title: Engineering Bimetallic Ag-Cu Nanoalloys for Highly Efficient Oxygen Reduction Catalysts: A Guideline for Designing Ag-Based Electrocatalysts with Activity Comparable to Pt/C-20.
abstract: Development of highly active and stable Pt-free oxygen reduction reaction catalysts from earth-abundant elements remains a grand challenge for highly demanded metal-air batteries. Ag-based alloys have many advantages over platinum group catalysts due to their low cost, high stability, and acceptable oxygen reduction reaction (ORR) performance in alkaline solutions. Nevertheless, compared to commercial Pt/C-20%, their catalytic activity still cannot meet the demand of commercialization. In this study, a kind of catalysts screening strategy on AgxCu100-xnanoalloys is reported, containing the surface modification method, studies of activity enhancement mechanism, and applied research on zinc-air batteries. The results exhibit that the role of selective dealloying (DE) or galvanic displacement (GD) is limited by the "parting limitation", and this "parting limitation" determines the surface topography, position of d-band center, and ORR performance of AgxCu100-xalloys. The GD-Ag55Cu45and DE-Ag25Cu75catalysts alloys present excellent ORR performance that is comparable to Pt/C-20%. The relationship between electronic perturbation and specific activity demonstrates that positive shift of the d-band center (≈0.12 eV, relative to Ag) for GD-Ag55Cu45is beneficial for ORR, which is contrary to Pt-based alloys (negative shift, ≈0.1 eV). Meanwhile, extensive electrochemical and electronic structure characterization indicates that the high work function of GD-Ag55Cu45(4.8 eV) is the reason behind their excellent durability for zinc-air batteries.
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian, 710072, China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian, 710072, China.
authors.forename: Fuyi
authors.initials: F
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian, 710072, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian, 710072, China.
authors.forename: Adnan
authors.initials: A
authors.lastname: Qaseem
authors.affiliation: School of Chemistry, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Roy L
authors.initials: RL
authors.lastname: Johnston
keywords: Ag-based alloys; d-band center; electronic perturbation; oxygen reduction; parting limitation