On the viability of chitosan-derived mesoporous carbons as supports for PtCu electrocatalysts in PEMFC

Chitosan is an abundant and non-toxic natural polysaccharide rich in nitrogen, which is used here to obtain Ndoped mesoporous carbons (NMCs) as supports for Pt-saving PtCu alloy elecrocatalysts, which can be of interest for low-temperature fuels cells. NMCs with different textural properties were synthesized from cheap silica templates. They presented relative dominance of disordered graphitic lattice and comparable amounts of pyrrolic and pyridinic N, with different specific BET surface areas (715-1040 m2 g-1) and mesopore (1.2-2.4 cm3 g-1) and micropore volumes (0.1-0.6 cm3 g-1). PtCu nanoparticles were deposited by Cu electroless deposition and further galvanic exchange with Pt, with overall Pt loadings about 20 wt.%. Pt-rich PtCu alloy crystallites with contracted Pt fcc lattices and sizes of 3.1-4.7 nm were formed. The synthesized PtCu/NMCs catalysts presented better specific current densities for the oxygen reduction and better CO tolerance and specific current densities for the methanol oxidation reaction than those of commercial Pt/C and PtCu/CMK-3. The PtCu/NMC prepared with the H2SO4-activated NMC was the most active catalyst. The different textural properties of the carbonaceous materials appeared to determine the surface structure of the PtCu nanoparticles.