Electrolytes Based on Nanoscale Organic-Inorganic Hybrid Materials (NOHMs)

Abstract

The potential use of nanoparticle organic hybrid materials (NOHM) as electrolytes in redox flow batteries is being explored. NOHMs are composite particles formed by polymers grafted (either ionically or covalently) onto surface-modified inorganic nanoparticles. Such structure has great potential to capture and carry nonpolar electroactive species.1 In this work, the protonation behavior, and the effect NOHM structures have on metal cation uptake is evaluated. Both NOHMs considered in this analysis comprise silica cores ionically grafted with polymer tails. The polymer tails correspond to polyethylimine for the NOHM-I-PEI, and to polyetheramine with a sulfonic acid linker for the NOHM-I-HPE. Cyclic voltammetry was used to investigate the interaction of the copper species as the concentration of the NOHM of interest increases (Figure 1). NOHM-I-PEI showed inhibition of the oxidation and reduction peaks as the NOHM concentration increased, suggesting the formation of the cuprammonium complex. The formation of this complex was also explored via acid-base titration and UV-Vis. On the other hand, the dynamics of neat and NOHM-based fluids was explored via NMR. DOSY was used to explore the diffusion coefficients of the pure polymers and the NOHMs.