Rational fabrication of S-modified Fe–N–C nanosheet electrocatalysts for efficient and stable pH-universal oxygen reduction

Abstract

Constructing inexpensive, efficient, and stable pH-universal oxygen reduction electrocatalysts with controlled distribution of active species is of great importance for the exploration of green energy conversion devices. Herein, we demonstrated the rational preparation of S-modified Fe–N–C nanosheet catalysts with hierarchical porous architecture, large specific surface area (up to 1471 m2 g−1) and controlled S doping (up to 12.3 at.%) by the co-pyrolysis of cysteine, FeCl3 with Zn-mediated MgO template. Merited from rich and accessible active sites, the catalysts display outstanding oxygen reduction reaction (ORR) activity in terms of very small Ej3 (potential@3 mA cm−2, 0.87 V in 0.1 M KOH, 0.66 V in 0.1 M PBS (pH7.4) and 0.64 V in 0.5 M H2SO4) and overwhelming diffusion-limited current density (9.8, 6.1, 10.3 mA cm−2 in alkaline, neutral, acidic media, respectively), along with extremely respectable stability (∼90% activity retention for 53200, 26728, 43200 s in alkaline, neutral, acidic media, respectively), which underscore comparable or even better overall performance than commercial Pt/C and advanced pH-universal ORR catalysts ever reported. The as-assembled primary alkaline zinc–air battery delivers considerately large peak power density of 205 mW cm−2 and energy density up to 990.6 Wh kgZn−1 at 10 mA cm−2 (115 mW cm−2 and 676.7 Wh kgZn−1 for Pt/C-based battery), implying its highly promising application in practical energy conversion devices.