Hydrogen Vanadate as an Effective Stabilizer of Pd Nanocatalysts for Formic Acid Electroxidation

In this paper, a simple chemical reduction route is discussed that results in small size, uniform dispersion of Pd nanoparticles supported on carbon black. HVO42-, the tridentate oxoanion with its O-O distance of 2.76 angstrom, closely matching with the Pd-Pd distance (2.75 angstrom), is expected to be an effective stabilizer for Pd according to the lattice size-matching binding model (Finke, R. G.; Ozkar, S. Coord. Chem. Rev. 2004, 248, 135). Because it has never been tested, HVO42- is exploited and found to be a very simple and effective stabilizer. TEM shows the formation of dispersed Pd nanoparticles supported on carbon with an average particle size of 4.8 nm and rather narrow size distribution. Adsorbed HVO42- can be completely removed after Pd reduction by simply washing with water, as indicated by EDX measurement. The Pd/C catalyst thus prepared shows greatly enhanced activities for the HCOOH electrooxidation reaction compared to catalyst commonly reduced by NaBH4 due to the size reduction of Pd and the uniform distribution. The chemical reduction route of Pd/C catalyst with HVO42- as stabilizer is very simple and has great potentials for mass-producing Pd/C and others noble metal catalysts.