Enhancement of ZnO catalytic activity under visible light by co-doping with Ga and Ti for efficient decomposition of methylene blue

ZnO and cobalt decorated ZnO NPs: Synthesis, photocatalysis and antimicrobial applications

The rapid growth of pollutants, both biological and non-biological, puts environmental systems in jeopardy. In view of this, the current study demonstrates the synthesis of undoped and Cobalt-doped zinc oxide nanoparticles (Co doped ZnO NPs) via co-precipitation method. The confirmation of incorporation of the Co dopant into ZnO NPs was verified through various spectroscopic and microscopic techniques. UV-absorption spectra of cobalt-doped ZnO NPs revealed a red shift with change of absorption spectra from 356 nm to 377 nm as compared to undoped ZnO NPs. XRD studies inferred that the average crystallite size of 0.5% and 1% Co-doped ZnO powder was obtained to be ∼16 nm and 14 nm respectively. A drop in band gap value from 3.48 eV to 3.30 eV provided as substantive evidence of the successful integration of Co²⁺ ions inside the ZnO matrix. FESEM and HRTEM studies revealed that the obtained ZnO NPs are in narrow size distribution (15-20 nm) with a wurtzite crystal structure. The synthesized ZnO and Co-ZnO NPs showed excellent photocatalytic and antimicrobial potency towards reactive brown dye (RB-1) and two bacterial strains, respectively. 1% Co-doped ZnO demonstrated the maximum photocatalytic activity (∼95%), in contrast to 0.5% Co-doped ZnO and undoped ZnO. Thus, the findings of this work support the developed system has a dual role as the photocatalyst, and antibacterial agent for efficient environmental remediation.

Construction of Z-scheme Ti/Ga co-doped ZnO heterostructure photocatalyst with graphitic carbon nitride for efficient visible-light-driven dye degradation

Innovative solar-driven heterostructure photocatalysts are promising for removing the organic contaminants in the water environment. In this work, a sequence of well-defined Z-scheme Ti-Ga co-doped ZnO/g-C₃N₄ (TGZ/CN) heterostructure photocatalysts were developed via a simple sol-gel method and the single-phase dispersion method in order to realize the cooperative improvement from the Ti/Ga co-doping and construction of heterostructure. The synthesized samples were analyzed by a variety of characterization techniques, and the photocatalytic activity was assessed by photodegradation of methylene blue (MB) under visible light irradiation. Compared to the ZnO and g-C₃N₄, the TGZ/CN composite demonstrated higher photocatalytic performance for the degradation of MB indicating an efficient photocatalytic degradation rate of 95.4% in 105 min under visible light. Moreover, the TGZ/CN photocatalyst exhibited excellent stability after five cycles of MB photodegradation. Furthermore, the as-prepared composites' possible photocatalytic mechanism was discussed in detail. The improved photocatalytic performance primarily resulted from the effectively reduced band gap of ZnO after Ti/Ga co-doping and the facilitated separation of photoexcited e^-/h⁺ pairs caused by the construction of Z-scheme heterojunction. This work offers novel insights in developing hybrids with highly efficient photocatalytic activity towards future environmental applications.