Fe—N—C catalysts synthesized by non-contact pyrolysis of gas phase iron
Me-N—C catalysts, wherein Me can include a transition metal, Mn, Fe, Co, or a combination of metals with Me-INU moieties located at the exterior surface of the Me-N—C catalysts are produced by a chemical vapor deposition synthesis. The synthesis methods can utilize non-solid-contact pyrolysis wherein a metal salt can be vaporized. Gaseous metal from the vaporized metal salt can displace a metal M from the N—C zeolitic imidazolate framework. The non-solid-contact pyrolysis does not mix solid iron precursors (e.g., Me═Mn, Fe, or Co) with the solid N—C zeolitic imidazolate framework precursors during or before the synthesis, which improves the process compared to conventional methods.
1 . An Fe—N—C catalyst comprising N—C sites and Fe atoms;
wherein at least 90% of the Fe atoms in the Fe—N—C catalyst are in Fe—N4 moieties;
wherein the ratio of Fe—N4 moieties located at an exterior surface of the Fe—N—C catalyst to the Fe—N4 moieties located within the Fe—N—C catalyst is about 100:1; and
wherein at least about 99% of the N—C sites at the exterior surface of the Fe—N—C catalyst are bound to Fe.
2 . The Fe—N—C catalyst of claim 1 , wherein the Fe—N—C catalyst comprises not less than about 2 weight % of Fe relative to the total weight of the Fe—N—C catalyst.
3 . The Fe—N—C catalyst of claim 1 , wherein at least about 99% of the Fe—N4 moieties are accessible by a gas-phase contacting the catalyst.
4 . The Fe—N—C catalyst of claim 1 , wherein the electrochemical surface area of the Fe—N—C catalyst is not less than about 1800 m 2 /g.
5 . The Fe—N—C catalyst of claim 1 , wherein the catalyst is capable of providing an IR-corrected current ≥33 mA/cm 2 at 0.90 V when used in a proton exchange membrane fuel cell.
6 . A cathode for a fuel cell comprising the catalyst of claim 1 .
7 . The cathode of claim 6 , wherein the fuel cell is a proton exchange membrane fuel cell.
8 . The cathode of claim 7 , wherein the proton exchange membrane fuel cell is capable of an oxygen reduction reaction activity of ≥44 mA/cm 2 at 0.89 VIR-corrected.