Expanded graphite supported p-n MoS2-SnO2 heterojunction nanocomposite electrode for enhanced photo-electrocatalytic degradation of a pharmaceutical pollutant

  • Eseoghene H. Umukoro, Neeraj Kumar, Jane C. Ngila, Omotayo A. Arotiba
  • Journal of Electroanalytical Chemistry, October 2018, Elsevier
  • DOI: 10.1016/j.jelechem.2018.09.027

A novel photoanode consisting of a p-n MoS2-SnO2 heterojunction anchored on EG was fabricated

What is it about?

Wastewater treatment challenges by conventional methods have necessitated the need for alternative/complementary methods that are environmentally benign and efficient especially toward recalcitrant organic pollutants. In this regard, a novel photoanode consisting of a p-n MoS2-SnO2 heterojunction anchored on expanded graphite (EG) was fabricated and employed in the photo-electrocatalytic degradation of ciprofloxacin, a pharmaceutical pollutant, in water using a current density of 0.010 A cm−2. The photoanode material was characterised with transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy and X-ray diffraction (XRD) to confirm that the nanocomposite was successfully prepared. Photoelectrochemical studies were carried out with cyclic/linear sweep voltammetry and chronoamperometry. The removal efficiency of the photo-electrocatalytic cell was determined on a UV–Visible spectrophotometer and the extent of mineralisation was measured by a total organic carbon analyser. The results obtained revealed that the SnO2 particles are nanosheets while the MoS2 particles are hierarchical microspheres having nanosheets of MoS2, and they were anchored on the interlayers of the EG sheets. Also, the p-n MoS2-SnO2 heterojunction anchored on expanded graphite (EG) was found to be photoactive and displayed a better removal efficiency and mineralisation in comparison to EG, SnO2-EG and MoS2-EG electrodes. This may be due to the formation of the MoS2-SnO2 p-n heterojunction in the MoS2-SnO2/EG nanocomposite which enhanced the light harvesting ability of the material resulting in its improved photo-electrocatalytic performance. Hence the MoS2-SnO2/EG is potentially a good photoelectrode which may be beneficial for a photo-electrocatalytic treatment of industrial wastewaters and other photo-electrocatalytic applications.

Why is it important?

To the best of our knowledge no report can be found on MoS2-SnO2 supported on expanded graphite or other carbon support for photoelectrochemical degradation. The only report where MoS2-SnO2 was used for degradation was on FTO support [46] for dye degradation. While this work reports a novel photoanode and novel analyte pollutant (antibiotic), it also strengthens the potential applicability of this hybrid in photoelectrocatalysis. We believe our work can be a premise for further investigations and applications. Herein, MoS2-SnO2 nanohybrid supported on EG was fabricated as an electrode and utilised for the photo-electrocatalytic removal of ciprofloxacin as a model pharmaceutical pollutant.

Perspectives

Dr Neeraj Kumar
Council for Scientific and Industrial Research

This work reports the synthesis and characterisation of a novel photo-electrode consisting of a p-n MoS2-SnO2 heterojunction anchored on expanded graphite (EG). This was applied in the photo-electrocatalytic degradation of ciprofloxacin as a target pharmaceutical pollutant in water. The fabricated electrode exhibited a better photo-electrocatalytic performance compared to MoS2-EG, SnO2-EG and EG electrodes for the removal of the ciprofloxacin. This could be attributed to the formation of the MoS2-SnO2 p-n heterojunction in the nanocomposite which aided charge separation and transfer, thereby resulting in the minimisation of the recombination rate of the photoinduced electrons and holes. Furthermore, the linear sweep voltammetry and photocurrent measurements revealed that the nanocomposite electrode is rendered a good photo-electrode which can be beneficial for photo-electrocatalytic treatment of industrial waste waters and other photo-electrocatalytic reactions.

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http://dx.doi.org/10.1016/j.jelechem.2018.09.027

The following have contributed to this page: Dr Neeraj Kumar