Small-Sized Tungsten Nitride Particles Strongly Anchored on Carbon Nanotubes and their Use as Supports for Pt for Methanol Electro-oxidation

The anchoring of small-sized WN (tungsten nitride) nanoparticles (NPs) with good dispersion on carbon nanotubes (CNTs) offers an effective means of obtaining promising materials for use in electrocatalysis. Herein, an effective method based on grinding treatment followed by a nitridation process is proposed to realize this goal. In the synthesis, a solution containing H-4[SiO4(W3O9)(4)] (SiW12) and CNTs modified with polyethylenimine (PEI-CNTs) was ground to dryness. Small-sized WN NPs were anchored onto the CNTs with good dispersion after calcination under NH,. Under hydrothermal assembly conditions (absence of grinding), WN particles of larger size and with inferior dispersion were obtained, demonstrating the important role of the grinding process. The benefit of the small-sized WN has been demonstrated by using WN/CNTs as a support for Pt to catalyze the methanol electro-oxidation reaction. The mass activity of Pt-WN/CNTs-G-70 (where G denotes the grinding treatment, and 70 is the loading amount (%) of WN in the WN/CNTs) was evaluated as about 817 mA mg(-1) p(L)' better that those of commercial Pt/C (340 mA mg p(L)) and Pt/CNTs (162 mA mg(-1) (pt)). The Pt-WN/CNTs-G also displayed good CO tolerance. In contrast, Pt-WN/CNTs prepared without the grinding process displayed an activity of 344 mA mg(-1) (pt) verifying the key role of grinding treatment in the preparation of WN/CNTs with good co-catalytic effect.