ABSTRACT
This study demonstrates the synthesis of titanium oxynitride (TiOxNy) via a controlled step-annealing of commercial titanium nitride (TiN) powders under normal ambience. The structure of the formed TiOxNy system is confirmed via XRD, Rietveld refinements, XPS, Raman, and HRTEM analysis. A distinct plasmonic band corresponding to TiN is observed in the absorption spectrum of TiOxNy, indicating that the surface plasmonic resonance (SPR) property of TiN is being inherited in the resulting TiOxNy system. The prerequisites such as reduced band gap energy, suitable band edge positions, reduced recombination, and enhanced carrier-lifetime manifested by the TiOxNy system are investigated using Mott-Schottky, XPS, time-resolved and steady-state PL spectroscopy techniques. The obtained TiOxNy photocatalyst is found to degrade around 98% of 10 ppm rhodamine B dye in 120 min and produce H2 at a rate of â¼1546 µmolg-1h-1 under solar light irradiation along with consistent recycle abilities. The results of cyclic voltammetry, linear sweep voltammetry, electrochemical impedance and photocurrent studies suggest that this evolved TiOxNy system could be functioning via plasmonic Ohmic interface rather than the typical plasmonic Schottky interface due to their amalgamated band structures in the oxynitride phase.
Subject(s)
Light , Titanium , Sunlight , Titanium/chemistryABSTRACT
Exploitation of the novel, robust, and advanced photocatalytic systems with high efficiency is the present demand for clean, green, and sustainable energy production. Carbon quantum dots (CQDs) have attracted tremendous interest in efficient H2 evolution from photocatalysis due to its remarkable visible-light harvesting and electron transport properties. Here, for the first time, a smart ternary nanocomposite comprises encapsulated CQDs with LaFeO3 spherical nanoparticles and CdS nanorods is synthesized by a simple hydrothermal procedure for the efficient photocatalytic H2 evolution under sunlight illumination. PXRD, FT-IR, FE-SEM, TEM, and XPS studies are performed to ensure the successful fabrication of ternary LaFeO3/CdS/CQD nanocomposite. The efficient H2 evolution rate (HER) of 25,302 µmol h-1 gcat-1 is achieved for LaFeO3/CdS/CQD nanocomposite, which is 602.4, 2.6, 29.8, 2.0 and 1.1 times higher than that of pristine LaFeO3, pristine CdS, and composites such as LaFeO3/CdS, LaFeO3/CQD, and CdS/CQD. Photocurrent and lifetime PL studies reveal, encapsulation of CQDs with the LaFeO3/CdS heterojunction can facilitate easy and efficient separation of photo-generated excitons. Altogether the fabrication of CQDs provides an ideal avenue for the development of high potential advanced photocatalytic systems for sustainable H2 production with remarkable efficiencies.
ABSTRACT
Design and synthesis of efficient photocatalyst systems for a large volume of hydrogen (H2) evolution under solar light is still a great challenge. To obtain high photocatalytic activity, graphene-based semiconductor photocatalysts are gaining heightened attention in the field of green and sustainable fuel production due to their good electronic properties, high surface area and chemical stability. Herein, we demonstrate an efficient, novel and smart architecture of a graphene-based ZnIn2S4/g-C3N4 nanojunction by a simple hydrothermal process for H2 generation. In the present study, graphene (G) is chosen as the electron mediator and ZnIn2S4 (ZIS) and g-C3N4 (CN) are chosen as two different semiconductor photocatalysts to construct a smart architecture for the ternary photocatalytic system. Different characterization techniques such as XRD, TGA, FT-IR, SEM, TEM, HR-TEM, XPS, BET, and UV-vis DRS were employed to ensure the successful integration of graphene, ZnIn2S4, and g-C3N4 in the nanocomposite. As a result, high and efficient H2 evolution (477 µmol h-1 g-1) is attained for the graphene-based ZnIn2S4/g-C3N4 nanocomposite. Transient photocurrent experiments, ESR, PL, and time-resolved PL studies suggested that the intimate ternary nanojunction effectively promotes fast charge transfer and thereby enhances photocatalytic H2 evolution.
