Mixed-phase WO 3 Cocatalysts on Hierarchical Si-based Photocathode for Efficient Photoelectrochemical Li Extraction.

Photoelectrochemical lithium (Li) extraction can be expected to provide a useful recycle of Li + from waste Li-containing battery, but the process is limited by the photocathodes with poor Li + absorption and low yield rate. Here, we have designed a hierarchical silicon (Si)-based photocathode with mixed-phase tungsten oxide (WO 3 ) cocatalysts for photoelectrochemical Li extraction under 1 sun illumination, achieving a high Li yield rate of ≈223.0 μg cm -2  h -1 and an excellent faradaic efficiency of 91.9 % at 0.0817 V versus Li 0/+ redox couple. The WO 3 cocatalysts with the mixture of amorphous and crystalline phase accelerates the Li + insertion and precipitation and enriches the concentration of Li + at the photocathode surface. This robust photoelectrochemical Li extraction system provides a new insight on designing green and efficient route for cyclic utilization of Li resources in the sustainable energy field.