Electrostatic Interaction in Amino Protonated Chitosan-Metal Complex Anion Hydrogels: A Simple Approach to Porous Metal Carbides/N-Doped Carbon Aerogels for Energy Conversion.

In the face of the increasingly serious rapid depletion of fossil fuels, exploring alternative energy conversion technologies may be a promising choice to alleviate this crisis. Transition metal carbides (TMCs)/carbon composites are considered as prospective electrocatalysts due to their high catalytic activities and structural stability. In this work, we report the simple synthesis of TMCs/N-doping carbon aerogels (TMCs/NCAs, including Fe3C/NCA, Mo3C2/NCA, and Fe3C-Mo2C/NCA) for the oxygen reduction reaction (ORR) using protonated chitosan/metal complex anion-chelated aerogels. Among them, the Fe3C/NCA composite possesses efficient ORR activity (similar to Pt/C), and the Fe3C/NCA-assembled Zn-air battery exhibits high power densities of about 250 mW cm-2. The density functional theory calculation reveals that the presence of graphite-N, pyridine-N, and carbon defects in the carbon framework effectively reduces the free energy of ORR occurring in Fe3C. This work provides a simple and extensible strategy for the preparation of TMCs from chitosan, which is expected to be extended to other metal carbides.