Enhanced electrocatalytic activity of platinum supported on nitrogen modified ordered mesoporous carbon

摘要

Nitrogen-modified ordered mesoporous carbon is synthesized via the 900 C carbonization of polyaniline-coated mesoporous carbon. The electronic states of nitrogen atoms are investigated by XPS technique. Pyridinic nitrogen and quaternary nitrogen generate disorders and curvatures on the surface of graphitic carbon layers with nitrogen atoms replacing carbon atoms at the edges and the interior of carbon stacking, and thus offering beneficial anchoring sites for PtCl_6~(2-) ions. Pyridinic nitrogen and pyrrolic nitrogen offer p electrons to the sp~2 hybridized graphitic carbon layers, decreasing the inner electrical resistance of the catalytic carbon layer, enhancing the rate of proton diffusion, and transporting more free electrons to oxidative platinum. Due to the advantageous modification of the electronic structure of carbon atoms, platinum nanoparticles with a narrow size distribution are homogenously dispersed onto the surface of nitrogen-modified ordered mesoporous carbon, as evidenced by TEM images. Electrochemical tests show that the samples loaded platinum calcined at the 900°C exhibit the optimum loading performance among as-made catalysts and a gradually decreased decay in electro-catalytic activity with time, with the current density stabilized at 3.64 mA cm~(-2), which is far higher than that of mesoporous carbon (0.15 mA cm~(-2)).