Molten Salts Etching Driven In-Situ Construction of MOF-Derived Co/Co–N–C/MXene toward Oxygen Reduction Catalysis

The oxygen reduction reaction (ORR) is a critical reaction in many renewable energy conversion and storage systems, such as fuel cells and metal-air batteries. High price, poor stability, and scarcity of Pt-based electrocatalysts, which are commonly used for ORR, limit the development of fuel cells and metal-air batteries. Transition-metal and nitrogen codoped carbons (M–N–C) are deemed as promising alternative electrocatalysts for ORR. Nevertheless, achieving sufficient ORR activity with M–N–C still faces great challenges. Here, cobalt (Co)-decorated Co–N–C coupled with MXene (Co/Co–N–C@MS-MXene) catalysts are successfully prepared via an in-situ construction of ZIF-derived Co–N–C at the surface of MXene etched by a Lewis acid molten salt. The as-synthesized Co/Co–N–C@MS-MXene delivers a superior ORR catalytic activity with a half-wave potential of 0.75 V vs RHE and a diffusion-limiting current density of 5.1 mA cm–2. A 4-electron transferring process and high stability are enabled. The excellent ORR performance can be attributed to the highly active Co-decorated Co–N–C and strong electronic coupling of Ti–O–Co between Co–N–C and MS-MXene, which promote the catalytic kinetics of ORR. This work demonstrates a universal, efficient, and green approach for the in-situ construction of active sites on MXene substrates.