Z-scheme photocatalytic reaction is considered an effective strategy to promote the photogenerated electron-hole separation for significantly improving the efficiency of photocatalytic hydrogen precipitation from splitting water. In this study, a heterojunction nanocomposite material based on Zn3V2O8 (ZV) with MWCNT was prepared by a hydrothermal process. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV-visible absorption spectroscopy, and transmission electron microscopy (TEM) to understand crystal structure, morphology, and optical properties. The efficiency of the samples was evaluated for the photocatalytic H2 production under visible solar radiation using water glycerol as a sacrificial reagent. The obtained results suggest that, between ZV and ZV@MWCNT, the latter shows higher efficiency for H2 production. The maximum H2 production efficiency was found to be 26.87 μmol g–1 h–1 for ZV and 99.55 μmol g–1 h–1 for ZV@MWCNT. The synergistic effect of MWCNT to ZV resulted in improving the efficiency of charges and light-absorbing capacity, resulting in enhanced H2 production in the heterojunction nanocomposite material. The nanocomposite was stable and highly efficient for H2 production of six or more cycles. Based on the outcomes of this study, it can be observed that forming the heterojunction of individual nano systems could result in more efficient material for H2 production under visible solar energy.

In this study, zinc vanadate/reduced graphene oxide (Zn3V2O8/rGO) composite has been synthesized via a simple approach. Advanced characterization techniques (powder X-ray, scanning electron microscopy, energy dispersive X-ray spectroscopy and ultraviolet-visible (UV-vis) spectroscopy) have been used to authenticate the formation of Zn3V2O8/rGO composite. Subsequently, Zn3V2O8/rGO was applied as photo-catalyst for hydrogen generation using photo-catalysis. The Zn3V2O8/rGO photo-catalyst exhibited a good hydrogen generation amount of 104.6 µmolg−1. The Zn3V2O8/rGO composite also demonstrates excellent cyclic stability which indicated better reusability of the photo-catalyst (Zn3V2O8/rGO). This work proposes a new photo-catalyst for H2 production application. We believe that the presence of synergistic interactions was responsible for the improved photo-catalytic properties of Zn3V2O8/rGO composite. The Zn3V2O8/rGO composite is an environmentally friendly and cost-effective photo-catalyst and can be used for photo-catalytic applications.

In this study, we fabricated Zn3V2O8 and a Ag-modified Zn3V2O8 composite (Zn3V2O8/Ag) by utilizing effective and benign approaches. Further characterization techniques such as powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were explored to examine the phase and structural properties, respectively, of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag composite materials. The oxidation states and elemental composition of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag were characterized by adopting X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The optical band gaps of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag were examined by employing ultraviolet–visible (UV-vis) diffuse reflection spectroscopy. HRTEM images clearly show that ZnV@Ag NC has a hexagonal plate-like morphology. Subsequently, Zn3V2O8 and Zn3V2O8/Ag were used as photocatalysts for photocatalytic hydrogen (H2) production. It was observed that after Ag doping, the energy band gap of ZnV was reduced from 2.33 eV to 2.19 eV. EDX mapping images also show the presence of Ag, O, Zn, and V elements and confirm the formation of ZnV@Ag NC with good phase purity. Observations clearly showed the presence of excellent photocatalytic properties of the synthesized photocatalyst. The Zn3V2O8/Ag photocatalyst exhibited H2 generation of 37.52 µmolg−1h−1, which is higher compared to pristine Zn3V2O8. The Zn3V2O8/Ag photocatalyst also demonstrated excellent reusability, including decent stability. The reusability experiments suggested that ZnV@Ag NC has excellent cyclic stability for up to six cycles.

The contamination of water is increasing day by day due to the increase of urbanization and population. Textile industries contribute to this by discarding their waste directly into water streams without proper treatment. A recent study explores the treatment potential of copper oxide nanorods (CuO NRs) synthesized on a green basis in the presence of a biopolymer matrix of agar (AA) and alginate (Alg), in terms of cost effectiveness and environmental impact. The synthesized bio nanocomposite (BNC) was characterized by using different instrumental techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), ultra-violet spectroscopy (UV-Vis), scanning electron microscopy-energy dispersive X-ray-elemental analysis (SEM-EDX), transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and X-ray photoelectron spectroscopy (XPS). The optical studies revealed that immobilization of CuO NRs with Alg-Agar biopolymer blend resulted in an increase in light absorption capacity by decreasing the energy bandgap from 2.53 eV to 2.37 eV. The bio nanocomposite was utilized as a photocatalyst for the degradation of amaranth (AN) dye from an aquatic environment under visible light irradiation. A statistical tool known as central composite design (CCD) associated with response surface methodology (RSM) was taken into consideration to evaluate the optimized values of process variables and their synergistic effect on photocatalytic efficiency. The optimized values of process variables were found to be irradiation time (45 min), AN concentration (80 ppm), catalyst dose (20 mg), and pH (4), resulting in 95.69% of dye degradation at 95% confidence level with desirability level 1. The rate of AN degradation was best defined by pseudo-first-order reaction based on the correlation coefficient value (R2 = 0.99) suggesting the establishment of adsorption-desorption equilibrium initially at the catalyst surface then photogenerated •O2– radicals interacting with AN molecule to mineralize them into small non-toxic entities like CO2, H2O. The material used has high efficiency and stability in photocatalytic degradation experiments up to four cycles of reusability.

Photochemical hydrogen evolution and the degradation of synthetic dyes in water are the two key ways to unravel the issues associated with the energy and environmental sectors for sustainability. The present work deals with the use of a deep eutectic solvent for the synthesis of Ni3V2O8/N-doped reduced graphene oxide (NiV/NR hybrid). The NiV/NR hybrid, NRGO, and NiV were characterized using XRD, SEM, TEM, UV-DRS, XPS, and other photo-electrochemical techniques. The NiV/NR hybrid exhibited high efficiency towards light-driven hydrogen evolution (12,546 µmol)) compared to pristine NiV (6453 µmol) and NRGO (1935 µmol). Among the various sacrificial agents examined, TEOA showed better activity in H2 evolution. The photocatalytic degradation of anionic (Methyl orange; MO) and cationic dyes (crystal violet; CV) were evaluated and the reaction conditions were carefully optimized to attain the utmost efficiency. The efficiency of the NiV/NR hybrid was higher under visible light irradiation than UV light and able to degrade 94.6 and 96.7% of MO and CV, respectively. The results of the simultaneous degradation of dyes and total organic carbon (TOC) removal were good. Based on the obtained bandgap and Mott–Schottky plots, the mechanism of photocatalysis in the NiV/NR hybrid is discussed in detail. The reusability and stability of the NiV/NR hybrid in both H2 evolution experiments and degradation studies are excellent. The fabricated NiV/NR hybrid material could be used for multiple applications in energy and environmental applications.