Vertically Grown Cd-ZnIn_2.2S_y Nanosheets for Photoelectrochemical Water Splitting

To attain a sustainable energy source, in the present study, a visible light active semiconductor, ZnIn2.2Sy is developed initially and surface engineering is carried out to grow Cd-ZnIn2.2Sy following a multistep method. A hydrothermal technique is followed for the synthesis of vertically grown 2D nanosheets of visible light active photoanode ZnIn2.2Sy. Further, the cation exchange method is followed to synthesize Cd-ZnIn2.2Sy nanosheets for photoanodic application in photoelectrochemical (PEC) water splitting. In PEC water splitting, vertically grown 2D nanosheets of Cd-ZnIn2.2Sy show improved photoactivity compared to bare ZnIn2.2Sy by virtue of surface engineering. The vertically grown 2D-nanosheets efficiently absorb visible light through multiple reflection and scattering which results in more light and matter interaction. The optimized Cd-ZnIn2.2Sy nanosheets can generate a photocurrent density of 5.85 mA/cm2 at an applied potential “0.78” V vs RHE under back illumination. The photoconversion efficiency legitimizes the superiority of Cd-ZnIn2.2Sy nanosheets, η% is ∼3.10 at 0.53 V vs RHE for Cd-ZnIn2.2Sy whereas, in the case of ZnIn2.2Sy it is only 2.74% at 0.51 V vs RHE. After the development of Cd-ZnIn2.2Sy, the carrier density enhances nearly 4 times that ZnIn2.2Sy. Cd-ZnIn2.2Sy avails higher carrier density, faster charge transportation, and a wide space charge layer. The widening of the space charge layer is confirmed from the calculation of flat band potential. Both ZnIn2.2Sy and Cd-ZnIn2.2Sy nanosheets show excellent stability under continuous back illumination for 1 h.