Synthesis of atomically dispersed M—N—C catalysts via selective metalation
A method of making an M-N—C catalyst is disclosed. The method includes the steps of (a) contacting an N-doped carbon support with a basic solution that includes a metal salt, whereby the N-doped carbon support is metalated by the metal cation of the metal salt to form one or more chelated metal-nitrogen complexes (MN x species); and (b) subsequently contacting the metalated N-doped carbon support with an acid, whereby the one or more MN x species formed on the N-doped carbon support in step (a) remain intact while other species are removed. The resulting composition may be catalytically activated by heat treating the composition. The activated catalyst may be used to catalyze a wide range of chemical reactions.
1 . A method of making an M-N—C catalyst, the method comprising:
(a) contacting an N-doped carbon support comprising one or more macrocyclic N 4 sites with a basic solution, the basic solution comprising a metal salt and a base is selected from the group consisting of trialkyl amine, alkali acetate, and any combination thereof, at a temperature from 30° C. to 250° C., whereby the N-doped carbon support is metalated by the metal cation of the metal salt to form a metalated N-doped carbon support comprising one or more chelated metal-nitrogen complexes; and
(b) contacting the metalated N-doped carbon support with an acid at a temperature from 20° C. to 60° C., whereby the one or more chelated metal-nitrogen complexes formed on the N-doped carbon support in step (a) remain intact.
2 . The method of claim 1 , wherein contacting the metalated N-doped carbon support with the acid in step (b) removes metal cations that are unselectively deposited onto or electrostatically adsorbed to the surface of the N-doped carbon support.
3 . The method of claim 1 , wherein the metal salt comprises a basic anion.
4 . The method of claim 3 , wherein the basic anion is selected from the group consisting of acetate and chloride.
5 . The method of claim 1 , wherein step (a) occurs at a temperature that is lower than 150° C., and wherein the basic solution comprises a strong base.
6 . The method of claim 1 , wherein the metal cation is selected from the group consisting of a Ni 2+ , Cu 2+ , Zn 2+ , Cr 2+ , Mn 2+ , Co 2+ , Fe 2+ , Fe 3+ , and any combination thereof.
7 . The method of claim 1 , wherein the acid is acetic acid.
8 . The method of claim 1 , further comprising the step of:
(c) heat treating the metalated N-doped carbon support formed in step (b), whereby the metalated N-doped carbon support becomes an activated M-N—C catalyst.
9 . The method of claim 8 , wherein step (c) is performed by heating the metalated N-doped carbon support formed in step (b) to a temperature of above 500° C.
10 . The method of claim 1 , wherein the N-doped carbon support is a product of heat treating a precursor mixture comprising one or more of ZIF-8 metal organic framework (MOF), polyaniline (PANI), 1,10-phenanthroline (Phen), and melamine (Mel).
11 . The method of claim 1 , further comprising heat treating a precursor mixture comprising carbon and nitrogen, thereby producing the N-doped carbon support comprising one or more macrocyclic N 4 sites.
12 . The method of claim 1 , wherein the M-N—C catalyst has a metal loading of from 0.3 wt % to 15 wt %, based on the total weight of the M-N—C catalyst.