To date, platinum (Pt)-based compounds are considered to be one of the most effective hydrogen evolution reaction (HER) catalysts under acidic conditions because of the appropriate strength of the Pt-H bond, which facilitates hydrogen desorption from the surface of the catalyst. However, the scarcity and high cost of Pt greatly limits its use in industrial applications. Recently, non-precious metal-based catalysts have been studied extensively, such as carbides, nitrides, oxides, phosphides, sulfides, and selenides of transition metals. Unfortunately, these catalysts generally exhibit relatively higher overpotentials, Tafel slopes, and lower stabilities under large current densities in comparison to Pt/C. As for cheaper Ru metal, which shows similar metal-hydrogen bond strengths compared with that of Pt, only a few HER applications have been reported unfortunately. As is well-known, the support material plays an important role in optimizing the local geometric and electronic structures of single-metal sites because of strong metal–support interactions. In the development of support materials, the stabilizing effect and the tuning effect over the single catalytic sites should be considered. To date, supports that guarantee atomic dispersion of metal sites are largely limited to oxides and carbon-based materials. However, metallic oxides often exhibit poor electrical conductivity and resistance to acidic corrosion in electrocatalytic tests. Additionally, the carbon-based matrix also shows deficiencies in stability during the electrocatalytic process. Recently, iChEM researchers Professor Wu Yuen from the University of Science and Technology of China collaborated with the Associate Professor Duan Xuezhi of the East China University of Science and Technology is synthesized a tetra-nitrogen-coordinated Ru single atom catalyst based on the new non-carbon phosphorus nanotube carrier by the traditional co-reduction method. For acid test, The Ru single atoms on the PN matrix catalyst exhibits low overpotentials at 10 mA/cm2 (24 mV in 0.5m H2SO4 solution), a Tafel slope of 38 mV/dec, and robust stability at large current density. Furthermore, Density functional theory calculations have demonstrated that the adsorption of H* on PN matrix is closer to zero than those of Ru/C, Ru SAs@C3N4, and Ru SAs@C, thus resulting in a mediated adsorption–desorption behavior of Ru SAs@PN to facilitate the overall HER performance.

Schematic diagram of synthesis of Ru single atom on phosphorus nitride support

This work provides a new idea for the design of single atom catalyst supports, while revealing that the Ru single atom on PN matrix catalyst exhibit excellent activity and stability in acidic hydrogen evolution reactions. Related work is entitled "Efficient and Robust Hydrogen Evolution: Phosphorus Nitride Imide Nanotubes as Supports for Anchoring Single Ruthenium Sites", published on Angew. Chem. Int. Ed. (201804854).
(DOI: 10.1002/anie.201804854)

This work was supported by National Key R&D Program of China and the National Natural Science Foundation of China. We thank the photoemission endstations BL1W1B in Beijing Synchrotron Radiation Facility (BSRF), BL14W1 in Shanghai Synchrotron Radiation Facility (SSRF), BL10B and BL11U in National Synchrotron Radiation Laboratory (NSRL), for the help with characterization.

Paper link：https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201804854