Improved Oxygen Reduction Activity of Transition Metal-Chelating Ordered Mesoporous Carbon Fuel Cell Catalysts by Milder Template Removal

Journal article, 2019

In the synthesis of iron-chelating ordered mesoporous nitrogen-functionalized carbon (Fe–OMC) catalysts, the removal of the silica template is a crucial and critical step. The silica removal method used today for the Fe–OMCs is based on the very toxic hydrofluoric acid (HF), which usage should be limited where possible. Therefore, the aim of this study is to establish a mild (user-friendly), yet efficient, etch method based on dilute sodium hydroxide (NaOH), which does not impair the catalytic performance of the catalyst, to replace the currently used HF method. A comparison between catalysts etched with HF versus NaOH was performed in order to gain understanding how the two etch methods influence the final catalysts in terms of electrochemical, structural and catalytic properties. The NaOH etch was found to successfully remove the silica template, and interestingly, also improve the catalytic performance. The improved activity is explained by a carbon activation process occurring in the catalyst treated with the NaOH etch. With these findings, we show that it is possible to remove the silica in a more user-friendly way and simultaneously increase the catalysts’ performance by activation of the carbon. Graphical Abstract: [Figure not available: see fulltext.].