Nitrogen-Doped Metal-Free Carbon Materials Derived from Cellulose as Electrocatalysts for the Oxygen Reduction Reaction

Development of metal-free carbon-based electrocatalysts for reducing oxygen to water (ORR), preferentially following a 4 electron transfer pathway, is of high importance. We present a two-step synthesis of N-doped carbon-based ORR electrocatalysts by using an efficient thermal treatment of hydrothermally carbonized cellulose in ammonia combining devolatilization, reduction and nitrogen doping. The influence of the synthesis temperature as well as of the ammonia concentration used during the synthesis on the electrocatalytic ORR activity was analyzed using bulk- and surface-sensitive techniques. Correlation of electrocatalytic activity with structural features of the catalysts provided deeper mechanistic understanding and enabled us to optimize the synthesis conditions. The nitrogen-doped metal-free catalyst originating from the treatment in 100 % NH3 at 800 degrees C achieved a current density of -1 mA cm(-2) at 0.83 V vs. RHE positioning it among the most active noble-metal free and biomass-based ORR catalysts reported so far.