Redox-state modulated ORR activity of Cd-based Prussian blue analog frameworks transformed via anion exchange with controlled redox-state from CdCO3 cuboids

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2019-08, Vol.847, p.113179, Article 113179
• Main Authors: Shrestha, Nabeen K., Bui, Hoa Thi, Yoon, Seog Joon, Patil, Supriya A., Bathula, Chinna, Lee, Kiyoung, Noh, Yong-Young, Han, Sung-Hwan
• Format: Article
• Language: English
• Subjects: Anion exchanging; Aqueous solutions; Cadmium; Catalysis; Catalytic activity; Cd-hexacyanoferrate frameworks; Chemical transformation; Electrocatalysis; Iron cyanides; Organic chemistry; ORR; Oxygen reduction reactions; Photoelectrons; Pigments; Potassium ferricyanide; Redox-state specific; Thin films; Transformations
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2019.05.061

This work reports a facile solution based chemical transformation of thin film of CdCO3 cuboids into Cd-based Prussian blue analogue structured thin film with controlled redox-state by manipulating the anion exchange reaction between the solid film and the aqueous solution of K3[Fe(CN)6] at 60°C. The progress of the transformation reaction is monitored via electron microscopy, X-ray difractometry and X-ray photoelectron spectroscopy. Based on the scenario of the reaction progress revealed by these analysis, the CdCO3 cuboids are first found to be transformed into the smaller cuboids of cadmium ferricyanide, which, on further reaction, are transformed into the cadmium ferrocyanide cuboids. Thus, by controlling the redox-state of the Fe-metal center on the frameworks, the electrocatalytic activity of the frameworks on oxygen reduction reaction (ORR) is studied. The electrocatalytically inert CdCO3 cuboids after transformation to the frameworks with Fe3+-centers demonstrate an enhanced catalytic activity on ORR, while the Fe2+-centers of the frameworks are found to relegate the catalytic activity, thereby manifesting the redox-sate modulated ORR activity of the frameworks. To the best of the authors' knowledge, this is the first report of this kind on redox-state specific ORR activity. [Display omitted] •Conversion of CdCO3 cuboid film into Cd-HCF frameworks via anion exchange•Controlling reaction time to achieve Fe (III)-or Fe(II)- based Cd-HCF frameworks•Fe(III) based Cd-HCF frameworks demonstrate electrocatalytic activity towards ORR.•Fe(II) based Cd-HCF frameworks relegate the ORR catalytic activity.