Electrochemical induction of Mn(III) in the structure of Mn(IV) oxide: Toward a new approach for water splitting

Oxygen-evolution reaction (OER) through water-oxidation reaction is an essential reaction for water splitting, which provides electrons for hydrogen production. Mn oxides are among the commonly investigated types of metal oxides as OER catalysts. Recent studies showed that Mn(III) ions in the structure of Mn(IV) oxide have an essential role in OER. Previous works have only focused on adding different materials to induce Mn(III) ions in the structure of Mn(IV). Indeed, Mn(III) ions could be induced in the Mn(IV)-oxide structure in the presence of organic compounds, reductants, fluoride, chloride, and gold nanoparticles. However, a challenging issue in the field is using a stable and perdurable force during OER to induce Mn(III) ions in the structure of Mn(IV). Herein, the effects of inducing Mn(III) ions on OER by different potentials on the surface of the prepared Mn(IV) oxide on fluorine-doped tin oxide were investigated in the phosphate buffer at pH 11, 7, and 3. Mn(IV) oxide under OER/Mn(III) induction shows no decrease in the current density, but for the same sample under OER alone, a decrease (15%) is observed in the current density after only 1000 s. At a lower inducing potential, a decrease for OER is observed, which corresponds to Mn(IV)/(III) reduction to Mn(II), and Mn(II) leaking effect. This investigation sheds new light on OER in the presence of Mn oxide and is a promising, low-cost, and environmentally friendly strategy, which results in an increase in the yield of OER.