Fabrication of TiO₂/CdS/Ag₂S nano-heterostructured photoanode for enhancing photoelectrochemical and photocatalytic activity under visible light

Abstract

Wide optical absorption window, long lived and high charge carrier transfer efficiency are the prime characteristics towards the accomplishment of remarkably efficient photocatalysts. In this context, we have synthesized TiO₂/CdS/Ag₂S core/shell/shell (CSS) heterostructures by using ion-exchange method. The photoelectrochemical (PEC) measurements unveiled appreciably increased PEC water splitting performance of the CSS heterostructure (used as photoanodes), as indicated by high photocurrent density of ∼ 7.6 mA/cm² at 1.0 V versus Ag/AgCl and low photocurrent onset potential of ∼ 0.1 V as compared to pristine TiO₂ nanorods. Mott-Schottky analysis evident the p-n junction features of heterostructures that strengthen the separation of electron and holes. We have investigated the exciton dynamics with photoluminescence (PL) and time correlated single photon counting (TCSPC) studies. The diminished PL intensity and shorten average lifetime (τ_avg) in CSS heterostructures is a clear manifestation of suppression of charge carrier recombination as well as efficient charge carrier transfer from CdS (shell) to TiO₂ (core). Thus, both factors prolonged and efficient transfer of visible light driven charge carriers led to phenomenal photoactivity of TiO₂/CdS/Ag₂S based CSS heterostructures towards the degradation of toxic organic pollutants and PEC water oxidation. We anticipate that the architecture of CSS hetrostructures will provide a new paradigm in the realm of photocatalysis.