 2 Schottky nanojunction (Ru-RuO 2 –SN) prepared by a microwave reaction that exhibits high activity and long-term stability in both three-electrode systems and PEM devices. The lattice strain and charge transfer induced by the metal-oxide SN increase the work function of the Ru-RuO 2 –SN, optimize the local electronic structure, and reduce the desorption energy of the metal site to the oxygen-containing intermediates; as a result, it leads to the oxide path mechanism (OPM) and inhibits the excessive oxidation of surface ruthenium. The Ru-RuO 2 –SN requires only 165 mV overpotential to obtain 10 mA·cm –2 with 1400 h stability without obvious activity degradation, achieving a stability number (6.7 × 10 6 ) matching iridium-based catalysts. In a PEM electrolyzer with Ru-RuO 2 –SN as an anode catalyst, only 1.6 V is needed to reach 1.0 A·cm –2 and it shows long-term stability at 100 mA·cm –2 for 1100 h and at 500 mA·cm –2 for 100 h. The reaction mechanism for the high stability of Ru-RuO 2 –SN was analyzed by density functional theory calculations. This work reports a durable, pure Ru-based water-oxidation catalyst and provides a new perspective for the development of efficient Ru-based catalysts.