title: Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells.
abstract: Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I(-)/I3 (-)) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I(-)/I3 (-) and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy)3 (2+/3+) (bpy = 2,2'-bipyridine) and I(-)/I3 (-) electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE-based DSSCs displayed a higher photovoltaic performance than did the Pt-CE-based DSSCs in both SM315 sensitizer with Co(bpy)3 (2+/3+) and N719 sensitizer with I(-)/I3 (-) electrolytes. Furthermore, the I3 (-) reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green's function calculations.
authors.affiliation: School of Energy and Chemical Engineering, Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: Myung Jong
authors.initials: MJ
authors.lastname: Ju
authors.affiliation: School of Energy and Chemical Engineering, Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: In-Yup
authors.initials: IY
authors.lastname: Jeon
authors.affiliation: Global GET-Future Laboratory and Department of Advanced Materials Chemistry, Korea University, 2511 Sejong-ro, Sejong 339-700, Korea.
authors.forename: Hong Mo
authors.identifier: 0000-0002-1901-2699
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 305-701, Korea.
authors.forename: Ji Il
authors.identifier: 0000-0002-5366-7066
authors.initials: JI
authors.lastname: Choi
authors.affiliation: School of Energy and Chemical Engineering, Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: Sun-Min
authors.initials: SM
authors.lastname: Jung
authors.affiliation: School of Energy and Chemical Engineering, Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Seo
authors.affiliation: Global GET-Future Laboratory and Department of Advanced Materials Chemistry, Korea University, 2511 Sejong-ro, Sejong 339-700, Korea.
authors.forename: In Taek
authors.initials: IT
authors.lastname: Choi
authors.affiliation: Global GET-Future Laboratory and Department of Advanced Materials Chemistry, Korea University, 2511 Sejong-ro, Sejong 339-700, Korea.
authors.forename: Sung Ho
authors.identifier: 0000-0002-7089-8085
authors.initials: SH
authors.lastname: Kang
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 305-701, Korea.
authors.forename: Han Seul
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 305-701, Korea.
authors.forename: Min Jong
authors.initials: MJ
authors.lastname: Noh
authors.affiliation: Department of Energy and Materials Engineering, Dongguk University, 30 Pildong-ro 1-gil, Junggu, Seoul 04620, Korea.
authors.forename: Jae-Joon
authors.identifier: 0000-0001-8966-0336
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: UNIST Central Research Facilities (UCRF), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: Hu Young
authors.initials: HY
authors.lastname: Jeong
authors.affiliation: Global GET-Future Laboratory and Department of Advanced Materials Chemistry, Korea University, 2511 Sejong-ro, Sejong 339-700, Korea.
authors.forename: Hwan Kyu
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 305-701, Korea.
authors.forename: Yong-Hoon
authors.identifier: 0000-0001-5209-4908
authors.initials: YH
authors.lastname: Kim
authors.affiliation: School of Energy and Chemical Engineering, Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50, UNIST, Ulsan 689-798, Korea.
authors.forename: Jong-Beom
authors.initials: JB
authors.lastname: Baek
mesh_terms: D000465:Algorithms; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry; D004396:Coloring Agents; D004566:Electrodes; D004573:Electrolytes; D006108:Graphite / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D049329:Nanostructures / Q000737:chemistry*; D010084:Oxidation-Reduction; D012643:Selenium / Q000737:chemistry*; D012993:Solar Energy
chemical_list: D004396:Coloring Agents; D004573:Electrolytes; D003035:Cobalt; D006108:Graphite; D007455:Iodine; D012643:Selenium
keywords: Cobalt reduction reaction; Dye-sensitized solar cell; Edge-selenation; Graphene naoplatelet; Iodine reduction reaction