CrN supported by carbon nanosheets as efficient catalysts toward oxygen reduction reaction and Zn-air batteries

Exploring non-precious efficient oxygen reduction reaction (ORR) catalysts is of great significance to fuel cells and Zn-air batteries (ZABs). CrN is a theoretically promising ORR catalyst, but its potential needs to be unlocked by proper supports that provide high conductivity and high exposure of active sites. In this work, we introduce a novel synthesis of carbon nanosheets-supported CrN nanoparticles (CrN/C) by annealing the mixture of CrCl₃, 1, 10-phenanthroline and melamine via a two-step pyrolysis. The prepared CrN/C materials show good ORR activity and stability in acidic and alkaline media. The optimal CrN/C material has an ORR half-wave potential of 0.73 and 0.72 V (vs. reversible hydrogen electrode) in acidic and alkaline media, respectively. And it retains 82% and 78% of ORR current density in acidic and alkaline media after durability tests, respectively. Furthermore, the optimal CrN/C material-based self-breathing ZABs deliver a maximum power density of 168 mW·cm⁻², which is one of the highest among transition metal nitrides-based ZABs. It is found that the ORR activity of CrN/C materials is highly related to the Cr–N valence state. This work highlights the good potential of CrN as robust ORR catalyst and verifies its promising application in ZABs.