Accelerated charge transfer via a nickel tungstate modulated cadmium sulfide p–n heterojunction for photocatalytic hydrogen evolution

Abstract

Improving the efficiency of charge separation is an important aspect in photocatalysis. With NiWO₄ modulation, the results of the Mott–Schottky test, short fluorescence lifetime (1.87 ns), faster electron transfer rate constant (K_ET = 2.82 × 10⁸ s⁻¹), larger efficiency of electron injection (η_inj = 52.7%), high photocurrent response, smaller transfer resistance (R_film = 2785 Ω cm²) and reaction resistance (R_ct = 1.74 Ω cm²) showed that a new interface electric field was established and a more effective thermodynamic charge transfer path was formed. This evidence greatly supported the fact that the separation and transfer of space charges over CdS p–n were accelerated via NiWO₄ modulation. The [CdS/NiWO₄ (30%)] sample had the best H₂ production performance, namely, the maximum H₂ production in 5 hours was 757 μmol, which was 7.35 times higher than that of pure CdS nanorods. Moreover, a series of characterization results also showed that the NiWO₄ decorated CdS p–n heterojunction improved the efficiency of photo-generated charge separation and the SEM, XRD, TEM, EDX, XPS, UV-vis DRS, transient fluorescence, electro-chemistry etc. results were in good agreement with each other.