Interface engineering of snow-like Ru/RuO nanosheets for boosting hydrogen electrocatalysis.

Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) due to its similar binding energy towards *H but lower price compared to Pt. Nevertheless, the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and unsatisfactory stability. Herein, we have fabricated and engineered two-dimensional (2D) Ru-based snow-like nanosheets with Ru/RuO interface (Ru/RuO SNSs) via a post-annealing treatment. Detailed characterizations and theoretical calculations indicate that the interfacial synergy, which is dependent on the temperature for annealing, can alter the hydrogen binding energy (HBE) and hydroxide binding energy (OHBE), as a result of the enhanced HOR and HER performance. Impressively, the optimal Ru/RuO SNSs display a mass activity of 9.13 A mg at an overpotential of 50 mV in 0.1 mol L KOH for HOR, which is 65, 304, and 21 times higher than those of Ru SNSs (0.14 A mg), RuO SNSs (0.03 A mg), and commercial Pt/C (0.43 A mg), respectively. Moreover, Ru/RuO SNSs display improved HER activity with a low overpotential of 20.2 mV for achieving 10 mA cm in 1 mol L KOH. This work not only provides an efficient catalyst for HOR and HER, but also promotes fundamental research on the fabrication and modification of catalysts in heterogeneous catalysis.