TRIS-mediated molecular dual regulation of solvation and electrode interfaces for high-performance iron-chromium redox flow batteries

The commercialization of iron-chromium flow batteries (ICFBs) is hindered by sluggish Cr 3+ /Cr 2+ kinetics caused by Jahn-Teller and parasitic hydrogen evolution reaction (HER). In this work we propose a collaborative “dual-regulation” strategy leveraging the synergistic effects of -OH hydrophilicity and -NH 2 electronegativity to optimize the coordination environment and inhibit HER. Through theoretical screening, tris(hydroxymethyl)aminomethane (TRIS) was identified as the optimal additive due to its superior electrostatic potential and balanced steric profile. Spectroscopic, electrochemical, and theoretical analyses demonstrate that TRIS, with its multiple electronegative sites, can act as a structural node to reconstruct hydrogen-bond networks and immobilize water. Simultaneously, TRIS adsorbs onto the electrode surface, where its nucleophilic -NH 2 groups penetrate the chromium solvation shell to facilitate ion transport. Consequently, an ICFB with 20 mM TRIS achieved 83.30% energy efficiency at 140 mA/cm 2 . This work offers a scalable solution for high-performance stationary energy storage.