A highly efficient and stable oxygen reduction reaction on Pt/CeOx/C electrocatalyst obtained via a sacrificial precursor based on a metal-organic framework

Advanced Pt/CeOx/C nanocomposite, where C = porous carbon and multi-walled carbon nanotube (MWCNT), was synthesized using a precursor based on Ce-containing metal organic framework (MOF), via carbonyl chemical route, followed by heat-treatment at 900 degrees C under argon atmosphere. Based on the analyses of powder X-ray diffraction (pXRD) data, and via the Williamson-Hall method, the lattice parameter, stacking fault and micro-strain values on Pt/CeOx/C was found to decrease, whereas the crystallite size increased with respect to the as-prepared sample. Combined with the results of transmission electron microscopy (TEM), these changes were related to the in-situ formation of intimately contacted Pt/CeOx nanoparticles (NPs), well-dispersed onto MWCNT support. However, both the pXRD and TEM results showed that the Pt NPs were agglomerated upon heating and finally detached from the support in the MOF-free samples. Thus, MOF could protect Pt nanoparticles (NPs) from agglomeration at high temperature. The X-ray photoelectron spectroscopy (XPS) showed that the Pt surface was less oxidized in Pt/CeOx/C nanocomposite in comparison to as-prepared and MOF-free samples. Moreover, only the Ce3+ was detected in the nanocomposite. These facts together with Raman spectroscopy and surface electrochemistry experiments assessed the stabilization of the electronic state of Pt degrees and Ce3+ via the interaction between Pt and CeOx. In addition, enhanced catalytic activity towards the oxygen reduction reaction (ORR) was observed in acid medium. The specific and mass activity at 0.9 V/RHE on Pt/CeOx/C were ca. 1279 mu A cm(pt)(-2) and 870 mA mg(pt)(-1), respectively, ca. 10-11 fold higher than commercial Pt/C (Johnson Matthey, JM) in half-cell. Accelerating durability tests (ADT), after 16,000 potential cycles, demonstrated higher stability of Pt/CeOx/C in contrast to oxide-free and Pt/C (JM) catalyst. Compared with other homemade or commercial Pt/C (JM) cathodes, the innovative cathode catalyst showed enhanced cell performance in a H-2/O-2 micro-laminar flow fuel cell system. (C) 2016 Elsevier B.V. All rights reserved.