Improved Pt Dispersion by Modified Carbon Support with Low Surface Oxygen Content and Extra Mesopores

Abstract

Proton exchange membrane fuel cell (PEMFC) is an efficient, and clean energy conversion device. By now, PEMFC still costs highly because of its massive Pt usage to overcome the poor oxygen reduction reaction (ORR) rate in cathode. Modified carbon supports have endowed Pt-based catalysts with better ORR performance, generally by improvement of Pt dispersion. This work focuses on the change of surface oxygen content and pore structure on modified carbon to make clear their respective role in Pt dispersion. With three designed pretreatment routes, it has reasonably determined that surface oxygen content on carbon black (CB) negatively correlates with the Pt dispersion, while newly-generated 2-4 nm mesopores play a positive role. With low surface oxygen content and/or more 2-4 nm mesopores, modified CBs succeed to drive Pt nanoparticles to reach smaller mean diameters (e.g., 1.90 and 2.65 nm) and narrower diameter regions. Catalysts supported by the above modified CBs acquire better ORR performance (64 m2 gPt-1 for electrochemical surface area and 336 mA mgPt-1 for mass activity) and higher durability (14% decay for mass activity and 6 mV shift for half-wave potential) after accelerated durability tests for 30k cycles, compared with Pt/CB supported by pristine CB and commercial Pt/C.

Keywords: Carbon black, Surface oxygen content, Mesopores, ORR catalysts, PEMFC