This study explores the preparation of Ag plasmons-sensitized magnetic-Fe 3 O 4 integrated TiO 2 (Ag−Fe 3 O 4 @TiO 2 ) ternary nanocomposites and their defectinduced electron storage properties to exploit their photocatalytic memory effect toward dye degradation and H 2 generation under light and dark conditions. The crystalline phase formation and elemental states of the individual materials and elements in the nanocomposite are analyzed using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The existence of Ti and Fe ions with dual oxidation states of Ti 4+/3+ and Fe 3+/2+ , respectively, is observed by XPS, which revealed the presence of defects in the system. The observed red shift along with a distinct plasmonic band (corresponding to metallic Ag nanoparticles) in the UV−visible absorption spectrum and the observed modified radiative recombination emission in the PL spectrum confirmed the plasmon-driven visible light activity along with the improved carrier separation and transfer characteristics in the synthesized ternary composite. Accordingly, the Ag− Fe 3 O 4 @TiO 2 photocatalyst degraded almost 100% of MB (methylene blue) and RhB (rhodamine B) dyes under simulated solar light in 90 min, while it is found to be around 42% and 36% in 60 min under dark conditions, respectively (which is preirradiated for 60 min). Further, it produced H 2 at the rate of 911 μmol g −1 h −1 under light conditions and is decreased to ∼96 μmol g −1 h −1 under dark conditions which is preirradiated for 1 h. However, when the composite is preirradiated for 3 h, it showed a maximum H 2 evolution of 144 μmol g −1 h −1 under dark. Further, the photocurrent and electrochemical impedance under light and dark conditions suggested the mechanism of photocatalytic charge storage and transfer process in the composite. Although the photocatalytic memory effect of the composite is meager toward H 2 production due to the insufficient potential of the stored−released electrons to reduce the protons (2H + ) to H 2 under dark conditions, their degradation efficiency is considerably good.

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In this study, titanium oxynitride with empirical composition of TiON is developed using a sol−gel and ammoniagas-assisted thermal nitridation process. The obtained TiON phase is employed as the photoanodic electron transport layer (ETL) in a silver bismuth sulfide (AgBiS 2 ) quantum-dot-sensitized solar cell (QDSSC) device and compared to a QDSSC consisting of commercial TiO 2 as the ETL. The obtained X-ray photoelectron spectroscopy spectra and Mott−Schottky plots of the samples suggested that the valence and conduction bands of TiON are significantly shifted (E VB = 2.9 eV and E CB = −0.3 eV) with respect to that of TiO 2 (E VB = 1.88 eV and E CB = −0.51 eV), which eventually decreased its band gap energy to 2.46 eV compared to TiO 2 (3.2 eV). A decrease in the charge transfer resistance (R ct = 38.2 Ω) and improvement in carrier lifetime (τ = 5.3 ms) are observed in the developed TiON device. The work also endorses the use of eco-friendly green quantum dots of AgBiS 2 as photoabsorbers in solar cells. Although the photovoltaic performance is not found to be greater, the demonstration of the enhanced performance of the TiON-based device with ∼50% enhancements, owing to its improved open circuit voltage and current density by 20 and 35%, is achieved in this work. Titanium oxynitride can, hence, be considered a suitable alternative to existing commercial TiO 2 in all applications that involve solar energy conversion.