Effects of alkali metal cations on oxygen reduction on N-containing carbons viewed as the interplay between capacitive and electrocatalytic properties: Experiment and theory

Abstract

The development of new electrocatalysts for the oxygen reduction reaction (ORR) is crucial for the sustainable energy economy. Both fundamental understanding of surface processes under operating conditions and suitable ORR activity measurements are necessary to select the best electrocatalyst candidate. In the present study, to contribute to this matter, we show that both the nature of alkali metal cations (Li+, Na+ and K+), composing supporting aqueous hydroxide solution, as well as the potential sweep rate in rotating disk electrode voltammetry measurements, influence the results of measurements of ORR activities of N-containing nanocarbons. Based on density functional theory calculations, we concluded that the specific interactions of hydrated cations with oxygen functional groups are responsible for such behaviour, leading to a close interplay between the electrode double layer charging and the parallel Faradaic process on carbon surface. From a practical point of view, the presented results indicate that it is necessary to standardize carefully the ORR measurements on different carbon materials. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45014 and Grant no. OI172043]

Keywords

• carbon electrocatalyst
• ORR activity measurements
• catalyst selectivity
• double layer capacitance