A unique sandwich-structured Ru-TiO/TiO2@NC as an efficient bi-functional catalyst for hydrogen oxidation and hydrogen evolution reactions

Developing active and stable non-Pt electrocatalysts for hydrogen oxidation (HOR) and evolution reactions (HER) are critical for anion exchange membrane fuel cells and water electrolyzers. Herein, we report a highly active and robust electrocatalyst Ru-TiO/TiO2@NC, in which Ru nanoclusters are sandwiched between TiO/TiO2 nanosheets and nitrogen-doped carbon layers. Taking advantage of both the optimized Ru-TiO/TiO2 interaction and the conductive carbon coating layers, the Ru-TiO/TiO2@NC exhibits both exceptional HOR/HER activity and superior stability, outperforming Pt/C in the alkaline solution. The HOR mass activity reaches up to 107.2 A gRu-1 at an overpotential of 50 mV, and the specific exchange current density is 0.271 mA cm-2. The HER over-potential at 10 mA cm-2 is only 39 mV, 34 mV lower than required by Pt/C. More importantly, the Ru-based catalyst exhibits excellent anti-oxidation ability by virtue of the unique sandwich structure. Density functional theory calculations discover that the d-band center of Ru in Ru-TiO/TiO2 is downshifted by 0.29 eV compared to Ru-TiO2, decoupling and optimizing the Had/OHad adsorption on Ru, i.e., Had is promoted, while OHad is inhibited and transferred to TiO/TiO2. As a result, (i) the energy required by the potential determining step of HOR/HER is lowered, and (ii) the anti-oxidation ability of the Ru-TiO/TiO2 is enhanced. This work not only addresses the issue of Ru passivation at high anode potentials but also provides an innovative and versatile approach to designing advanced electrocatalysts.

Automated summary

In this study, a highly active and stable electrocatalyst Ru-TiO/TiO2@NC is developed for hydrogen oxidation and evolution reactions. The catalyst exhibits exceptional activity and stability, outperforming the traditional Pt/C catalyst. The unique sandwich structure and optimized interaction between Ru and TiO/TiO2 contribute to the enhanced performance of this Ru-based catalyst.