Wednesday, 31 May 2017: 16:20
Grand Salon B - Section 7 (Hilton New Orleans Riverside)
Proton exchange membrane fuel cells (PEMFCs) have attracted a lot of attention for alternative and green energy sources owning to their low-carbon emissions and high efficiencies. Pt-based electrocatalysts used in PEMFC electrodes are the main contributor to the high cost. More research focusing on the use of Pt group alloys is still required to achieve enhanced catalytic activity while decreasing the Pt loading. In this study, Pt-Ni binary catalysts by pulse electrodeposition and electroless-deposition process were developed for the enhancement of oxygen reduction reaction. The Pt-Ni catalysts were deposited on carbon nanotubes (CNTs) directly grown on carbon cloths. CNTs used for catalyst nanostructured supports can decrease the needs of Pt and improve the performance of fuel cells. The nickel nanoparticles were deposited on CNTs by pulse electro-planting to form large-area flake structures. Then the platinum nanoparticles were reduced on them in a potassium hydroxide solution containing platinum precursor and ethylene glycol at 75 oC for the deposition time of 3, 4, 5 hours. The sample with the commercial Pt/C and Pt/CNTs were also prepared for comparison. Structure and elementary composition of catalysts were measured by SEM, XRD and ICP-MS. Ni/CNTs sample showed a uniform distribution of Ni nanoparticles on the surface of CNTs, which was provided for the deposition of Pt nanoparticles with average particle size of about 5 nm. Electrochemical characteristics of PtNi/CNTs and Pt/CNTs samples were investigated via cyclic voltammetry (CV) analysis and rotating disk electrode (RDE) test in 0.1 M perchloric acid solution. In terms of both limiting current density and onset potential, the PtNi/CNTs samples were better than those of Pt/CNTs samples. All PtNi/CNTs samples with different Pt deposition time showed very similar LSV curves using RDE tests. In single cell test, the PtNi/CNTs, as the cathode catalyst, has a higher maximum power density (763 mW/cm2) than the commercial Pt/C. Among the PtNi/CNTs samples, the better performance of PtNi/CNTs sample with 4-hours Pt deposition time can be attributed to the more convenient Pt availability for the oxygen reduction reaction (ORR). It can be also found that the open circuit voltage of this sample could reach up to 1V due to a significant decrease of the polarization loss. The main outcome of this study was that Pt–Ni binary alloy catalysts had better oxygen reduction reaction for cathode of PEMFC.