Mn-doped Co 3 O 4 for acid, neutral and alkaline electrocatalytic oxygen evolution reaction

This work reports the application of Mn-doped Co O 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 Co O 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 Co O 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.