Fluorenone/fluorenol derivatives for aqueous redox flow batteries
Aqueous electrolytes comprising fluorenone/fluorenol derivatives are disclosed. The electrolyte may be an anolyte for an aqueous redox flow battery. In some embodiments, the compound, or salt thereof, has a structure according to any one of formulas I-III where Q 1 -Q 4 independently are CH, C(R 1 ) or N, wherein 0, 1, or 2 of Q 1 -Q 4 are N; Q 5 -Q 8 independently are CH, C(R 2 ), or N, wherein 0, 1, or 2 of Q 5 -Q 8 are N; Y is C═O or C(H)OH; R 1 and R 2 independently are an electron withdrawing group; n is an integer >1; and x and y independently are 0, 1, 2, 3, or 4, where at least one of x and y is not 0.
1. An aqueous composition comprising:
an aqueous anolyte comprising
(i) a compound or a salt thereof having a structure according to any one of formulas I-III
where Q 1 -Q 4 independently are CH, C(R 1 ) or N, wherein 0, 1, or 2 of Q 1 -Q 4 are N,
Q 5 -Q 8 independently are CH, C(R 2 ), or N, wherein 0, 1, or 2 of Q 5 -Q 8 are N,
Y is C═O or C(H)OH,
each R 1 and R 2 independently is an electron withdrawing group,
n is an integer >1, and
x and y independently are 0, 1, 2, 3, or 4, where if none of Q 1 -Q 8 is N, then x and y are not 0, and
(a) R 1 and R 2 are different electron withdrawing groups, or
(b) the compound comprises two different R 1 or two different R 2 groups, or
(c) both (a) and (b);
(ii) a base; and
(iii) water.
2. The aqueous composition of claim 1 , wherein the compound is not 7-nitro-9-oxo-9H-fluorene-2-carboxylic acid, 7-nitro-9-oxo-9H-fluorene-4-carboxylic acid, 5-nitro-9-oxo-9H-fluorene-4-carboxylic acid, 7-amino-9-oxo-9H-fluorene-2-carboxylic acid, 7-amino-9-oxo-9H-fluorene-1-carboxylic acid, or 7-foramido-9-oxo-9H-fluorene-2-carboxylic acid.
3. The aqueous composition of claim 1 , wherein each R 1 and R 2 independently is —SO 3 Z, —CO 2 Z, —(CH 2 ) m PO 3 Z 2 , X, —NR′ 3 + , —NO 2 , —SO 2 R′, —CN, —CX 3 , —COX, —C(H)O, —C(O)R′, —C(O)NH 2 , —C(O)NHR′, —C(O)NR′ 2 , N═O, —OR′, or —(CH 2 CH 2 O) p R′, where
each R′ independently is H, substituted or unsubstituted aliphatic, or substituted or unsubstituted heteroaliphatic,
X is halo,
each Z independently is a counterion with a +1 charge;
m is an integer from 0 to 10; and
p is an integer from 1 to 10.
4. The aqueous composition of claim 1 , wherein each R 1 and R 2 independently is —SO 3 Z, —CO 2 Z, —CF 3 , —NO 2 , —CN, or —OH.
5. The aqueous composition of claim 1 , wherein the compound has a structure according to any one of formulas IA-IC, IIA-IIB, or IIIA-IIIC:
6. The aqueous composition of claim 5 , where the compound has a structure according to any one of formulas IB, IC, IIB, IIIB, or IIIC, and R 1 and R 2 independently are —CN, —OH, —SO 3 Z, —COOZ, —(CH 2 ) m PO 3 Z 2 , —CF 3 , —F, —Br, —NO 2 , or —(CH 2 CH 2 O) p R′.
7. The aqueous composition of claim 5 where the compound has a structure according to any one of formulas IA, IIA, or IIIA, and R 1 and R 2 independently are —SO 3 Z or —CO 2 Z.
8. The aqueous composition of claim 7 , wherein:
(i) x is 1 or 2, and each R 1 independently is —SO 3 Z or —CO 2 Z; or
(ii) y is 1, and R 2 is —SO 3 Z; or
(iii) both (i) and (ii).
9. The aqueous composition of claim 5 , wherein the compound has a structure according to formula IC or IIIC, where x is 2 and one R 1 is —OH.
10. The aqueous composition of claim 1 , wherein
R 1 and R 2 are asymmetrically positioned on the compound.
11. The aqueous composition of claim 1 , wherein the compound comprises
or any combination thereof.
12. The aqueous composition of claim 1 , wherein:
(i) the base comprises an alkali metal hydroxide; or
(ii) the compound has a concentration within a range of from 0.5 M to 1.5 M; or
(iii) both (i) and (ii).
13. The aqueous composition of claim 1 , consisting essentially of:
the base;
the compound; and
water.
14. An aqueous electrolyte system for a redox flow battery system, comprising:
an aqueous anolyte according to claim 1 ; and
an aqueous catholyte comprising water and an electrochemically active material.
15. The aqueous electrolyte system of claim 14 , wherein the aqueous catholyte comprises:
K 4 Fe(CN) 6 , K 3 Fe(CN) 6 , or a combination thereof; and
water.
16. The aqueous electrolyte system of claim 14 , wherein:
the aqueous anolyte comprises an alkali metal hydroxide and
or any combination thereof, where each Z independently is a counterion with a +1 charge; and
the aqueous catholyte comprises an alkali metal hydroxide and K 4 Fe(CN) 6 , K 3 Fe(CN) 6 , or a combination thereof.
17. A redox flow battery system, comprising:
the aqueous electrolyte system of claim 15 ; and
a separator.
18. The redox flow battery system of claim 17 , further comprising a carbon-based anode and a carbon-based cathode.
19. A compound or a salt thereof having a structure according to:
(i) any one of formulas IA-IIIA
where Y is C═O or C(H)OH, each R 1 independently is SO 3 Z or CO 2 Z, each R 2 independently is SO 3 Z or CF 3 , each Z independently is a counterion with a +1 charge, n is an integer greater than 1, and x and y independently are 1, 2, 3, or 4, wherein (a) R 1 and R 2 are different electron withdrawing groups, or (b) the compound comprises two different R 1 or two different R 2 groups, or (c) both (a) and (b); or
(ii) formula IC or formula IIIC
where Y is C═O or C(H)OH, x is 2, y is 0, and each R 1 independently is —CN or —OH.
20. A compound, comprising
wherein:
Y is C═O or C(H)OH; and
each Z independently is a counterion with a +1 charge.
21. A method for producing electrical energy, comprising:
pairing an aqueous solution comprising a compound according to claim 19 or a salt thereof wherein Y is C(H)OH against an oxidizing catholyte mixture in an electrochemical cell, thereby oxidizing the compound to its corresponding ketone where Y is C═O and producing electrical energy.