In situ Probing of Mn₂O₃ Activation toward Oxygen Electroreduction by the Laser-Induced Current Transient Technique

Abstract

Electrochemical transformation of Mn4+ into Mn3+ in the Mn2O3 bixbyite structure is believed to activate this oxygen reduction catalyst for O2 electrosorption. The actual mechanism, however, still remains to be revealed and elucidated. This earth-abundant Mn-based material, viz., Mn2O3-rod catalyst, was found to have similar activity to Pt/C (20%) in alkaline media. Intrigued by this observation, an in-depth analysis was performed by combining different electrochemical techniques, including the laser-induced current transient technique. Deeper insights into the structure of the electrical double layer and its properties were obtained by probing the electrode surface with a laser beam to record laser-induced current transients to estimate the potential of zero charge. The synthesized Mn2O3 was further found to be an efficient electrocatalyst alternative to Pt/C (20%), an expensive and limited noble-metal catalyst.

Prospects of Using the Laser‐Induced Temperature Jump Techniques for Characterisation of Electrochemical Systems

“…[11] Besides using noble metal electrodes for the laser-induced temperature jump measurements, the PZC of Mn 2 O 3 was also successfully investigated. [14] The PZC, which is closely related to the PME, was located at 1.09 V vs RHE, thus, supporting the notion that Mn 2 O 3 should catalyze the oxygen reduction reaction (ORR) well since the obtained PZC is quite close to the thermodynamic equilibrium potential of the ORR. This work demystified and further confirmed the reasons for the good ORR performance of Mn 2 O 3 in this kind of electrolytes.…”

“…It should be noted that the pH dependency of the PME varies for the same electrode material with different surface structures [11] . Besides using noble metal electrodes for the laser‐induced temperature jump measurements, the PZC of Mn 2 O 3 was also successfully investigated [14] . The PZC, which is closely related to the PME, was located at 1.09 V vs RHE, thus, supporting the notion that Mn 2 O 3 should catalyze the oxygen reduction reaction (ORR) well since the obtained PZC is quite close to the thermodynamic equilibrium potential of the ORR.…”

Selective Electrochemical Production of Hydrogen Peroxide from Reduction of Oxygen on Mesoporous Nitrogen Containing Carbon

“…[22,23] Cobalt and manganese based catalysts are the most extensively used transition metal-based catalysts for reducing oxygen electrochemically. [24][25][26][27] Despite of all the advantages, carbon-based catalysts are known to exhibit significant advantages over them. [28][29][30] They are sustainable and environmental friendly, contain large surface area, ordered structure, porosity, cost effectiveness, high conductivity, high abundance in earth and defects which provide enhanced activity.…”

Rich Surface Oxygen Vacancies of MnO2 for Enhancing Electrocatalytic Oxygen Reduction and Oxygen Evolution Reactions

“…Since the discovery of a cubane‐like Mn 3 O 4 Ca structure as active site in the natural oxygenic photosystem II (PS‐II), manganese oxides (MnO x ) as ORR and OER electrocatalysts have captured intensive attention due to their natural abundance, variety of crystallographic structures, low cost, and toxicity. [ 6,15-20 ] For example, manganese dioxide (MnO 2 ) can be formed in various crystal structures, such as α‐MnO 2 with 2 × 2 tunnels, γ‐MnO 2 with 1 × 2 tunnels, and β‐MnO 2 with 1 × 1 tunnels, which is a type of most commonly studied manganese oxides for supercapacitors and oxygen‐based electrochemical reactions. [ 6,15,18,21-25 ] More importantly, some manganese oxides exhibited considerable catalytic activity for both the ORR and OER, when with the noble metal catalysts, and had been identified as one of the most promising bifunctional candidates.…”