Mixed Carbon-Graphene Supports for Cobalt (II) Phthalocyanine as Fuel Cell Cathode

Cobalt (II) phthalocyanine (CoPc) supported on graphene (CVD), carbon black (Vulcan XC72), multi walled carbon nanotube (MWCNT) and their mixtures were evaluated as electrocatalysts for oxygen reduction reaction in acid electrolytes and polymer electrolyte membrane fuel cells (PEMFC). Graphene (G) and carbon supported CoPc catalysts were prepared by impregnation method. Three different temperatures (800 C, 650 C and 500 C) were studied to examine the effect of heat treatment on CoPc and the best fuel cell performance was obtained with samples heat-treated at 800 C. Maximum power densities of CoPc/G, CoPc/Vulcan-G, CoPc/MWCNT-G, CoPc/MWCNT, CoPc/Vulcan and CoPc/Vulcan-MWCNT at 60 C cell temperature, 100% humidity and 5 psi back pressure were found as 102, 171, 179, 189, 296, 303 mW cm^-2, respectively. CVD graphene with CoPc was forming impermeable layer-structure causing mass transport limitations and lower performance. Performance enhancements were achieved by heat-treatment of the samples, higher catalyst loading, operating at high temperatures and higher pressures under 100% humidity. Hybridization of CVD graphene with Vulcan and MWCNT led improved fuel cell performance at 25 psi back pressure compare to individual support materials.