title: Self-Assembly of Spinel Nanocrystals into Mesoporous Spheres as Bifunctionally Active Oxygen Reduction and Evolution Electrocatalysts.
abstract: The present work introduces spinel oxide nanocrystals self-assembled into mesoporous spheres that are bifunctionally active towards catalyzing both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The electrochemical evaluation reveals that (Ni,Co)3O4demonstrates a significantly positive-shifted ORR onset and half-wave potentials [-0.127 and -0.292 V vs. saturated calomel electrode (SCE), respectively], whereas Co3O4results in a negative-shifted OER potential (0.65 V vs. SCE) measured at 10 mA cm-2. Based on the DFT analysis, the potential at which all oxygen intermediate reactions proceed spontaneously is the highest for (Ni,Co)3O4(U=0.66 eV) during ORR, whereas it is the lowest for Co3O4(U=2.09 eV) during OER. The high ORR activity of (Ni,Co)3O4is attributed to the enhanced electrical conductivity of the spinel lattice, and the high OER activity of Co3O4is attributed to relatively weak adsorption energy promoting rapid release of evolved oxygen.
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Dong Un
authors.initials: DU
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Jingde
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Moon Gyu
authors.initials: MG
authors.lastname: Park
authors.affiliation: Hydrogen & Fuel Cell Center, New & Renewable Energy Research Korea Institute of Energy Research (KIER), 20-41, Sinjaesaengeneogi-ro, Haseo-myeon, Buan-gun, Jellabuk-do, 56332, South Korea.
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Seo
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Wook
authors.initials: W
authors.lastname: Ahn
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Stadelmann
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Luis
authors.initials: L
authors.lastname: Ricardez-Sandoval
authors.affiliation: Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
authors.forename: Zhongwei
authors.identifier: 0000-0003-3463-5509
authors.initials: Z
authors.lastname: Chen
mesh_terms: D002384:Catalysis; D055664:Electrochemical Techniques; D004566:Electrodes; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D017382:Reactive Oxygen Species
keywords: bifunctional catalysts; density functional theory; oxygen evolution; oxygen reduction; spinel oxides