Ligand-controlled synthesis of high density and ultra-small Ru nanoparticles with excellent electrocatalytic hydrogen evolution performance

Ultra-small size metal nanoparticles (u-MNPs) have broad applications in the fields of catalysis, biomedicine and energy conversion. Herein, by means of a ligand-controlled synthesis strategy, series of Ru-based NPs with high dispersity and ultra-small size (marked as u-Ru/C), or sparse and aggregated state (marked as a-Ru/C) anchored on the surface of hollow porous carbon shells are prepared. Systematical in-situ thermogravimetry-mass spectrometry-Fourier transform infrared spectra tests suggest that the different ligands in these Ru-based precursors can regulate the nucleation, growth and fixation of metal sites during the pyrolysis process, thus contributing to Ru NPs with various size and dispersity. As a result, when applied to hydrogen evolution reaction, the u-Ru-1/C catalyst displays a low Tafel slope of 26 mV.dec(-1), overpotential of 31 mV (at 10 mA.cm(-2)) and a large exchange current density of 1.7 mA.cm(-2) in 1.0 M KOH, significantly better than that of the a-Ru-2/C, hollow carbon and even commercial 20% Pt/C. This is mainly because that the u-Ru-1/C sample owns both smaller particle size, more electrochemical active sites, higher intrinsic activity and optimized surface H adsorption ability than that of the a-Ru-2/C counterpart. Such ligand-modulated growth strategy is not only applicable to Ru, but also can be extended to other similar metals, offering a step forward in the design and synthesis of highly dispersed u-MNPs.

Automated summary

Using a ligand-controlled synthesis strategy, highly dispersed and ultra-small size Ru-based nanoparticles were successfully prepared and exhibited excellent performance in the hydrogen evolution reaction. Additionally, the study revealed that different ligands in metal precursors can regulate the nucleation, growth, and fixation of metal sites during the pyrolysis process.