Ion Sputtering–Assisted Double‐Side Interfacial Engineering for CdIn₂S₄ Photoanode toward Improved Photoelectrochemical Water Splitting

Abstract

Due to its suitable band energy level and small band gap, CdIn2S4 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 TiO2 underlayer and NiO overlayer to modify both sides of CdIn2S4 photoanode. The TiO2 underlayer serves as an electron transport layer to promote electrons transfer from CdIn2S4 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 CdIn2S4, 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 TiO2/CdIn2S4/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 CdIn2S4. This work provides an effective strategy to manipulate the charge carrier dynamics to improve the PEC activity of photoanode.

Recent research progress on operational stability of metal oxide/sulfide photoanodes in photoelectrochemical cells

“…ZnIn2S4 and CdIn2S4, as the most common ternary sulfide semiconductors, always present a polycrystalline mixture based on cubic and hexagonal lattices. Given their narrow Eg and obvious chemical stability, they have received extensive attention since they were first reported [180,181]. Compared with binary metal sulfides, such devices undergo photocorrosion for roughly the following reasons: (i) surface accumulation of photogenerated holes; (ii) the presence of surface states; (iii) oxidation of S elements; (iv) loss of Zn or Cd elements.…”

Two‐Dimentional Nanostructured Metal Oxide/Sulfide–Based Photoanode for Photoelectrochemical Water Splitting

“…The growth mechanism involves two steps, nucleation and oriented crystal growth, which are similar to the hydrothermal/solvothermal method. There are many high‐quality 2D metal oxides/sulfides made from CBD methods, including CdIn 2 S 4 [ 50 ] and In 2 S 3 . [ 51 ] The seed layer epitaxial growth method is conducive to grow vertically aligned 2D metal oxides/sulfides on the desired substrate.…”

“…As a result, the composite photoanode exhibited a 2.13‐fold enhanced photocurrent density compared to a bare 2D WO 3 photoanode. Furthermore, p–n heterojunctions based on 2D metal oxides/sulfides, such as In 2 Se 3 /MoS 2 [ 119 ] and CdIn 2 S 4 /NiO, [ 50 ] have been investigated for PEC water splitting.…”

CdIn2.2Sy Nanosheet-Based Photoanodes for Photoelectrochemical Water Splitting

“…The CdIn 2 S 4 photoanode was modified by TiO 2 (underlayer), which serves as an electron transporter through back contact, and NiO (overlayer) as a ptype semiconductor, which makes a p−n heterojunction with CdIn 2 S 4 , thereby making a built-in electric field to ease charge transportation. 20 Meng et al reported a CdIn 2 S 4 /In 2 S 3 bulkheterojunction photoanode to increase the charge separation efficiency and decorated it with ultrathin amorphous SnO 2 to improve the surface oxygen reaction kinetics. 21 Liang et al decorated the CQDs on the surface of hydrogenated TiO 2 for trapping the photoinduced electrons and to increase the solar light-harvesting efficiency.…”