Structural study on Ti-ion complexes in concentrated aqueous electrolytes: Raman spectroscopy and high-energy X-ray total scattering

Tsurumura, Tatsuya; Ohkubo, Kota; Tanaka, Tomokazu; Fujii, K.

doi:10.1016/j.molliq.2020.112867

Cited by 3 publications

(8 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Extensive literature report (Lingane and Kennedy, 1956;Miyanaga et al, 1990;Kavan et al, 1993;Cservenyák et al, 1996;Sole, 1999;Bahdad, 2020;Tsurumura et al, 2020;Choe et al, 2021) the solvation behavior of Ti 4+ /Ti 3+ redox couple with different ligands in various acids solutions like H 2 SO 4 , HCl, HNO 3 and H 3 PO 4 . The redox stability of Ti 4+ /Ti 3+ is influenced by the formation of different reaction/intermediate complexes that appear in various acids as discussed below.…”

Section: Ti 4+ Complexes In Acidsmentioning

confidence: 99%

“…Thus, high pH conditions (typically with high SO 4 2concentrations and low H + concentration) are to be avoided when designing electrolytes for Ti RFBs. Upon electrochemical reduction of Ti 4+ to Ti 3+ , there occurs substantial change in the structures of Ti-ion complexes and nanoscale Ti 4+ aggregates are gradually disrupted to yield mononuclear Ti 3+ complexes (Tsurumura et al, 2020). The Ti 3+ ion is stable at very low pH (< ca 1.5) as seen through Pourbaix diagram.…”

Section: The H 2 So 4 Systemmentioning

confidence: 99%

See 1 more Smart Citation

Aqueous titanium redox flow batteries—State-of-the-art and future potential

2022

View full text Add to dashboard Cite

Market-driven deployment of inexpensive (but intermittent) renewable energy sources, such as wind and solar, in the electric power grid necessitates grid-stabilization through energy storage systems Redox flow batteries (RFBs), with their rated power and energy decoupled (resulting in a sub-linear scaling of cost), are an inexpensive solution for the efficient electrochemical storage of large amounts of electrical energy. Titanium-based RFBs, first developed by NASA in the 1970s, are an interesting albeit less examined chemistry and are the focus of the present review. Ti, constituting 0.6% of the Earth’s crust and an ingredient in inexpensive white paints, is amongst the few elements (V and Mn being some others) which exhibit multiple soluble oxidation states in aqueous electrolytes. Further, the very high (approaching 10 M) solubility of Ti in low pH solutions suggests the possibility of developing exceptionally high energy density aqueous Redox Flow Batteries systems. With these advantages in mind, we present the state-of the-art in Ti-RFBs with a focus on Ti/Mn, Ti/Fe and Ti/Ce couples and systems that use Ti as an additive (such as Ti/V/Mn). The inherent advantages of inexpensive Ti actives and relatively high energy density is contrasted with potential side-reactions resulting in reduced energy efficiency. Technological pathways are presented with a view to overcoming critical bottlenecks and a vision is presented for the future development of Ti-RFBs.

show abstract

Section: Ti 4+ Complexes In Acidsmentioning

confidence: 99%

Section: The H 2 So 4 Systemmentioning

confidence: 99%

Aqueous titanium redox flow batteries—State-of-the-art and future potential

2022

View full text Add to dashboard Cite

show abstract

“…In various acidic environments (i.e., H 2 SO 4 , HCl, HNO 3 , HClO 4 , H 3 PO 4 ), Ti ions display a diverse range of complex formations, influenced by both the specific acidic medium and their oxidation states. 3,[14][15][16][17][18][19][20][21] The reversibility of the Ti 4+ /Ti 3+ couple is significantly impacted by different acidic conditions and their concentrations. For instance, polarography experiments have revealed that the Ti 4+ /Ti 3+ couple demonstrates high reversibility in H 3 PO 4 , irrespective of acid concentration.…”

mentioning

confidence: 99%

“…Due to the absence of a 3d orbital, Ti 4+ (3d°) ion has a high charge-to-ionic radius ratio, preventing the formation of simply hydrated [Ti(H 2 O) 6 ] 4+ . 15 Furthermore, the existence of interactions involving Ti-O (where O is derived from H 2 O) has been predicted, along with interactions of Ti-O-Ti, and Ti-O-S. 17 It is anticipated that Ti 4+ exists in either mononuclear complexes (chelating complexes) or multinuclear complexes (bridging bidentate complexes) at higher SO 4 2− concentrations (and high pH values). 23 Mononuclear complexes, such as [Ti(OH) 2 SO 4 (H 2 O) 3 ]°, [Ti(OH) 2 (SO 4 ) 2 (H 2 O) 2 ] 2− , and [Ti=O(OH) 2 (H 2 O) 3 ]°, are formed through the coordination of Ti 4+ ions with SO 4 2− .…”

mentioning

confidence: 99%

“…15 Tsurumura et al have suggested that nanoscale aggregation is less pronounced in Ti 3+ solutions compared to Ti 4+ solutions, resulting in the absence of Ti-O-Ti-O-polymer structures in Ti 3+ , while they exist in Ti 4+ solutions. 17 Another study proposed that the maximum number of Ti 4+ polymer ions exist in solutions with a H 2 SO 4 concentration range of 1.4 M to 1.6 M. Further increases in H 2 SO 4 concentration lead to the breakage of polymer chains, forming monomeric Ti 4+ species, which dominate in H 2 SO 4 solutions with concentrations of 5 M to 8 M. 18,26 The presence of Ti 4+ ion is expected in the form of Ti 4+ , Ti(OH) 4 , Ti(OH) 3+ , Ti(OH) 2 2+ , TiH(OH) 2…”

mentioning

confidence: 99%

See 1 more Smart Citation

Low pH Titanium Electrochemistry in the Presence of Sulfuric Acid and its Implications for Redox Flow Battery Applications

Ahmed,

Sankarasubramanian

2024

J. Electrochem. Soc.

View full text Add to dashboard Cite

Titanium (Ti) is a promising elemental redox active species for redox flow batteries (RFBs) due to its 100x availability in the Earth crust, and 10x lower cost (compared to elemental vanadium). Furthermore, Ti salts are highly soluble in water and concentrations >5 M can be easily obtained. Seeking to harness the higher solubility (and hence energy density) of the Ti electrolyte for flow battery applications, the Ti4+/Ti3+ redox couple was investigated at high concentrations (up to 5 M) relevant to RFB applications. The behavior of Ti ions in H2SO4 supported electrolytes was investigated by varying the ratio of Ti redox active species to counterion. The electrochemical characteristics, transport properties, and redox kinetics of the Ti4+/Ti3+ redox couple were measured and the impact of the Tix+ to solvating ligand ratio was examined. The coordination structures around solvated Tix+ ions were spectroscopically determined and the effect of solvation structure on the Ti3+/Ti4+ redox rate constants were examined and correlated to the calculated solvation energy (hence distinguishing between inner- and outer-sphere processes) and the role of catalysts was addressed. The Ti electrolyte development guidelines presented herein will advance the development of Ti-based RFBs as a promising pathway towards cost effective, grid-scale energy storage.

show abstract

First-principles molecular dynamics simulation study on Ti4+ ion in aqueous sulfuric acid

et al. 2021

View full text Add to dashboard Cite

A first-principles molecular dynamics simulation study was carried out to investigate the structural features of Ti4+ in aqueous sulfuric acid. Ti4+ forms several stoichiometric compounds in aqueous sulfuric acid, the identity and structural information details of which have been the subject of numerous studies. Three stoichiometric compounds of Ti4+ in aqueous sulfuric acid were found in the simulations, namely, [Ti=O(OH)2(H2O)3], [Ti(OH)2(H2O)2SO4], and [Ti2O2(H2O)5(OH)2SO4]. The results indicated that HSO4− formed a complex with the Ti ion by releasing its proton, which implies that such a coordination increases the proton concentration in the solution. The multinuclear complex was formed in our simulation conditions (concentration: 1M Ti4+ and temperature: 353 K); the result supports the interpretation of a previous experimental study.

show abstract

Structural study on Ti-ion complexes in concentrated aqueous electrolytes: Raman spectroscopy and high-energy X-ray total scattering

Cited by 3 publications

References 32 publications

Aqueous titanium redox flow batteries—State-of-the-art and future potential

Aqueous titanium redox flow batteries—State-of-the-art and future potential

Low pH Titanium Electrochemistry in the Presence of Sulfuric Acid and its Implications for Redox Flow Battery Applications

First-principles molecular dynamics simulation study on Ti4+ ion in aqueous sulfuric acid

Contact Info

Product

Resources

About