Electrode-assisted Catalytic Water Oxidation and Related Electrochemical Reactions

2 Electrode-assisted Catalytic Water Oxidation and Related Electrochemical Reactions 

Electrochemical water splitting to o ygen (o ygen-evolution reaction, OER) and to hydrogen (hydrogen-evolution reaction, HER) is an excellent potential 

Ohsaka and coworkers initially reported the outstanding catalytic enhancement of OER of MnO,c nanorod modified platinum, gold and glassy carbon (GC) electrodes and evaluated the loading level of MnO (in the manganite phase, y-MnOOH) and the pH of the electrolyte for OER. The nanorods showed a maximum activity in basic medium and the 

Nakamura and coworkers studied the pH effect (13 pH 4) for water oxidation at S-MnOa modified electrode. It was suggested that the decreased activity under neutral or acidic conditions was due to the instability of manganese(m) at pH 9 that disproportionates to manganese(n) and manganese(iv). The presence of manganese(iii) on the 8-Mn02 surface was concluded to be essential to reduce the overpotential for water oxidation and resulted in the ojgrgen production at an onset potential close to the thermodynamic reversible potential of the four-electron oxidation of water, E(02/H20) = 0.76 V, at pH 

The reported work by Nocera and coworkers concerning the dissolution and redeposition of MnO to form self-healing stable electrocatalysts under acidic, neutral, and basic conditions not only supported that manganese(iii) underwent disproportionation in acidic medium, whereas the one-electron-one-proton PCET (proton-coupled electron transfer) pathway is dominant under alkaline conditions, but resulted in a Tafel slope of 60 mV dec in alkaline pH regime.Apart from the usually discussed overpotential of electrochemical water oxidation, the kinetics of the reaction has also been considered for an efficient electrocatalyst. It is well known that the higher the Tafel slope value, the higher the energy needed to reach maximum current density. 

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