TiN Boosting the Oxygen Reduction Performance of Fe–N–C through the Relay-Catalyzing Mechanism for Metal–Air Batteries

Metal-air batteries desire highly active, durable, and low-cost oxygen reduction catalysts to replace expensive platinum (Pt). The Fe-N-C catalyst is recognized as the most promising candidate for Pt; however, its durability is hindered by carbon corrosion, while activity is restricted due to limited oxygen for the reaction. Herein, TiN is creatively designed to be hybridized with Fe-N-C (TiN/Fe-N-C) to relieve carbon corrosion and absorb more oxygen when catalyzing oxygen reduction. The half-wave potential of TiN/Fe-N-C is 0.915 V vs reverse hydrogen electrode with 15 mV lost after 30,000 cycles accelerated durability test, higher than 0.893 V and 26 mV of Pt/C. The solid zinc-air battery of TiN/Fe-N-C achieves a peak power density of 238 mW/cm², 2100 cycle stability at 30 °C, and long-term durability of 1100 h under -20 °C, superior to 150 mW/cm² and 500 h (-20 °C) of Pt/C. Both calculations and experiments indicate that TiN has dual functions which not only relay abundant oxygen for the reaction but also strengthen the adsorption force for intermediates of carbon corrosion reaction, thus, enhancing the activity and durability of Fe-N-C. Therefore, the proposed relay catalytic strategy by TiN offers an efficient Fe-N-C catalyst for energy conversion devices.