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

Abstract 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.