Anti-corrosive Prussian blue film modified by polydopamine for energy extraction and sensing in seawater

Integration of a power supply and sensing parts by using Prussian blue (PB) film as a transit warehouse for electrons can be a potential solution for miniaturization of wireless ocean sensors. However, the by-product OH⁻ ions during operation can cause corrosion of the PB film, reducing the lifetime of the device. In this work, we modify PB films by coating a polydopamine layer which attaches tightly on the PB film through coordination bonding between the iron sites and the catechol groups. The polydopamine layer rejects OH⁻ ions, making the coated PB film anti-corrosive. Experiments demonstrate that electrons can transfer efficiently from a sacrificial metal electrode to dissolved oxygen molecules through the modified PB film. The external electric current can be used to light up a light emitting diode (LED) by immersing the system in seawater. The voltage of the electric current correlates with the salinity and temperature of seawater, suggesting that the system can work as a sensor as well.