Hexagonal perovskite Sr6(Co0.8Fe0.2)5O15 as an efficient electrocatalyst towards the oxygen evolution reaction

Abstract

The high overpotential required for the oxygen evolution reaction (OER)—due to the transfer of four protons and four electrons—has greatly hindered the commercial viability of water electrolysis. People have been committed to the development of alternative precious metal-free OER electrocatalysts, especially electrocatalysts for alkaline media. In this study, we report the application of Sr₆(Co_0.8Fe_0.2)₅O₁₅ (SCF-H) perovskite oxide with a hexagonal phase structure in the field of OER electrocatalysis. Synthesized by a simple and universal sol–gel method, the SCF-H perovskite oxide shows prominent OER activity with an overpotential of 318 mV at a current density of 10 mA cm⁻² and a Tafel slope of only 54 mV dec⁻¹, which is significantly better than the cubic phase structure SrCo_0.8Fe_0.2O_3−δ (SCF-C), benchmark noble-metal oxide RuO₂ and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF). Compared with cubic SCF-C, the hexagonal SCF-H perovskite oxide has abundant surface oxygen species (O₂²⁻/O⁻), a faster charge transfer rate, and a higher electrochemical surface area. In addition, the DFT calculation results show that the center of the O p-band of SCF-H is closer to the Fermi level than that of SCF-C, which leads to the better OER activity of SCF-H. This work finds that the new hexagonal structure perovskite may become a promising OER electrocatalyst.