title: Ag-Sn Bimetallic Catalyst with a Core-Shell Structure for CO2Reduction.
abstract: Converting greenhouse gas carbon dioxide (CO2) to value-added chemicals is an appealing approach to tackle CO2emission challenges. The chemical transformation of CO2requires suitable catalysts that can lower the activation energy barrier, thus minimizing the energy penalty associated with the CO2reduction reaction. First-row transition metals are potential candidates as catalysts for electrochemical CO2reduction; however, their high oxygen affinity makes them easy to be oxidized, which could, in turn, strongly affect the catalytic properties of metal-based catalysts. In this work, we propose a strategy to synthesize Ag-Sn electrocatalysts with a core-shell nanostructure that contains a bimetallic core responsible for high electronic conductivity and an ultrathin partially oxidized shell for catalytic CO2conversion. This concept was demonstrated by a series of Ag-Sn bimetallic electrocatalysts. At an optimal SnOxshell thickness of ∼1.7 nm, the catalyst exhibited a high formate Faradaic efficiency of ∼80% and a formate partial current density of ∼16 mA cm-2at -0.8 V vs RHE, a remarkable performance in comparison to state-of-the-art formate-selective CO2reduction catalysts. Density-functional theory calculations showed that oxygen vacancies on the SnO (101) surface are stable at highly negative potentials and crucial for CO2activation. In addition, the adsorption energy of CO2-at these oxygen-vacant sites can be used as the descriptor for catalytic performance because of its linear correlation to OCHO* and COOH*, two critical intermediates for the HCOOH and CO formation pathways, respectively. The volcano-like relationship between catalytic activity toward formate as a function of the bulk Sn concentration arises from the competing effects of favorable stabilization of OCHO* by lattice expansion and the electron conductivity loss due to the increased thickness of the SnOxlayer.
authors.affiliation: Center of Catalytic Science and Technology, Department and Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Wesley
authors.initials: W
authors.lastname: Luc
authors.affiliation: Center of Catalytic Science and Technology, Department and Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Charles
authors.initials: C
authors.lastname: Collins
authors.affiliation: Department of Chemical Engineering, Virginia Polytechnic Institute and State University , Blacksburg, Virginia 24061, United States.
authors.forename: Siwen
authors.identifier: 0000-0003-3582-5398
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, Virginia Polytechnic Institute and State University , Blacksburg, Virginia 24061, United States.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Xin
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.|NUANCE Center, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: He
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.|Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China , Chengdu, Sichuan 610054, PR China.
authors.forename: Yijin
authors.initials: Y
authors.lastname: Kang
authors.affiliation: Center of Catalytic Science and Technology, Department and Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Feng
authors.identifier: 0000-0002-3335-3203
authors.initials: F
authors.lastname: Jiao