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 cathode comprising a perovskite oxide having 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
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 cathode of claim 1 , wherein M is Fe.
3. The cathode of claim 1 , wherein the weight ratio of perovskite oxide to nitride compound is from 10:1 to 1:10.
4. A solid oxide electrolyte cell comprising:
(a) the cathode of claim 1 ;
(b) an anode; and
(c) an electrolyte disposed between the cathode and anode;
wherein the cathode and anode are in electrical communication with a power supply configured to provide a voltage potential between the cathode and anode.
5. The cell of claim 4 , wherein the electrolyte is an oxygen-ion conducting solid electrolyte.
6. The cell of claim 4 , wherein the electrolyte comprises yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), gadolinium doped ceria (GDC), perovskite-type oxides such as lanthanum strontium gallium magnesium oxide (LSGM), lanthanum yttrium germanate (LaYGe), or a combination thereof.
7. The cell of claim 4 , wherein the anode comprises a combination of a lanthanum strontium manganate-type perovskite and at least one doped fluorite oxide, for instance yttria stabilized zirconia, GDC, and ABO 3 -type perovskite oxides where A is selected from alkaline earth metals and lanthanoids and B is one or more transition metals.
8. The cell of claim 4 , wherein the anode comprises palladium, platinum, silver, gold, yttria stabilized zirconia, lanthanum strontium manganate, or a combination thereof.