Single Fe atoms anchored by short-range ordered nanographene boost oxygen reduction reaction in acidic media

The development of efficient and stable single-atom electrocatalysts with earth-abundant metals have emerged as a promising alternative to the costly Pt-based nanomaterials for oxygen reduction reaction (ORR). Herein, we synthesize a highly efficient electrocatalyst with single Fe atoms anchored by N-doped short-range ordered carbon loading on 2 D reduced graphene oxide (RGO). Unlike the highly graphitized carbon materials in previous ORR catalysts, in which the diffusion of oxygen molecules (∼3.46 Å) are blocked by long carbon chains and small interlayer spacing (∼3.4 Å), it is found that the Fe/N-doped nanographene possesses large interlayer spacing (>4 Å) and short carbon fragments in one layer. The unique nanographene structure in nanoscale can facilitate the transport of oxygen molecules to the active sites of atomically dispersed FeN₄ and FeN₅. In acidic media for ORR, as-prepared Fe₁-N-NG/RGO catalyst exhibited half-wave potential (E_1/2) of 0.84 V versus the reversible hydrogen electrode, and the loss of E_1/2 is less than 5 mV during 15,000 potential cycles.