The development of highly efficient and cost-effective multifunctional photocatalysts is of current global interest because these photocatalysts have the potential to address the energy and water crisis. Herein, an efficient calixarene-based Calix@Nb2CTx/g-C3N4 (Cx–Nb–CN) photocatalyst was prepared through the formation of covalent bonds between the calixarene (Cx–COCl), g-C3N4 (CN), and Nb2CTx MXene. Enhanced optoelectronic and photoelectrochemical (PEC) properties were observed upon introducing Cx–COCl calixarene and Nb2CTx complexes to the g-C3N4 (CN) photocatalyst.

The XPS valence band measurements demonstrated the narrowing of the energy band gap for the composites due to the downshifting and upshifting of the CB and VB, correspondingly. Due to the sensitization effect, the Cx–CN presented superior photocatalytic properties relative to the pristine CN. Moreover, reduced charge transfer resistance (Rct = 110.7 Ω cm2) and the highest photocurrent density (Jp = 7.95 mA/cm2) were observed for the Cx–Nb–CN–5 heterostructure. The Schottky-heterostructures Cx–Nb–CN–1, Cx–Nb–CN–3, and Cx–Nb–CN–5 presented high linear sweep current densities (JLSV) of 8.61, 12.39, 14.04 mA/cm2 signifying excellent light utilization and efficient separation of charge carriers, respectively.

  • Photoelectrochemical (PEC) measurements were conducted using electrochemical impedance spectroscopy(EIS) methods through a standard three-electrode set-up on an Autolab PGSTAT204 using Nova 2.1.5 software
  • Proton nuclear magnetic resonance(1H NMR) was used to conduct a step-by-step trace analysis of the changes in protons and the formation of cone structure upon introducing the ligands to the Cx–OH.
  • Scanning electron microscopy (SEM) was employed to evaluate the microstructure and characteristic morphologies of the prepared photocatalysts.
  • Energy dispersive spectroscopy (EDS) was employed to assess the elemental compositions of the prepared photocatalysts.
  • Water contact angle analysis was carried out to evaluate the wettability(hydrophilicity and hydrophobicity) of the prepared materials.
  • Ultraviolet-Visible diffuse reflectance spectroscopy (UV-Vis DRS) was conducted to evaluate the optical light absorption abilities which can be used to assess the electronic structure of the photocatalysts.
  • In order to evaluate the photocatalytic efficiencies of the fabricated pristine and supramolecular-based Schottky-heterostructure photocatalysts, photoelectrochemical (PEC) properties were studied using EIS
  • Surface charge and agglomeration rate measurements of the as-prepared materials were conducted to assess the colloidal stability of the suspended particles in aqueous media.

The fabricated photocatalyst exhibits excellent physicochemical and photocatalytic properties with the potential to facilitate host-guest complexation towards environmental detoxification and energy conversions.

The fabricated heterostructure presented CB and VB with excellent redox band potential and narrow energy band, which makes it suitable for a wide range of photocatalytic applications such as photo–oxidation and –reduction of various gases and wastewater pollutants. Lastly, this study demonstrates the use of calixarene supramolecule as a sensitizer and a potential host-guest in a Schottky-heterojunction for photocatalysis.

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