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

Improving the efficiency of charge separation is an important aspect in photocatalysis. With NiWO 4 modulation, the results of the Mott–Schottky test, short fluorescence lifetime (1.87 ns), faster electron transfer rate constant ( K ET = 2.82 × 10 8 s −1 ), larger efficiency of electron injection ( η inj = 52.7%), high photocurrent response, smaller transfer resistance ( R film = 2785 Ω cm 2 ) and reaction resistance ( R ct = 1.74 Ω cm 2 ) 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 NiWO 4 modulation. The [CdS/NiWO 4 (30%)] sample had the best H 2 production performance, namely, the maximum H 2 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 NiWO 4 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.