High performance ORR electrocatalysts prepared via one-step pyrolysis of riboflavin

4 years ago

High performance ORR electrocatalysts prepared via one-step pyrolysis of riboflavin

Efficient, cost-effective electrocatalysts for an oxygen reduction reaction (ORR) are currently required for fuel cells. In the present work, riboflavin was used as a cheap, nontoxic carbon and nitrogen precursor to prepare Fe–N–C catalysts via one-step pyrolysis in the presence of anhydrous iron chloride. Raman spectroscopy indicated that the catalyst containing nitrogen created a great quantity of defects in the carbon structures, while nitrogen adsorption-desorption isotherms showed that the catalyst was mesoporous. Transmission electron microscopy demonstrated that the Fe–N–C catalyst was composed of very thin, curved and porous graphene layers together with some Fe2O3 nanoparticles, and X-ray diffraction patterns confirmed that the carbon in the catalyst was highly graphitized. X-ray photoelectron spectroscopy indicated that the active sites for the ORR were primarily composed of graphitic nitrogen, although Fe sites also played an important role. The ORR activity of the Fe–N–C catalyst reached a maximum of 4.16 mA cm⁻², and its chronoamperometric response was found to decrease by only 3% after operating for 3 h at 0.66 V (vs RHE) in an O2-saturated 0.1 mol L⁻¹ KOH solution. In contrast, a commercial 40 wt% Pt/C catalyst with a loading of 0.2 mgPt cm⁻² exhibited an activity of 4.46 mA cm⁻² and a 40% loss of response. The electrochemical performance of this new Fe–N–C catalyst was therefore comparable to that of the Pt/C catalyst while showing significantly better stability.

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DOI: S1872206717628857