Enhanced charge transferring through defects-mediated metal-carbon nanocomposites for efficient dye degradation under visible light

The photocatalytic efficiency of TbFeO3 photocatalyst was enhanced by generating defects, e.g., oxygen- vacancies (OVs) via Zr-doping (1-5 mol%) at the Fe site and constructing its nanocomposite. With the physiochemical, and optical characterizations catalytic efficiency of samples was tested by photo-degradation of methylene blue (MB) under visible-light irradiation. The study demonstrated that 5 mol% (ZTF-5) exhibited the highest photocatalytic potential due to the formation of OVs on the surface in maintaining charge neutrality. Later, metal-carbon CN/ZTF-5 nanocomposite was developed by coalescing ZTF-5 with g-C3N4 to improve its photocatalytic potential, which displayed 97.75 % photo-degradation in 90 min that is 1.13 and 1.20, 1.34, 1.40 and 1.51-fold higher than ZTF-5, CN, ZTF-3, ZTF-1, and TF respectively. The enhanced photocatalytic performance attributed to the presence of OVs which play a role in mediating e- h+ pairs separation in CN/ZTF-5 by lowering their recombination rate and charge-transfer resistance, verified by XPS, photoluminescence (PL), and electrochemical impedance spectroscopy (EIS) respectively. Additionally, with optimization of reaction parameters (pH, catalyst and H2O2 dose, dye concentration, and reaction time), reaction kinetics (rate constant for CN/ ZTF-5 = 0.039 min-1), scavenger experiment (center dot O2- radicals; primary reacting species), and the recycling potential of 81.23 % was achieved by CN/ZTF-5 after 4th runs. The photo-degradation mechanism of CN/ZTF-5 was explored based on band-edge potential calculated by Mott-Schottky analysis. Eventually, reaction parameters were studied using statistical analysis of response surface methodology with central composite design. This study implies that defects-engineered catalysts can enhance degradation rate and efficiency of industrial wastewater (textile and cosmetics) remarkably.