Proton exchange membrane fuel cells show a lot of promise for portable green energy conversion devices, with possible applications in electric cars. However the cost associated with these devices is very high, mostly because of the use of large amounts of precious Pt, required as catalyst to achieve high electrochemical efficiency. Towards this end, bimetallic PtM, Pt alloyed with other transition metals (M=Co, Fe or Ni) show a lot of potential as a replacement. Achieving theoretically predicted efficiency has proven difficult because of the formation of oxides by the transition metals during solution-based synthesis, subsequently leading to its dissolution in acidic electrolytes. In a recent work published in NPG Asia Materials (www.nature.com/am/journal/v8/n1/full/am2015143a.html), hybrid organic-inorganic PtCo nanoparticles have been shown to exhibit high electrochemical efficiency and high resistance to erosion. Selectively modifying the surface of PtCo nanoparticles with C-PNIPAM is shown to prevent the erosion of transition metal as well as increase the electrochemical efficiency. Researchers from IKST carried out state-of-the-art quantum mechanical calculations to explain the underlying mechanisms at the atomic scale responsible for the experimental observations.
Schematic diagram of the surface modification of PtCo nanoparticles using C-PNIPAM. The N moieties of amide functional groups in PNIPAM chain are expected to interact selectively with the surface Co atoms on the PtCo nanoparticles. The blue and yellow balls represent the Pt and Co atoms, respectively.
Simulated electronic structures of PtCo surfaces saturated with (a) OH and (b) NH3. The Electron distributions changed considerably on the PtCo surfaces when OH and NH3 was adsorbed on to the surfaces. Red and green indicate the electron gain and loss, respectively.