Insight into the effect of intercalated alkaline cations of layered manganese oxides on the oxygen reduction reaction and oxygen evolution reaction

Abstract

The effect of the intercalated alkaline cations between the adjacent layers of multilayered manganese oxide (MnO) towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was investigated. Li-MnO, Na-MnO, K-MnO, Rb-MnO, and Cs-MnO provide OER overpotentials of 1.64, 1.70, 1.79, 1.83, and 1.84 V vs. RHE, respectively as well as ORR overpotentials of 0.71, 1.06, 1.13, 1.15, and 1.14 V vs. RHE, respectively. Li-MnO shows the highest bifunctional catalytic activity towards both the ORR and OER. In addition, the Gibbs free energy change of *OH adsorption is found to be the largest throughout the reaction pathways determining the rate of the whole ORR and OER.

2D Layered Manganese Oxide Nanosheets as a Bifunctional Electrocatalyst for Zn-Air Batteries

“…(25-31) δ-MnO 2 or birnessite-type layered manganese oxide, the 2D layers of edgesharing manganese octahedra (MnO6) with cations and/or water molecules intercalated within MnO2 layer, is an attractive structure because the valence states of the birnessite contain Mn (III) and Mn (IV) leading to a high catalytic activities and the structure is tunable of intercalated cations between MnO2 layers. (15,32,33) Here, we demonstrate Zn-air battery using K-birnessite as a bifunctional electrocatalyst with an open circuit potential (OCP) of 1.31 V versus Zn/Zn 2+ . Zn-air battery using K-birnessite exhibits a small potential gap between discharge and charge potential of 0.79 V along with high cyclability than the state-of-art mixed catalyst of Pt/C and RuO2.…”

“…(3,4) Zn-air battery is one of interesting energy storage devices due to their inexpensive cost, environmental friendliness, and safety which can generate energy via redox reaction between oxygen gas from the atmosphere at the air cathode and Zn metal at the anode. (5)(6)(7)(8)(9) Oxygen gas from the atmosphere diffuses through gas diffusion layer (GDL) and is reduced to form hydroxide anion (OH -; O2+H2O+4e -→ 4OH -) during discharge process which is known as oxygen reduction reaction (ORR) (9)(10)(11), while Zn metal at the anode is oxidized to form Zn 2+ (Zn → Zn 2+ + 2e -) and then reacted with OHto generate zincate intermediate (Zn(OH)4 2-; Zn 2+ + 4OH -→ Zn(OH)4 2-). (4,12,13) The zincate species is then transformed to zinc oxide (ZnO) and regenerated H2O and OH -(Zn(OH)4 2-→ ZnO + H2O + 2OH -).…”

“…(4,12,13) The zincate species is then transformed to zinc oxide (ZnO) and regenerated H2O and OH -(Zn(OH)4 2-→ ZnO + H2O + 2OH -). (4,12,13) During the charging process, OHis oxidized to regenerated oxygen gas (4OH -→ O2 + 2H2O + 4e -) which is known as oxygen evolution reaction (OER) (11,14). Therefore, the overall reaction of Zn-air battery is 2Zn + O2 → 2ZnO (E o = +1.65 V versus Zn/Zn 2+ ).…”

“…(4,12,13) Although metal-air batteries are a promising energy storage device, the sluggish kinetics of the ORR and OER is a major challenge of this battery which limits their practical applications. (15)(16)(17)(18) Hence, bifunctional electrocatalyst is the key factor to accelerate the rate of these reactions. (11,14,19) Platinum has been recognized as the superior catalyst for the ORR and ruthenium and iridium-based catalyst have been suggested as high-performance catalysts for the OER, however, expensive cost and low stability of these materials suppress their practical utilization.…”

“…(15)(16)(17)(18) Hence, bifunctional electrocatalyst is the key factor to accelerate the rate of these reactions. (11,14,19) Platinum has been recognized as the superior catalyst for the ORR and ruthenium and iridium-based catalyst have been suggested as high-performance catalysts for the OER, however, expensive cost and low stability of these materials suppress their practical utilization. (20)(21)(22)(23)(24) Manganese-based material is one of attractive candidates in alkaline-based electrolyte due to their natural abundance and low toxicity.…”