Abstract
Electrochemical oxidation is becoming a promising technology for water remediation, as it holds numerous advantages, such as highly energy efficient and amenable to automation. The improvement in the electrochemical performance is often pursued through the addition of metal-based redox couples (e.g., Ce(III)/Ce(IV) and Co(II)/Co(III)) in the electrochemical systems, which generally requires the usage of acidic media and could potentially cause secondary pollution by releasing metal ions into the environment.
In this work, we demonstrate that hybrid electrodes, which are composed of metal oxides (i.e., indium tin oxide (ITO) and titanium dioxide (TiO2)) and the surface-bound Ru(II)poly(pyridyl) molecular complex, are able to not only reduce the risks of releasing heavy metal ions but also make full use of the Ru(II)/Ru(III) redox couple to achieve a four-fold improvement in reaction rate constant when compared with the pristine metal-oxide electrodes. Due to the significant and complicated interplay between the metal-oxide substrates and immobilized complex, variations are observed in both electronic structures and electrochemical responses, which creates opportunities for modulating the properties of the hybrid assemblies to obtain optimized electrochemical water remediation performance, including but not limited to suppressing water splitting (which is the competing side reaction for water remediation) and redirecting the oxidation mechanism from active hydroxyl radicals to highly oxidative Ru(III) in the immobilized complex.
Overall, this work provides a proof of concept that the intrinsic interplay between metal oxides and surface-bound molecular complex can be leveraged to achieve significantly enhanced electrochemical performance towards water remediation, as compared to the individual components.
References: Xiang He, Michael S. Eberhart, Alex B. F. Martinson, David M. Tiede, Karen L. Mulfort, Molecularly Functionalized Electrodes for Efficient Electrochemical Water Remediation, 2021, submitted.