Project description
Toward a unified and universal redox scale relevant for all solvents
Oxidation-reduction reactions, known as redox reactions, underly a plethora of applications among which are electrocatalysis and electrochemical energy storage. In these reactions, a transfer of electrons between two species results in the oxidation of one (loss of one or more electrons) and the reduction of the other (gain of one or more electrons). The electrochemical potential of the reactants is a measure used to predict the feasibility of a redox reaction. It is currently quantified on the basis of the specific solvent in which the reaction is to take place. The EU-funded InnoChem project will establish a unified redox scale to compare electrochemical potentials in all media.
Objective
The elementary steps underlying the reversible addition and removal of electrons from matter M –Metals, Molecules or Materials– are the fundament to describe redox chemistry, electrocatalysis and electrochemical energy storage. However, the electrochemical potentials of reaction partners are only comparable within one solvent. This is a consequence of the solvent specific standard states.
For this reason, it is a Grand Challenge to establish a Unified Redox Scale to compare electrochemical potentials in all media without extra-thermodynamic assumptions. To achieve this, we use an ‘ideal’ Ionic Liquid Salt Bridge setup to measure the Gibbs transfer energies between different solvents. The measured values, corrected for residual liquid junction potential contributions, will be used to directly connect potentials to the aqueous scale. This unifying solvent-independent scale will allow for knowledge-based comparison and selection of reagents for redox reactions in the next sections.
Reagents for deelectronation (removal of an e–) at high potential are scarcely available. Hence, we prepare perhalogenated radical cation salts that act as innocent Deelectronators (iD+) with high unified redox potentials. An iD+ converts a given neutral M to the ‘naked’ cation M+. iD+-salts are straightforwardly accessible and room-temperature stable materials. Conveniently, they are in part weighable in air. Combined with suitable non-reactive, weakly coordinating but polar innocent solvents and robust weakly coordinating anions, reactive cation salts are accessible.
Such reversible iD+-mediated redox-processes at high potential are appealing for electrosynthesis and -catalysis. To generate, study and apply these systems, we introduce a generally applicable innocent solvent family compatible with the high potential of iD+ and M+ – also with commercially available anions. Suitable iD+/solvent couples for targeted reactions are selected based on their position on the unified redox scale.
Fields of science
Programme(s)
- HORIZON.1.1 - European Research Council (ERC) Main Programme
Topic(s)
Funding Scheme
HORIZON-AG - HORIZON Action Grant Budget-BasedHost institution
79098 Freiburg
Germany