Electrochemistry of Nanoscale Hybrid Materials (NOHM) Complexes

Abstract

Nanoparticle organic hybrid materials, also known as NOHMs, are composite particles formed by polymers grafted (either ionically or covalently) onto surface-modified inorganic nanoparticles. The unique structure and liquid-like properties of such material have promoted the interest on its application as an electrolyte with the potential to capture and carry nonpolar electroactive species.In this work two types of NOHMs are considered. Both systems 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 NOHM-I-PEI and NOHM-HPE with copper. NOHM-I-PEI showed a significant pH influence, with peak inhibition occurring at high pH. The protonation behavior of PEI and NOHM-I-PEI was explored (Figure 1). CV results suggest a strong binding of the copper ions and a potential competition between protons and metal ions. Copper hydroxide formation can also occur at higher pH. In contrast, onset potential shift was observed in presence of NOHM-I-HPE.These studies are complemented by exploration through Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). Through EPR, the nature of the ion in solution can be explored. On the other hand, 13C T1 relaxation of the NOHM-based electrolyte at different compositions provide information on the dynamics of the grafted polymers in solution Figure 1