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-(CH₂)₃NMe₃)]I₂ 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...[ Read more ]

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-(CH₂)₃NMe₃)]I₂ 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 TEABF₄/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 BF₃.Et₂O 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 NH₄PF₆ (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](PF₆)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](PF₆)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)(PPh₃)₃ were investigated. RuHI(CO)(PPh₃)₃ 8.3 shows the fastest insertion rate, while no reactions were found for X = F, N₃, NCS, and CN. Steric effect between X-ligand and PPh₃ (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 D₂O. Reactions of the ligands with n-BuLi and RuHCl(CO)(PPh₃)₃ 8.1 gave RuH(C^NHC,N^indole)(CO)(PPh₃) complexes. RuHCl(CO)(PPh₃)₃ 8.1 is the most active catalyst. RuH(C^NHC-Pen,N^indole)(CO)(PPh₃) 9.7 is selective for the deuteration of terminal olefinic protons but has much lower reactivity.