Phosphotungstic acid-assisted preparation of carbon nanotubes-supported uniform Pt and Pt bimetallic nanoparticles, and their enhanced catalytic activity on methanol electro-oxidation

A 3–4 nm thickness of phosphotungstic acid (H3PW12O40, PW) layer is deposited on to the surface of multiwalled carbon nanotubes (MWCNTs) via sorption by ultrasonic method. These PW/MWCNT hybrids can be used as the promising supports for anode catalysts of the direct methanol fuel cell (DMFC). A facile polyol thermo-reduction method has been put forward to prepare PtIr (PtRu or Pt)/PW/MWCNT hybrids. In the presence of PW, PtIr (PtRu or Pt) nanoparticles can be uniformly dispersed on the surface of the MWCNTs in high density with a small size and a narrow distribution, and these Pt and Pt bimetallic catalysts exhibit a significantly improved electrochemically active surface area and a remarkably enhanced activity toward methanol oxidation. Besides, these Pt and Pt bimetallic catalysts on PW/MWCNT hybrids also show longer operation stability and higher CO tolerance as well as better cell performance compared with those on MWCNTs without PW. The evaluation of anode catalysts in DMFC indicates that the observed power density depends on the intrinsic property of the size, dispersion and composition of Pt and Pt bimetallic catalysts.