Microporous 3D-Structured Hierarchically Entangled Graphene-Supported Pt3Co Alloy Catalyst for PEMFC Application with Process-Friendly Features.

Abstract

To improve the oxygen reduction reaction (ORR) performance in a proton-exchange membrane fuel cell (PEMFC) cathode with respect to mass activity and durability, a suitable electrocatalyst design strategy is essentially needed. Here, we have prepared a sub-three nm-sized platinum (Pt)-cobalt (Co) alloy (Pt3Co)-supported N-doped microporous 3D graphene (Pt3Co/pNEGF) by using the polyol synthesis method. A microwave-assisted synthesis method was employed to prepare the catalyst based on the 3D porous carbon support with a large pore volume and dense micro-/mesoporous surfaces. The ORR performance of Pt3Co/pNEGF closely matches with the state-of-the-art commercial Pt/C catalyst in 0.1 M HClO4, with a small overpotential of 10 mV. The 3D microporous structure of the N-doped graphene significantly improves the mass transport of the reactant and thus the overall ORR performance. As a result of the lower loading of Pt in Pt3Co/pNEGF as compared to that in Pt/C, the alloy catalyst achieved 1.5 times higher mass activity than Pt/C. After 10,000 cycles, the difference in the electrochemically active surface area (ECSA) and half-wave potential (E1/2) of Pt3Co/pNEGF is found to be 5 m2 gPt-1 (ΔECSA) and 24 mV (ΔE1/2), whereas, for Pt/C, these values are 9 m2 gPt-1 and 32 mV, respectively. Finally, in a realistic perspective, single-cell testing of a membrane electrode assembly (MEA) was made by sandwiching the Pt3Co/pNEGF-coated gas diffusion layers as the cathode displayed a maximum power density of 800 mW cm-2 under H2-O2 feed conditions with a clear indication of helping the system in the mass-transfer region (i.e., the high current dragging condition). The nature of the I-V polarization shows a progressively lower slope in this region of the polarization plot compared to a similar system made from its Pt/C counterpart and a significantly improved performance throughout the polarization region in the case of the system made from the Pt3Co/NEGF catalyst (without the microwave treatment) counterpart. These results validate the better process friendliness of Pt3Co/pNEGF as a PEMFC electrode-specific catalyst owing to its unique texture with 3D architecture and well-defined porosity with better structural endurance.