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.

Research progress of Pt and Pt-based cathode electrocatalysts for proton-exchange membrane fuel cells

Proton-exchange membrane fuel cells(PEMFCs)have been widely used commercially to solve the energy crisis and environmental pollution.The oxygen reduction reaction(ORR)at the cathode is the rate-determining step in PEMFCs.Platinum(Pt)catalysts are used to accelerate the ORR kinetics.Pt’s scarcity,high cost,and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs.Therefore,studies should explore electrocatalysts with high catalytic activity,enhanced stability,and low-Pt loading.This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs,including anticorrosion catalyst supports,Pt,and Pt-based alloy electrocatalysts.Advanced preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.

Preparation and characterization of Ti_(0.7)Sn_(0.3)O_2 as catalyst support for oxygen reduction reaction

Sn-doped TiO2 nanoparticles with high surface area of 125.7 m2·g-1 are synthesized via a simple one-step hydrothermai method and explored as the cathode catalyst support for proton exchange membrane fuel cells.The synthesized support materials are studied by X-ray diffraction analysis,energy dispersive X-ray spectroscopy and transmission electron microscopy.It is found that the conductivity has been greatly improved by the addition of 30 mol%Sn and Pt nanoparticles are well dispersed on Ti0.7Sn0.3O2 support with an average size of 2.44 run.Electrochemical studies show that the Ti0.7Sn0.3O2 nanoparticles have excellent electrochemical stability under a high potential compared to Vulcan XC-72.The as-synthesized Pt/Ti0.7Sn0.3O2 exhibits high and stable electrocatalytic activity for the oxygen reduction reaction.The Pt/Ti0.7Sn0.3O2 catalyst reserves most of its electrochemically active surface area（ECA）,and its half wave potential difference is 11 mV,which is lower than that of Pt/XC-72（36 mV） under 10 h potential hold at 1.4 V vs.NHE.In addition,the ECA degradation of Pt/Ti0.7Sn0.3O2is 1.9 times lower than commercial Pt/XC-72 under 500 potential cycles between 0.6 V and 1.2 V vs.NHE.Therefore,the as synthesized Pt/Ti0.7Sn0.3O2 can be considered as a promising alternative cathode,catalyst for proton exchange membrane fuel cells.

Wormholelike mesoporous carbon supported Pt Ru catalysts toward methanol electrooxidation

Wormholelike mesoporous carbons (WMCs) with three different pore diameters (D-P), namely WMC-F7 (D-p = 8.5 nm), WMC-F30 (D-p =4.4 nm), and WMC-F0 (D-p =3.1 nm) are prepared via a modified sol-gel process. Then PtRu nanoparticles with the particle size (40 of 3.2 nm supported on WMCs are synthesized with a modified pulse microwave-assisted polyol method. It is found that the pore diameter of WMCs plays an important role in the electrochemical activity of PtRu toward alcohol electrooxidation reaction. PtRu/WMC-F7 with D-p > 2d(pt) exhibits the largest electrochemical surface area (ESA) and the highest activity toward methanol electrooxidation. With the decrease in Dp, PtRu/WMC-F30 and PtRu/WMC-F0 have much lower ESA and electrochemical activity, especially for the isopropanol electrooxidation with a larger molecular size. When D-p is more than twice d(pt), the mass transfer of reactants and electrolyte are easier, and thus more PtRu nanoparticles can be utilized and the catalysts activity can be enhanced. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

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.