Atomically controllable in-situ electrochemical treatment of metal-organic-framework-derived cobalt-embedded carbon composites for highly efficient electrocatalytic oxygen evolution

• Published in: Applied surface science 2021-07, Vol.554, p.149651, Article 149651
• Main Authors: Ahn, Cheol Hyoun, Deshpande, Nishad G., Lee, Ho Seong, Cho, Hyung Koun
• Format: Article
• Language: English
• Subjects: Catalytic Co3+/Co4+ couple exchange states; Co-embedded nitrogen-doped carbon; In-situ electrochemical treatment; Metal-organic-framework; Oxygen evolution reaction
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2021.149651

[Display omitted] •Atomically controllable in-situ electrochemical treatment is designed.•The surface of Co was converted to catalytic Co3+/Co4+ couple exchange states.•The Co/CoOOH core/shell nanoparticles embedded carbon composite were formed.•Electrochemically designed catalysts exhibit excellent electrocatalytic performance. Co-based metal-organic frameworks (Co-MOFs) have attracted significant interest as intermediate templates to obtain Co-embedded nitrogen-doped carbon (NC) composites for highly catalytic oxygen evolution reaction. However, the electrocatalytic performance of Co-MOF-derived composite (Co@NC) for oxygen evolution remains unsatisfactory owing to its insufficient active sites and the detachment of Co nanoparticles. As catalytic reactions are mostly dominated by surface atoms, it is important to artificially control the surface catalytic sites of Co@NC composites to obtain highly efficient electrocatalysts. Herein, we proposed an in-situ electrochemical treatment to change the surface of Co nanoparticles to catalytic Co3+/Co4+ couple exchange states, thus obtaining a core/shell structure consisting of conductive Co metal and a highly active CoOOH layer. To achieve this, pyrolyzed Co@NC composites were subjected to a two-step in-situ electrochemical treatment; in the first step, the naturally formed inactive oxidation states were removed, and in the second step, the core/shell-structured nanoparticles were formed. The electrochemically designed Co@NC composite exhibited excellent electrocatalytic reaction with desirable overpotential (η10 = ~320 mV) and Tafel slope (78–80 mV·dec−1), in addition to long-term durability.