Tartaric Acid as an Interfacial Bridge: Constructing a Tight SnS2/CdIn2S4 Junction for Efficient Photoelectrochemical Water Oxidation

Strengthening the interfacial interaction of heterojunction photoanodes is an important route to efficient photoelectrochemical (PEC) water splitting. Herein, a SnS2/CdIn2S4 heterojunction photoanode is fabricated by a two-step solvothermal method, in which tartaric acid (TA) acts as an interfacial bridge to regulate the growth of SnS2 on trapezoid-like CdIn2S4. The optimized photoanode delivers a photocurrent density of 5.93 mA cm−2 at 1.23 V vs. RHE, approximately 6.9 times that of pristine CdIn2S4 (0.86 mA cm−2), with a maximum applied bias photon-to-current efficiency (ABPE) of 2.81%. Electrochemical impedance spectroscopy shows a reduced charge-transfer resistance, and time-resolved photoluminescence reveals a prolonged carrier lifetime. Density functional theory calculations indicate the proposed interfacial charge-transfer mechanism: the work-function difference between SnS2 (6.12 eV) and CdIn2S4 (3.95 eV) drives interfacial electron transfer from CdIn2S4 to SnS2, the charge density difference reveals electron accumulation on the SnS2 side and depletion on the CdIn2S4 side, with the interfacial charge transfer increasing from 0.33 to 0.39 e− after TA bridging, and the projected density of states (PDOS) evidences a strong electronic interaction across the junction. This organic-molecule-assisted interfacial bridging offers a facile route for designing the interfaces of sulfide photoanodes.