Redox‐Functionalized Semiconductor Interfaces for Photoelectrochemical Separations

Abstract

Redox‐mediated electrosorption is a promising platform for selective electrochemical (EC) separations, due to its molecular selectivity, high uptake, and tunability for target ions. However, the electrical energy required is mainly generated by non‐renewable energy sources, which limits its sustainability and overall impact to decarbonization. Here, a redox‐mediated photoelectrochemical (PEC) separation process using polyvinyl ferrocene functionalized TiO2 nanorod electrodes is proposed, which integrates direct solar energy as a driver for the selective electrosorption. The photoelectrochemically‐driven oxidation and reduction with both homogeneous and heterogeneous ferrocene‐systems is investigated to establish the underlying mechanism. The PEC system can separate heavy metal oxyanions at lower voltages or even without electrical energy. At 0.3 V versus SCE, a 124 mg g−1 uptake for Mo is achieved, which is comparable to the performance of EC cells at 0.75 V versus SCE. Thus, PEC systems not only can generate energy for spontaneous redox‐separations, but also can reduce electrical energy consumption by 51.4% compared to EC cells for separation processes when coupled with an external electrical energy.

Molecularly Selective Polymer Interfaces for Electrochemical Separations

“…As emphasized throughout this Perspective, engineering of the electrochemical systems is as important as tailoring the molecular interfaces for industrial implementation and for achieving economically feasible translation to practical use. From a systems perspective, the considerations include the number and assembly of the flow channels, optimization of the operating conditions (e.g., batch/continuous modes, parallel/series connections, and constant voltage/constant current operations), and the integration of greener energy sources (e.g., solar panels, waste-heat sources, ,,, and photoelectrochemistry , ). Life cycle assessment (LCA) and technoeconomic analysis (TEA) are also indispensable tools for assessing the feasibility of system designs toward practical translation.…”