Observation of Active Sites for Oxygen Reduction Reaction on Nitrogen-doped Multilayer Graphene

TL;DR

This study identifies the main active sites for oxygen reduction on nitrogen-doped multilayer graphene by analyzing chemical composition changes before and after the reaction, revealing that carbon atoms near pyridinic nitrogen are crucial for catalysis.

Contribution

It introduces an experimental method to pinpoint active sites on nitrogen-doped graphene using X-ray photoelectron spectroscopy analysis before and after ORR.

Findings

OH(ads) remains on carbons near pyridinic nitrogen after ORR

High OH(ads) attachment correlates with high catalytic efficiency

Carbon atoms near pyridinic nitrogen are the main active sites

Abstract

Active sites and catalytic mechanism of nitrogen-doped graphene in oxygen reduction reaction (ORR) have been extensively studied but are still inconclusive, partly due to the lack of an experimental method that can detect the active sites. It is proposed in this report that the active sites on nitrogen-doped graphene can be determined via the examination of its chemical composition change before and after ORR. Synchrotron-based X-ray photoelectron spectroscopy analyses of three nitrogen-doped multilayer graphene samples reveal that oxygen reduction intermediate OH(ads) which should chemically attach to the active sites remains on the carbon atoms neighboring pyridinic nitrogen after ORR. In addition, a high amount of the OH(ads) attachment after ORR corresponds to a high catalytic efficiency and vice versa. These pinpoint that the carbon atoms close to pyridinic nitrogen are the main active sites among the different nitrogen doping configurations.