Gel-limiting strategy for large-scale fabrication of Fe-N-C single-atom ORR catalysts

Although transition metal single atom site catalysts (SASCs) show great potential in electrocatalysis, their large-scale controllable and flexible preparation remains a great challenge. In this article, we report a simple gel-limiting strategy for fabricating Fe-N-C single-atom catalysts and evaluate its feasibility in large-scale application. Results show that the production of Fe-SASCs can be controlled by the limiting immobilization of the hydroxyl-rich temperature-controlled gel combined with simple centrifugal treatment, even if the amount of Fe-feeding fluctuates within a certain range. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of Fe-N single-atom sites and uniform distribution of Fe on commercial activated carbon. As an ORR electrocatalyst, the Fe-SASC delivered a higher limiting diffusion current, more positive onset potential and half-wave potential (Eonset = 1.00 V, E1/2 = 0.87 V), and excellent methanol resistance than those of commercial Pt/C (Eonset = 0.97 V, E1/2 = 0.85 V). Using the prepared Fe-SASCs, a homemade Zn-air battery was assembled and demonstrated a higher open circuit voltage, power density, and stability, further proving the practical application value of our proposed method and as-prepared catalyst. More importantly, our reported strategy can be further developed and extended to the future preparation of more transition metal SASCs.