Mn-doped CoO for acid, neutral and alkaline electrocatalytic oxygen evolution reaction.

This work reports the application of Mn-doped CoO oxides in the electrocatalytic oxygen evolution reaction (OER). The materials were characterized by structural, morphological, and electrochemical techniques. The oxides with higher Co : Mn molar ratio presented a lower electron transfer resistance, and consequently the most promising OER activities. Pure CoO shows an overpotential at = 10 mA cm of 761, 490, and 240 mV, at pH 1, 7, and 14, respectively, and a high TOF of 1.01 × 10 s at pH 14. Tafel slopes around 120 mV dec at acidic pH and around 60 mV dec at alkaline pH indicate different OER mechanisms. High stability for CoO was achieved for up to 15 h in all pHs, and no change in the structure and morphology after the electrocatalysis was observed. The reported excellent OER activity of the Mn-Co oxides in a wide pH range is important to broaden the practical applicability in different electrolyte solutions.