Oxygen reduction reaction: Semi-empirical quantum mechanical and electrochemical study of Printex L6 carbon black

Amorphous carbon black (CB) is a highly reactive material for O₂ reduction and widely employed in H₂O₂ generation. Most studies published have confined their investigation to few electrochemical properties of CB and its morphological and structural characterization. However, an in-depth understanding of CB properties and their effects on oxygen reduction reaction appears to be the key to making significant progress in this field. This paper describes the use of quantum mechanical semi-empirical calculations to obtain structural information and electrochemical impedance spectroscopy to access the electrochemical information of Printex L6 CB (PCL6). It is the first report of its kind in the literature. The semi-empirical results show that PCL6 electrode presents an increase in the number of hotspots due to the presence of large amount of sp² carbon and functional groups in its composition, which favors O₂ adsorption at lower potentials. The equilibrium distance on PCL6 electrode is closer to the distance of a double bond (C[dbnd]O), reinforcing O₂ bridge-like adsorption model. Furthermore, PCL6 had proved to be thermodynamically more favourable to O₂ adsorption and requires relatively lower energy and potential (shift of 150 mV). PLC6 is found to undergo an activation process, probably associated with O₂ adsorption, prior to the beginning of reaction.