Tungsten diselenide/porous carbon with sufficient active edge-sites as a co-catalyst/Pt-support favoring excellent tolerance to methanol-crossover for oxygen reduction reaction in acidic medium

Developing an acid-stable, highly active and methanol-tolerant electrocatalyst towards the oxygen reduction reaction (ORR) is crucial for commercialization of direct methanol fuel cells (DMFCs). In this study, via a simultaneous synthesis method, tungsten diselenide/porous carbon (WSe2/C) composites are prepared as the supports/ORR co-catalysts to support Pt with a low loading of 5 wt.%. Varied WSe2/C supports are obtained by tuning the carbonization temperature (600-1000 degrees C) to investigate the relationships between structural characteristics and ORR performance. Pt-WSe2/C (800 degrees C) exhibits a considerably higher specific activity (4.57 mA cm(-2)) for ORR than those of WSe2/C (2.45 mA cm(-2)) and commercial Pt/C (10 wt.%, 2.69 mA cm(-2)), owing to the high ORR co-catalytic activity of WSe2/C for Pt. The robust contacts among Pt, WSe2 and porous carbon with high surface area can significantly improve the exposure of Pt active sites, which correspondingly promote the charge transfer efficiency and the fast adsorption, activation and reduction of oxygen molecules. Moreover, Pt-WSe2/C (800 degrees C) catalyst exclusively exhibits a four electron pathway for ORR. With the intimate cooperation among Pt, WSe2 and porous carbon skeleton, more available Pt active sites are exposed to improve the ORR kinetics and durability. The tolerance to methanol-crossover on Pt-WSe2/C are remarkably enhanced, which should be attributed to the synergistic effects between the exposed edge sites of embedded WSe2 and the porous carbon skeleton with abundant oxygen-containing functional groups. The use of WSe2/C supports with low-cost, high cocatalytic/catalytic activity and strong methanol -tolerance provides a promising way to enhance ORR activity in DMFCs. (C) 2017 Elsevier B.V. All rights reserved.