Photoelectrochemistry of Redox-Active Self-Assembled Monolayers Formed on n-Si/Au Nanoparticle Photoelectrodes.

Controlling the chemistry of the electrode-solution interface is critically important for applications in sensing, energy storage, corrosion prevention, molecular electronics, and surface patterning. While numerous methods of chemically modifying electrodes exist, self-assembled monolayers (SAMs) containing redox-active moieties are particularly important because they are easy to prepare, have well-defined interfaces, and can exhibit textbook photoelectrochemistry. Here, we investigate the photoelectrochemistry of redox-active SAMs on semiconductor/metal interfaces, where the SAM is attached to the metal site instead of the semiconductor. n-Si/Au photoelectrodes were fabricated using a benchtop electrodeposition procedure and subsequently modified by immersion in aqueous solutions of (ferrocenyl)hexanethiol and mercaptohexanol. We explored the relevant preparation conditions, finding that after optimization, we were able to obtain canonical cyclic voltammetry for a surface-bound redox molecule that could be turned on and off using light. We then characterized the optimized electrodes under varying illumination intensities, finding that the heterogeneous electron transfer kinetics improved under higher illumination intensities. These results lay the foundation for future studies of semiconductor/metal/molecule interfaces relevant to sensing and electrocatalysis.

Characterizing and understanding the photovoltage in n-Si/Au light-addressable electrochemical sensors.

Here, we characterize the photovoltage of n-Si/Au light-addressable electrodes (LAEs) over a range of solution potentials from ca. -1 to +1 V. We find that the n-Si/Au photoelectrodes show photovoltages consistent with a semiconductor/liquid junction in contrast to a buried junction, which opposes our previous understanding of how photovoltage originates in these sensors.

A sustainable approach to cathode delamination using a green solvent.

Designing an environment-friendly delamination process for an end-of-life (EoL) composite cathode is a crucial step in direct cathode recycling. In this study, the green solvent dimethyl isosorbide (DMI) is explored to extract cathode active materials (AMs) from the Al current collector via dissolving the polyvinylidene fluoride (PVDF) binder. Mechanistic insight suggests that binder removal from the Al substrate proceeds via reducing polymer interchain interaction through DMI penetrating into the PVDF crystalline region. Polymer-solvent interaction may increase via establishing hydrogen bond between PVDF and DMI, which facilitates binder removal. Analytical characterizations including 1H NMR, FTIR, XRD and SEM-EDS reveal that the molecular, micro, and crystal structures of the recovered cathode AMs, PVDF and Al foil are preserved. This finding is expected to provide a replacement for the toxic organic solvent N-methylpyrrolidone (NMP) and offers an effective, ecofriendly, and sustainable direct cathode recycling approach for spent Li-ion batteries.