Materials for ammonia synthesis
Disclosed herein are doped perovskite oxides. The doped perovskite oxides may be used as a cathode material in an electrochemical cell to electrochemically generate ammonia from N 2 . The doped perovskite oxides may be combined with nitride compounds, for instance iron nitride, to further increase the efficiency of the ammonia production.
1. A method of generating ammonia, comprising:
electrochemically reducing H 2 O and N 2 with a composition comprising a perovskite oxide, to provide NH 3 and O 2 - ; and
oxidizing the O 2 1 to give oxygen gas,
wherein the perovskite oxide has the formula:
A 1 w A 2 x X y Fe z O 3 ,
wherein:
A 1 is selected from La, Tb, Gd, Sm, Pr, and Nd;
A 2 is selected from Sr, Mg, Ca, and Ba;
X is one or more metals in the +1 or +2 oxidation state;
w is from 0.5-1.0;
x is from 0-0.5;
y is from 0-0.5; and
z is from 0.5 to less than 1.0;
wherein w, x, y, and z are chosen to maintain electroneutrality, and
wherein w, x, y, and z are chosen to maintain electroneutrality, and wherein the composition further comprises one or more nitride compounds having the formula M a N b , wherein M is selected from Fe, Mb, Co, Cr, and V, a is selected from 1, 2, 3, or and 4, and b is selected from 1, 2, 3, and 4.
2. The method of claim 1 , wherein the electrochemical reduction is performed by supplying an electric current to the perovskite oxide of claim 1 , wherein the current applied is in an amount from 0.1-50 mA.
3. The method of claim 1 , wherein X is Ni, Co, Ti, Mn, Zn, Cu, Li, Al, Sc, V, Cr, Ga, Ge, Y, Zr, Nb, In, V, W, Mb, Pd, Pt, Ag, Au, Cd, or a combination thereof.
4. The method of claim 1 , wherein A 1 is La.
5. The method of claim 1 , wherein A 2 is Sr.
6. The method of claim 1 , wherein w is from 0.6 to 0.9.
7. The method of claim 1 , wherein z is from 0.6 to 0.9.
8. The method of claim 1 , wherein X is Ni or Co.
9. The method of claim 1 , wherein x is from 0.15 to 0.25.
10. The method of claim 1 , wherein y is from 0.15 to 0.25.
11. The method of claim 1 , wherein M is Fe.
12. The method of claim 1 , wherein the weight ratio of perovskite oxide to nitride compound is from 10:1 to 1:10.