Epitaxial growth of oriented prussian blue analogue derived well-aligned CoFe2O4 thin film for efficient oxygen evolution reaction

The development of cost-effective, high-efficiency, and non-noble metal based electrocatalysts for oxygen evolution reaction (OER) is considered to be the most pivotal portion for electrochemical water splitting to generate renewable energy. Herein, well-aligned mesoporous CoFe2O4 thin film is first developed from surface epitaxial growth of oriented CoFe-based Prussian blue analogue thin film (CoFe-PBA thin film) for efficient electrocatalytic OER. CoFe-PBA thin film with preferred [100] orientation is first prepared on the substrate surface by employing liquid phase epitaxial method without any structure-directing surfactants. After thermal pyrolysis, such CoFe-PBA thin film was transformed into well-aligned mesoporous CoFe2O4 thin film. Interestingly, the self-support CoFe3O4 thin film electrode with the mass loading of 1.6 mg cm-2 delivers an oxygen evolution current density of 10 mA cm-2 at an overpotential of 266 mV and exhibits durable stability in 1 M KOH aqueous solution. The remarkable and stable catalytic performance of the CoFe2O4 thin film can be mainly owing to the mesoporous structure of CoFe2O4, efficient charge/electron transfer, the numerous exposed active sites, and the well-structured configuration of the electrode. Hence, this work provides an effective paradigm for preparing binder-free, self-support, and low-cost spinel oxide electrocatalyst for efficient OER derived from surface epitaxial growth of oriented PBA thin film.