Role of crystal structure and electrical polarization of an electrocatalyst in enhancing oxygen evolution performance: Bi-Fe-O system as a case study. (1st March 2022)

• Record Type: Journal Article
• Authors: Vijay, Aditi; Ramanujachary, K.V.; Lofland, Samuel E.; Vaidya, Sonalika
• Is Part Of: Electrochimica acta. Volume 407(2022)
• Publication Date: 2022-03-01
• Subjects: BiFeO3 -- Bi2Fe4O9 -- Bi25FeO40 -- Crystal structure -- Electrical polarization -- Oxygen evolution reaction; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2022.139887
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Orthorhombic Bi2 Fe4 O9 exhibited highest OER activity amongst three Bi-Fe-O. Lowest charge transfer resistance; highest double-layer capacitance for Bi2 Fe4 O9 . Performance of Bi2 Fe4 O9 attributed to Feoct -O-Fetd linkages, plate-like morphology. OER activity increased by factor of 4 after electrical polarization for Bi25 FeO40 . Abstract: This work aims to give an insight into the influence of crystal structure (for a system containing same elements but crystallizing in different structures) and the effect of electrical polarization on these oxides on the performance of oxygen evolution reaction (OER). We have tried to highlight this influence by taking the Bi-Fe-O system for the study. Herein, we have synthesized three structures of the Bi-Fe-O system viz. BiFeO3 (perovskite structure), Bi2 Fe4 O9 (mullite structure), and Bi25 FeO40 (sillenite structure) as an example to establish the relation. These oxides were characterized by Rietveld refinement for structure and scanning electron microscopy (SEM) for morphology. Their optical and magnetic properties were also investigated. Systematic studies were carried out with both as-synthesized and electrically polarized oxides for their performance towards OER. We observed that the order for OER activity (using non-polarized catalyst) of the three stable structures synthesized was Bi2 Fe4 O9 > BiFeO3 > Bi25 FeO40, which was attributed to the presence of Fe(oct) -O-Fe(td) linkages in Bi2 Fe4 O9 . While the current density of Bi2 Fe4 O9 and BiFeO3 remained unchanged after poling, that of Bi25 FeO40 increased by four-fold. From the study, we have demonstrated that proper choice of the crystal structure and utilization of electrical polarization can be effective strategies to manipulate the surfaces of an electrocatalytic material. Graphical abstract: Image, graphical abstract