Self-healing of active site in Co(OH)2/MXene electrocatalysts for hydrazine oxidation

The development of efficient hydrazine oxidation reaction (HzOR) catalysts is important for the construction of remarkable energy storage and conversion systems. However, after a period of electrochemical reaction, the active site of the catalyst will be irreversibly reduced or inactivated, and how to recover the active site is a major challenge. Here, we report 2D Co(OH)2/Ti3C2(OH)x MXene composites with rapid reconstruction and self-healing behaviors as efficient and stable electrocatalysts during HzOR process. Both experimental and theoretical results indicate that the introduction of Ti3C2(OH)x MXene can effectively reduce the dehydrogenation barrier of Co(OH)2, from 0.584 eV to 0.481 eV to form the real catalytic active center Co(OH)O. Subsequently, Co(OH)O/Ti3C2(OH)x MXene composites with metal-like conductivity not only present spontaneous adsorption capacity of N2H4, but also can modulated rate-determining step of dehydrogenation of *N2H4 to *N2H3 (0.54 eV) compared with Co(OH)O. Finally, the electrophilic oxygen of Co(OH)O/Ti3C2(OH)x can spontaneously obtain electrons and protons from N2H4, achieving the oxidation of N2H4 while reducing Co(OH)O to Co(OH)2, thus completing the self-healing of the efficient catalyst.