Plasma-assisted doping of nitrogen into cobalt sulfide for loading cadmium sulfide: A direct Z-scheme heterojunction for efficiently photocatalytic Cr (VI) reduction under visible light

A direct Z-scheme heterojunction has been constructed by loading cadmium sulfide (CdS) on cobalt sulfide doped with nitrogen (N-CoSx) by N-2 plasma treatment for efficient photocatalytic Cr(VI) reduction under visible light. It was discovered that the resulting CdS/N-CoSx nanocomposites could present different photocatalytic performances controllably depending on the plasma treatment time and CdS-to-N-CoSx ratios. Especially, the one with 5-min plasma treatment and 8/1 M ratio could exhibit the highest Cr(VI) photoreduction efficiency, which is over four and two folds higher than those of pristine N-CoSx and CdS, respectively. Herein, the plasma-assisted N doping could not only increase the surface wettability and conductivity of CoSx but also decrease its Fermi level for improving the photocatalytic Cr(VI) reduction. More importantly, a direct Z-scheme heterojunction could be constructed by the combination of CdS and N-CoSx with suitable band structures, which could further booster the charge separation and transferring, without sacrificing the redox capacity of photogenerated carriers. The enhanced photocatalytic activity and stability of CdS/N-CoSx nanocomposites could thereby be expected for Cr (VI) reduction, with the efficiency up to 100% within 25 min. Such a direct Z-scheme heterojunction created by the plasma treatment route may promise for the large-scale applications for the removal of various toxic pollutants in the environmental remediation field.

Automated summary

A direct Z-scheme heterojunction was constructed by loading CdS on nitrogen-doped cobalt sulfide (N-CoSx) through N-2 plasma treatment, leading to enhanced photocatalytic Cr(VI) reduction efficiency. The CdS/N-CoSx nanocomposites showed improved performance due to plasma-assisted N doping, forming suitable band structures for efficient charge separation and transferring. The resulting nanocomposites exhibited up to 100% Cr(VI) reduction efficiency within 25 minutes, making them promising for large-scale applications in environmental remediation.