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[Display omitted] • Orange peel was utilized for synthesis of TM doped ZnO nanoparticles. • TM doping affected the charge separation of carriers. • Ni doped ZnO nanoparticles exhibited the maximum photocatalytic degradation efficiency. • The synthesized catalysts are highly stable and can be reused for 5 cycles. The present work investigates the degradation of Amoxicillin using ZnO and Fe, Ni, Co doped ZnO nanoparticles synthesized using orange peel extract. The synthesized catalysts were characterised with the help of X-ray diffraction, scanning electron microscopy, UV–Visible and photoluminescence spectroscopy for structural and optical properties and the study of charge transport behaviour of the catalysts. The observed results indicate that the Ni doped ZnO nanoparticles exhibit superior degradation efficiencies of 80.71% and 86.21% under UV light and UV + visible light irradiation. Moreover, the slightly basic environment was found to be favourable for optimizing the degradation efficiency of the catalyst, as confirmed by the pH variation experiment. The scavenging experiments were utilized to reveal the most prominent role of hydroxyl radicals in the degradation of Amoxicillin. Additionally, a mere 10.97% reduction in degradation efficiency was observed after fours cycles of degradation experiment. The plausible pathway of amoxicillin degradation has been included into this study as well. Hence, the transition metal (TM) doped ZnO nanoparticles synthesized through waste orange peels suggest their utilization as efficient photo catalyst in Amoxicillin degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co 0.75 Zn 0.25 Fe 2 O 4 nanoparticles were successfully stacked over carbon nitride sheets. • The g-C 3 N 4 / Co 0.75 Zn 0.25 Fe 2 O 4 were tested for photo catalytic for MB degradation. • The nano hybrid exhibit excellent photo catalytic efficiency of 99.34 % in merely 60 min of experiment. • The catalysts were magnetically separable indicating their stability, and reusability. Over the years, there has been a surge in interest in the use of photocatalysts for the removal of organic pollutants in wastewater. In this work, we report the successful fabrication of magnetic Co 0.75 Zn 0.25 Fe 2 O 4 /g-C 3 N 4 nano hybrids for wastewater treatment. The produced photo catalysts were used to decompose methylene blue dye. SEM, elemental mapping, XPS, Raman, and UV–visible spectroscopy were used to validate the successful creation of the nanohybrid structure. The catalysts were synthesized in three different ferrite/graphitic carbon nitride ratios and employed for the optimization of maximum photo degradation efficiency against methylene blue dye. The optimal A1 (50%Co 0.75 Zn 0.25 Fe 2 O 4 /50%g-C 3 N 4) photo catalyst exhibited excellent degradation efficiency of 99.34% for methylene blue removal in 60 min experiment. The integration of both components in a nanohybrid favours charge separation with efficient Z-scheme charge transport via redox mediators. Scavenging investigations provide credence to superoxide and hydroxyl radicals as reactive species in MB breakdown. An appropriate mechanism with outstanding stability and confirmed reusability for the envisaged photo catalyst has been described. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen vacancies fundamentals and importance in photocatalysis. • Oxygen vacancies rich heterojunction-Synthetic strategies. • OVs rich Z-scheme and S-scheme heterojunctions- Photocatalytic mechanism. • Applications for Hydrogen production and water treatment. • The existing challenges and future perspectives. Photocatalytic removal of pollutants and energy production is a green, low cost and environment friendly technology for addressing the mounting pressure of energy crisis and environmental deterioration. Developing efficient photocatalysts is still a big challenge for accelerating the photocatalytic hydrogen production and pollutant degradation especially utilizing solar light. Therefore, constructing oxygen vacancies rich Z-scheme and S-scheme semiconductor heterojunctions emerged as a promising approach to enhance the light harvesting and increasing the redox capability of photocatalysts. This review comprehensively summarises the state of art focus on oxygen vacancy's role in photocatalysts especially in Z-scheme and S-scheme heterojunctions including synthesis process and modifications. In particular, the functions of oxygen vacancy in supporting the main processes in photocatalytic energy production and pollutant removal, such as light absorption, charge separation and conversion are highlighted in this review. The current issues and future prospective in oxygen vacancies rich heterojunctions for efficient photocatalytic removal of pollutant and energy production are also addressed. Finally, a brief discussion on challenges and future prospects is demonstrated. [ABSTRACT FROM AUTHOR]