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Abstract

The oxygen evolution reaction (OER) is one of the bottlenecks of electrochemical water splitting. Metal-free carbons from biomass are highly abundant and can be easily synthesized. Their low price, high conductivity and functionalization makes them promising materials. Herein, we report about free-standing carbon electrodes as electrocatalysts for the OER. In contrast to powder-based catalysts, free-standing electrodes not only avoid additives, but also facilitate post analysis and better reflect industrial conditions. Here, the performance of pure carbon electrodes is compared to those of N-functionalized ones. Utilizing several analytical techniques, the difference in performance can be rationalized by physical properties. Especially, the analysis of the gaseous products is shown to be of crucial importance. It reveals that N-doped carbons generate more oxygen and are more robust against carbon corrosion. This illustrates the importance of measuring selectivity especially for carbon electrocatalysts, as higher currents do not necessarily result in higher catalytic activity.