A hierarchically ordered porous Fe, N, S tri-doped carbon electrocatalyst with densely accessible Fe-Nx active sites and uniform sulfur-doping for efficient oxygen reduction reaction

Doping Fe N C catalysts with heteroatoms has been widely recognized as a most promising way to improve the electrocatalytic activity to achieve the replacement of Pt-based electrocatalysts for efficient oxygen reduction reaction (ORR). However, it is still a challenge to combine delicate control of the catalyst structure with heteroatom-doping to achieve optimal electrocatalytic efficiency. Herein, a strategy of combining chemical vapor deposition (CVD) with dual-template cooperative pyrolysis was rationally designed to synthesize the novel electrocatalyst with densely isolated single Fe atoms scattered on hierarchically ordered porous N and S codoped carbon (ISA-Fe/HOPNSC). The three-dimensional hierarchically ordered interconnected macro/mesoporous structure and uniform sulfur-doping make ISA-Fe/HOPNSC exhibit superb ORR performance in both alkaline and acidic electrolytes with a positive half-wave potential (0.920 V in 0.1 M KOH and 0.795 V in 0.5 M H 2 SO 4 ) as well as outstanding methanol tolerance and long-time stability. As cathode catalyst in Zn-air battery, ISA-Fe/HOPNSC also provides much better maximum power density (210.7 mW cm −2 ) and specific capacity (796.7 mAh g Zn −1 ) than those of Pt/C (112.6 mW cm −2 and 712.6 mAh g Zn −1 ). Remarkably, the synthesis strategy in this work proposes myriad opportunities for combining delicate control of the catalyst structure with heteroatom doping to synthesize high-performance ORR catalysts.