Ion Sputtering–Assisted Double‐Side Interfacial Engineering for CdIn 2 S 4 Photoanode toward Improved Photoelectrochemical Water Splitting

Due to its suitable band energy level and small band gap, CdIn 2 S 4 is a promising photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the serious charge recombination at the back contact and photoelectrode/electrolyte interface severely hinders its PEC activity. Herein, a facile magnetron ion‐sputtering strategy is adopted to fabricate TiO 2 underlayer and NiO overlayer to modify both sides of CdIn 2 S 4 photoanode. The TiO 2 underlayer serves as an electron transport layer to promote electrons transfer from CdIn 2 S 4 to fluorine‐doped tin oxide substrate and hinder holes' transportation, thus suppressing the charge recombination at the back contact. NiO, as a p‐type semiconductor, forms a p‐n heterojunction with CdIn 2 S 4 , inducing a built‐in electric field to facilitate charge transport. Meanwhile, NiO overlayer acts as a co‐catalyst to enhance surface reaction kinetics, and thereby improves the carrier injection efficiency at photoelectrode/electrolyte interface. As a result, the optimum TiO 2 /CdIn 2 S 4 /NiO photoanode exhibits photocurrent as high as 0.6 mA cm −2 at 1.23 V versus reversible hydrogen electrode, which is about 2.3 times that of bare CdIn 2 S 4 . This work provides an effective strategy to manipulate the charge carrier dynamics to improve the PEC activity of photoanode.