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Fe2O3/g-CN heterojunction composites were successfully fabricated by a simple calcinations method using iron chloride and urea as precursors. A specific amount of Fe2O3 was incorporated on the surface of g-CN and calcinated at 400, 450, and 500 °C to obtain series of Fe2O3/g-CN (400(1), 450(2), 500(3) °C) composites. Characterization techniques were applied to measure the optical activities of Fe/CNx composites. The Fe/CN(2) sample showed a significant enhancement in the separation of photo-generated carriers under visible light due to the Fe coordination within g-CN. The composites were utilized for the first time along with parent g-CN sample for the evolution of H2 source by water splitting experiment, as well as and for photodegradation of MB under visible light illumination (λ = 420 nm). Results demonstrate that Fe/CN(2) samples exhibit a remarkable photocatalytic performance in both electron generation (HER) and holes formation, i.e. good degradation performance and as such, the corresponding degradation rate of the superior sample is 91.4 % at 60 min. Moreover, the reusability tests of Fe/CNx composites at different temperatures confirm good degradation performance and have excellent photochemical stability in terms of hydrogen evolution and removal of pollutants, respectively. With experimental results, a possible photocatalytic mechanism of Fe/CN(2) composite has been exceeded to describe the whole phenomena of photocatalysis.

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A very simple coprecipitation approach is adopted to prepare ZrO2-coated NiO on MWCNTs nanocomposites with NiO nanoparticles within 10–15 nm size. The XPS studies confirm the presence of Zr, Ni, C, and O elements in the sample, while the BET and BJH analyses reveal a typical surface area of 204.44 m2 g–1 with pores between 10 and 15 nm. The electrochemical performance studies of the ZrO2-coated nanocomposite electrode show a higher charge/discharge capacity of 688.3/688.7 mAh g–1 after 200 cycles with excellent retention capacity (96%) and cycling stability. A minor capacity fading has been observed in the rate performance of the electrodes at currents ranging from 100 to 5000 mA g–1. It also reveals that coin cells tend to maintain their maximum Coulombic efficiency of 99.9% at a low current density, revealing a notable reversible capacity. Therefore, adding MWCNTs significantly increases electrochemical performance and prevents pulverization of active materials. While structural flexibility helps in mitigating the volumetric expansion. During the cycling process, the ZrO2 coating helps improve structural stability and facilitate the diffusion of Na ions.