Carbon-supported ultrafine Pt nanoparticles modified with trace amounts of cobalt as enhanced oxygen reduction reaction catalysts for proton exchange membrane fuel cells

To accelerate the kinetics of the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells,ultrafine Pt nanoparticles modified with trace amounts of cobalt were fabricated and decorated on carbon black through a strategy involving modified glycol reduction and chemical etching.The obtained Pt36Co/C catalyst exhibits a much larger electrochemical surface area(ECSA)and an improved ORR electrocatalytic activity compared to commercial Pt/C.Moreover,an electrode prepared with Pt36Co/C was further evaluated under H2-air single cell test conditions,and exhibited a maximum specific power density of 10.27 W mgPt^-1,which is 1.61 times higher than that of a conventional Pt/C electrode and also competitive with most state-of-the-art Pt-based architectures.In addition,the changes in ECSA,power density,and reacting resistance during the accelerated degradation process further demonstrate the enhanced durability of the Pt36Co/C electrode.The superior performance observed in this work can be attributed to the synergy between the ultrasmall size and homogeneous distribution of catalyst nanoparticles,bimetallic ligand and electronic effects,and the dissolution of unstable Co with the rearrangement of surface structure brought about by acid etching.Furthermore,the accessible raw materials and simplified operating procedures involved in the fabrication process would result in great cost-effectiveness for practical applications of PEMFCs.

Wavy PtCu alloy nanowire networks with abundant surface defects enhanced oxygen reduction reaction

Bimetalic platinum-copper(Pt-Cu)alloy nanowires have emerged as a novel class of fuel cell electrocatalysts for oxygen reduction reaction(ORR)due to their intrinsic high catalytic activity and durability,but preparing such electrocatalysts with clean surface via facile method is still a challenge.Herein,PtCu alloy with nanowire networks(NWNs)structure is obtained by a simple modified polyol method accompanied with a salt-mediated self-assembly process in a water/ethylene glycol(EG)mixing media.The formation mechanism of PtCu NWNs including the morphological evolution and the relevant experimental parameters has been investigated systematically.We propose that a micro-interface in H2O-EG media formed with the assistance of disodium dihydrogen pyrophosphate(Na2H2P2O7)and its unique nature of coordinating with Pt^2+ or Cu^2+ play critical roles in the formation of NWNs.When tested as ORR catalyst,the PtCuNWNs/C exhibits much higher activity and durability than that of PtNWNs/C and commercial PtC,even exceeding the target of DOE in 2020.The excellent performance of PtCuNWNs/C could be attributed to the unique structure of NWNs with 2.4 nm ultrathin wavy nanowires and plentiful surface defects and the modified electronic effect caused by alloying with Cu atoms.

Enhanced electrocatalytic performance of ultrathin PtNi alloy nanowires for oxygen reduction reaction

In this paper, ultrathin Pt nanowires （Pt NWs） and PtNi alloy nanowires （PtNi NWs） supported on carbon were synthesized as electrocatalysts for oxygen reduction reaction （ORR）. Pt and PtNi NWs catalysts composed of interconnected nanoparticles were prepared by using a soft template method with CTAB as the surface active agent. The physical characterization and electrocatalytic perfor- mance of Pt NWs and PtNi NWs catalysts for ORR were investigated and the results were compared with the commercial Pt/C catalyst. The atomic ratio of Pt and Ni in PtNi alloy was approximately 3 to 1. The results show that after alloying with Ni, the binding energy of Pt shifts to higher values, indicating the change of its electronic structure, and that Pt3Ni NWs catalyst has a significantly higher electrocatalytic activity and good stability for ORR as compared to Pt NWs and even Pt/C catalyst. The enhanced electrocatalytic activity of Pt3Ni NWs catalyst is mainly resulted from the downshifted-band center of Pt caused by the interaction between Pt and Ni in the alloy, which facilitates the desorption of oxygen containing species （Oads or OHads） and the release of active sites.