Electrocatalytic activity in the oxygen evolution reaction of nitrogen-doped mesoporous carbon-supported cobalt oxide nanoparticles

Abstract

The effective use of the active phase is the primary goal of optimisation of the supported catalysts, and porous carbon supports are very effective carriers of electrocatalysts. Nitrogen doping of the graphitic structure of carbon is often used to improve its electric conductivity and introduce active centers for the catalytic reaction. In the oxygen evolution reaction (OER), an additional active phase should be deposited onto the carbon support to provide a relevant catalytic activity. This study investigated the effect of nitrogen doping of the mesoporous carbons and the impact of oxidation pretreatment towards electrocatalytic activity in OER. The carbons were obtained by a hard-template method from KIT-6 silica with sucrose and aniline as carbon precursors. Nitrogen atoms were introduced with aniline at 5-6 wt.%. We used low-temperature oxygen plasma to obtain different quantities and speciation of oxygen functional groups. Cobalt spinel, Co3O4, was deposited onto the nitrogen-doped carbons using a sonochemical deposition approach as an active phase. Catalytic performance was evaluated in a three-electrode setup's OER. The electrocatalytic properties of the supports were substantially enhanced by introducing nitrogen atoms into the carbon structure despite the decrease in the catalysts' surface area. The OER overpotential decreased from 520 mV@10 mAcm-2 for carbon-only support to 410-420 mV@10 mAcm-2 for the nitrogen-doped materials. A further increase in the OER activity was observed upon cobalt doping, and the most active, nitrogen-doped carbon-supported catalyst exhibited an overpotential of 360 mV@10 mAcm-2. While nitrogen doping positively impacts the activity of the Co3O4@C, additional gains can be achieved by controlled surface oxidation of the carbon support. Finally, this research backs up the hypothesis that the presence of COO-type groups on the carbon support can boost the oxygen evolution activity of the cobalt phase. This provides valuable information for improving deposition methods and understanding how different catalyst components interact to enhance overall performance.