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ChemBioChem : a European journal of chemical biology (2020). doi:10.1002/cbic.202000681, Published by Wiley-VCH, Weinheim

International audience; Cobalt and nitrogen co-doped carbon (Co/N/C) catalysts prepared by pyrolysis are promising electrocatalysts for hydrogen evolution reaction (HER). Construction of Co−N$_x$ active sites is an important strategy for improving HER activity. We developed a method for thermally controlled construction of the Co−N$_x$ active sites by applying a bottom-up synthetic methodology using an N-doped graphene nanoribbon (N-GNR). Preorganized aromatic rings in the precursors assist graphitization during generation of N-GNR which has N2 sites that coordinate to a cobalt ion. Atomically dispersed Co−N$_x$ sites in the catalysts are observed by electron microscopy. Moreover, the amount of Co−N$_x$ sites increases up to 0.31 wt% as confirmed by XPS and elemental analysis. The Co/N/C catalyst prepared from the precisely designed precursor forming an N-GNR shows HER activity with a low overpotential of 258 mV (in 1.0 M HClO$_{4aq}$) and 311 mV (in 0.1 M HClO$_{4aq}$) at 10 mA·cm$^{−2}$, and with a long-term stability.

Fe/N/C single-atom catalysts containing Fe-N-x sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe-N-4 sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe-N-4 sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe-N-4 sites catalyzing ORR with a TOF value of 0.21 e site(-1) s(-1) at 0.8V vs. RHE. This indicates that the formation of Fe-N-4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor.

1995, 【要旨】