Subscriber access provided by Kaohsiung Medical University
Article
Anisotropic surface modulation of Pt catalysts for highly reversible Li-O2 batteries; High index facet as a critical descriptor Kyeongse Song, Jaepyeong Jung, Mihui park, Hyeokjun Park, Hyung-Jin Kim, Sang-Il Choi, Junghoon Yang, Kisuk Kang, Young-Kyu Han, and Yong-Mook Kang ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b02172 • Publication Date (Web): 17 Aug 2018 Downloaded from http://pubs.acs.org on August 17, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Anisotropic surface modulation of Pt catalysts for highly reversible Li-O2 batteries; High index facet as a critical descriptor Kyeongse Song,1,‡ Jaepyeong Jung,1,‡ Mihui Park,1,‡ Hyeokjun Park,2 Hyung-Jin Kim,1 Sang-Il Choi,3 Junghoon Yang,1 Kisuk Kang,2 Young-Kyu Han,1,* and Yong-Mook Kang1,* 1
Department of Energy and Materials Engineering, Dongguk University-Seoul Pildong-ro 30,
Jung-gu, Seoul, 04620, Republic of Korea. 2
Department of Materials Science and Engineering, Research Institute of Advanced Materials
(RIAM), Seoul National University Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea. 3
Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National
University, Daehakro 80, Bukgu, Daegu 41566, Republic of Korea.
ACS Paragon Plus Environment
1
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 37
ABSTRACT: The surface structure of solid catalysts has been regarded as a critical descriptor for determining the catalytic activities in various applications. However, structure-dependent catalytic activities have been rarely understood for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) within Li-O2 batteries. Here, we succeeded in the preparation of a Pt catalyst with an anisotropic structure and demonstrated its high catalytic activity in nonaqueous Li-O2 batteries. The cathode incorporating Pt exposed with high-index {411} facets showed greatly enhanced ORR and OER performance in comparison to commercial Pt/C cathode. The anisotropic Pt catalyst improved ORR activity with a large capacity of 12,985 mAh gcarbon-1, high rate performance, and stable cyclic retention up to 70 cycles with the capacity limited to 1,000 mAh gcarbon-1 of capacity. Furthermore, the anisotropic Pt catalyst exhibited high round-trip efficiency of ~87% with a low OER potential (3.1 V) at a current density of 200 mA gcarbon-1. Our first-principles calculations revealed that the high-index facets, which contain step edge, kink, and ledge sites, are significantly more reactive than the low-index facets in terms of surface energy and O-binding energy.
KEYWORDS: oxygen reduction reaction, oxygen evolution reaction, anisotropic surface, high index facet, electrocatalyst, Li-O2 battery
ACS Paragon Plus Environment
2
Page 3 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
■ INTRODUCTION Li-O2 batteries have been regarded as a promising next-generation battery for electric vehicles and energy storage systems due to their huge energy density, which is derived from Li oxidation to form insoluble lithium peroxide as the discharge reaction (2Li+ + O2 + 2e− → Li2O2, E° = 2.96 V vs. Li/Li+).1-7 During the charge process, Li2O2 should be completely decomposed for reversible long-term cycling. However, several critical obstacles are encountered, including the instability of the reaction8-13 and high overpotential owing to sluggish ORR and/or OER,14-18 which limit the practical applications of Li-O2 batteries. In particular, OER overpotential is mainly attributed to insoluble deposition and dense stacking of the insulating discharge products, including Li2O2, which impede Li+ ion diffusion and e− transport resulting in drastic cyclic degradation.19-24 Hence, well-designed catalysts have been regarded as one of the key solutions to overcome these drawbacks. Based on the Sabatier principle, noble metals have received much academic interest as catalysts in Li-O2 batteries, since their intrinsic half-filled anti-bonding states can have proper adsorption interaction with the discharge products.25 Accordingly, the electronic band structure of the platinum (Pt) family of metal catalysts determines its catalytic activities in a volcanoshape trend. Therefore, one of the promising strategies to improve catalytic activity is alloying with other metals or metal oxides for controlling the surface composition of catalysts. For Ptbased alloys, the Shao-Horn group demonstrates that PtAu nanoparticles have bifunctional catalytic activity for ORR/OER, which achieved a high round-trip efficiency of 76% with an average voltage gap of ~0.85 V at a current density of 50 mA gcarbon-1.26 Thereafter, our group investigated the relationship between the catalytic activity of PdCu nanoparticles and the change of the electronic structure via the Cu atoms.27 The PdCu exhibits a high round-trip efficiency of
ACS Paragon Plus Environment
3
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 37
80% with an average voltage gap of ~0.66 V at a current density of 200 mA gcarbon-1, which is attributed to higher electron density of Pd on the top-layer (donated by the underlying Cu atoms), thereby decreasing the adsorption strength of LiO2 on the PdCu surface via electrostatic repulsion as elucidated by first-principles calculations. Kim et al. also claimed that the catalytic activity of Pt3Co alloy is inversely correlated to the adsorption strength of LiO2 on the alloy surface as consistent with the calculated overpotentials.28 Thus, Pt3Co nanoparticles achieved a high round-trip efficiency of 83% (average potential difference of about 0.56 V) at a current density of 200 mA gcarbon-1. Another potential strategy is to change the shape of the catalyst to mediate the surface atomic arrangement and coordination.18,24 This approach is well-documented for metal oxide catalysts in Li-O2 battery.18,24,29,30 For example, the spinel Co3O4 with different surface atomic arrangements via morphological change show significantly improved catalytic activities.24,31,32 Su et al. reported on the catalytic activities of nanometer-sized single crystals of Co3O4 toward Li-O2 battery, where they found the catalytic activity to be dependent on the surface termination in the order of {100}
