A Z-scheme photocatalysis for phenol eradication from water using peroxymonosulfate activation Ag/AgBr/SCN nanocomposite

The present work was mainly focused on construction of direct Z-scheme Ag/AgBr/SCN heterostructure and their photocatalytic ability to removal of phenol using synthesized photocatalysts. Ag/AgBr/SCN photocatalyst was prepared via facile deposition-precipitation method while bare g-C3N4 (GCN) and SCN (sulphur doped g-C3N4) were prepared via simple thermal-polycondensation method. The Ag/AgBr/SCN Z-scheme heterostructure was fabricated by integration of 2D SCN with AgBr. Doping of sulphur in GCN structure has incremented the light absorption ability of GCN via reducing the energy gap to 2.64 eV from 2.7 eV. Different spectroscopic and analytical techniques have confirmed the successful formation of photocatalysts. The addition of PMS during the photocatalytic experiment has enhanced the removal efficiency of photocatalysts due to more •OH and •SO4−radicals generation. It was observed from the results that PMS assisted Ag/AgBr/SCN photocatalytic material exhibited highest removal efficiency i.e. 99% compared to other bare photocatalysts within 80 min of visible-light exposure. Proposed mechanism validated the Z-scheme charge transfer route in Ag/AgBr/SCN in accord to apt band alignment in SCN and AgBr. However, Ag metal acted as an electron mediator to just transfer the electron from CB of SCN to CB of AgBr. The transference of electron from sulphur doped g-C3N4 to AgBr through Ag improved electron transportation. This ultimately enhanced charge separation rate and reduced the charge recombination rate in Ag/AgBr/SCN nanocomposite. The proposed mechanism also presented that •OH, SO4•− and •O2− radicals were the primary reactive species during Ag/AgBr/SCN/PMS assisted photocatalytic phenol degradation process (verified through scavenging tests). Finally, the recyclability experiment confirmed the stability and reusability of the prepared photocatalyst to 5 consecutive cycles. Consequently, this work presents a new perspective to fabricate greener, cheaper and proficient visible driven photocatalytic material for wastewater detoxification and environmental remediation.