Design and Comparative Studies of Z-Scheme and Type II Based Heterostructures of NaNbO3/CuInS2/In2S3 for Efficient Photoelectrochemical Applications.

Here, we report the fabrication of a new Z-scheme based core/shell/shell heterostructure of NaNbO3/CuInS2/In2S3 (core/shell/shell) for photoelectrochemical (PEC) water splitting and also for degradation of organic pollutants. We have also performed a comparative study with a modified heterostructure of NaNbO3/In2S3/CuInS2 having Type II band alignment. The PEC measurements under visible light irradiation show increased photocatalytic performance for the NaNbO3/CuInS2/In2S3 heterostructures as revealed by a high current density of ∼6.72 mA/cm2 at -1.0 V versus Ag/AgCl and low photocurrent onset potential of ∼ -110 mV in comparison to the Type II system (∼1.63 mA/cm2 and -180 mV vs Ag/AgCl). Mott-Schottky plots confirmed the n-p-n type heterojunction formation in the NaNbO3/CuInS2/In2S3 heterostructure which reduces the charge carrier recombination (revealed by PL intensity and short lifetime). The Z-scheme based system also exhibits excellent degradation efficiency (∼99.6%) of organic pollutants. This work shows that the Z-scheme charge separation mechanism in NaNbO3/CuInS2/In2S3 nanostructures is more efficient than the Type II based on NaNbO3/In2S3/CuInS2.