Redox flow batteries (RFBs) have attracted considerable interest due to their potential for
large scale renewable energy storage applications. An aqueous bipolar organic salt [(bpy-(CH
2)
3NMe
3)]I
2 2.4 was developed as an anolyte, catholyte and charge carrier to mitigate cross-contamination
of electrolytes in RFBs. Such compound displays a high theoretical energy
density of 32.5 Wh L
-1 and superior stability with no chemical decomposition after 290 cycles.
We have synthesized and explored the electrochemical properties of dialkoxybenzene-based
and acylpyridinium-based combi-molecules. 2,5-dimethyl-1,4-dialkoxybenzene/viologen 3.21 displays a cell voltage of 1.83 V and a solubility of 0.66 M in
MeCN. Its symmetric RFB shows a capacity retention of 99.5 % within 35 cycles.
Benzoylpyridinium...[
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Redox flow batteries (RFBs) have attracted considerable interest due to their potential for
large scale renewable energy storage applications. An aqueous bipolar organic salt [(bpy-(CH
2)
3NMe
3)]I
2 2.4 was developed as an anolyte, catholyte and charge carrier to mitigate cross-contamination
of electrolytes in RFBs. Such compound displays a high theoretical energy
density of 32.5 Wh L
-1 and superior stability with no chemical decomposition after 290 cycles.
We have synthesized and explored the electrochemical properties of dialkoxybenzene-based
and acylpyridinium-based combi-molecules. 2,5-dimethyl-1,4-dialkoxybenzene/viologen 3.21 displays a cell voltage of 1.83 V and a solubility of 0.66 M in
MeCN. Its symmetric RFB shows a capacity retention of 99.5 % within 35 cycles.
Benzoylpyridinium iodide 4.5, ferrocene/acylpyridinium bipolar compound 4.6, and 1,4-dialkoxybenzene/acylpyridinium bipolar compound 4.12 were recognized as potential bipolar
candidates for RFBs.
Nitrobenzene and their derivatives were employed as anolyte candidates in non-aqueous
RFBs. Nitrobenzene 5.1 shows a low redox potential of -1.73 V and a high solubility of 6.5 M
in 0.5 M TEABF
4/MeCN. The 5.1/DBMMB RFB was successfully operated for more than 100
cycles, with a cell voltage of 2.20 V and a theoretical energy density of 192 Wh L
-1. Azobenzene
is a major decayed product for the nitrobenzene-based RFBs.
Reactions of 1,3-diketone (or 1,3-diimine) with BF
3.Et
2O produced the corresponding
boron-based compounds. The tert-butyl diketonate 6.6 shows a reversible redox at -1.83 V and
a high solubility of 2.0 M in MeCN. The 6.6/DBMMB RFB was operated for 100 cycles, with
a cell voltage of 2.57 V and a theoretical energy density of 69 Wh L
-1.
Two synthetic approaches were developed for the preparation of [M(tpy)
2]-like complexes
(M = Cr, Mn, Fe, Co, Ni, Cu, Zn). The first method is applicable to all those complexes except
Cr. One-pot reactions of tpy-ligand, metal salts, and NH
4PF
6 (or NaOTf or LiTFSI) generated
[M(tpy)
2]
2+. [Ni(tpy-4OMe)
2](TFSI)
2 7.25 exhibits a reversible redox at + 1.19 V and a
solubility of 0.61 M in MeCN. Its symmetric all-nickel RFB achieves a high cell voltage of 3.0
V and a theoretical energy density of 25 Wh L
-1. [Cr(tpy-2OMe)
2](PF
6)
2 7.2-Cr can be prepared
by another approach involving three-step synthesis via the formation of Cr(tpy)(OTf)
3 7.10.
[Cr(tpy-2OMe)
2](PF
6)
2 7.2-Cr displays three reversible redox peaks at negative potentials.
Such complex could be a potential multi-electron anolyte in RFB.
The X-ligand effects on alkyne insertion of RuHX(CO)(PPh
3)
3 were investigated.
RuHI(CO)(PPh
3)
3 8.3 shows the fastest insertion rate, while no reactions were found for X = F,
N
3, NCS, and CN. Steric effect between X-ligand and PPh
3 (trans to H) is a dominant factor to
determine the insertion rates when X = halides, while π-ability is more vital when X =
pseudohalides.
Several [C
NHC,N] ligands and their ruthenium hydride complexes were developed for H/D
exchange reactions of olefins with D
2O. Reactions of the ligands with n-BuLi and
RuHCl(CO)(PPh
3)
3 8.1 gave RuH(C
NHC,N
indole)(CO)(PPh
3) complexes. RuHCl(CO)(PPh
3)
3 8.1
is the most active catalyst. RuH(C
NHC-Pen,N
indole)(CO)(PPh
3) 9.7 is selective for the deuteration
of terminal olefinic protons but has much lower reactivity.
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