Solvent-free assembly of Co/Fe-containing MOFs derived N-doped mesoporous carbon nanosheets for ORR and HER

The difficulties in integration of different active sites and structural optimization are huge obstacles in developing multi-functional electrocatalysts. In the present work, a molten salt-assisted solid state assembly strategy is developed to prepare Fe/Co Zn MOFs composites. Subsequent carbonization of these MOFs yields Fe/Co decorated nitrogen doped mesoporous carbon (Fe/CoNCs). The obtained NCs possess several merits, such as i, Sheet-like structure with high porosity and tubular large mesopores (15 nm); ii, N-doped carbon skeleton; iii, Highly dispersed Fe/Co nanoparticles. Benefit from these structural superiority and the synergy between active sites, Fe/Co-NC showed high activity toward both ORR and HER. Among those, the Fe-NC showed excellent ORR activity, experienced four-electron ORR process showing high onset potential (0.963 V), half-wave potential (0.877 V vs. RHE) and outstanding durability (95% current retention after 20000 s). The Co-NC showed high HER activity, achieving a current density of 10 mA cm−3 with low over potential of 242 mV. The remarkable ORR and HER performance can be mainly attributed to the simultaneous incorporation of multi active centers, i.e. nitrogen moieties and metal species (Fe/Co) to synergistically boost the ORR and HER process, and high porosity to accelerate mass and electron transfer.