Spin state engineered ZnxCo3−xO4 as an efficient oxygen evolution electrocatalyst

Abstract

Oxygen evolution is the key step in the oxidation of water in electrolyzers and photoelectrochemical cells for the production of hydrogen. Developing a non-precious metal oxide catalyst with good electrocatalytic activity for the oxygen evolution reaction (OER) is very challenging. In this work, nanostructured Zn_xCo_3−xO₄ has been shown as an efficient catalyst with a low overpotential for the OER in 0.1 M KOH solution. Substitution of Co²⁺ in the spinel oxide Co₃O₄ with Zn²⁺ creates a higher number of high-spin Co³⁺, which is found to be directly correlated with the OER activity of Zn_xCo_3−xO₄. Zn_0.8Co_2.2O₄ (x = 0.8) with the optimum amount of Co²⁺/Co³⁺ and high-spin Co³⁺ content showed a very low overpotential of ∼250 mV, at 10 mA cm⁻², with a turnover frequency of ∼3 × 10⁻³ s⁻¹ for the OER. The high Faradaic efficiency along with the stability of Zn_0.8Co_2.2O₄ and electrocatalytic activity comparable with that of precious metal oxides indicate that this composition is a promising catalyst for water oxidation.