Dual roles of [NCN]2- on anatase TiO2: A fully occupied molecular gap state for direct charge injection into the conduction band and an interfacial mediator for the covalent formation of heterostructured g-C3N4/a-TiO2 nanocomposite

Dipak B. Nimbalkar, P. V.R.K. Ramacharyulu, Smruti R. Sahoo, Jun Ru Chen, Chun Ming Chang, Amarendra N. Maity, Shyue Chu Ke

Research output: Contribution to journalArticle

Abstract

When low density of melamine is calcined with a-TiO2 at 550 °C, two FT-IR peaks observed at 2048 and 2066 cm−1 are assigned to NCN2- covalently attached to a five-coordinated Ti atom and an oxygen vacancy, respectively, complemented by DFT computation. Admixture of NCN2- HOMO(π2p, 87.5 %) with the high energy Ti(3d, 12.5 %) destabilizes and upshifts the NCN2- HOMO into the a-TiO2 bandgap. A five-line EPR pattern derived from 71 % of atomic spin density localized on two equivalent 14N nuclei, observed under sub-bandgap excitation, verifies the presence of a molecular gap-state. The NCN2--a-TiO2 exhibits excellent H2 production at a rate of 5101 μmol.h-1.g-1. Upon increasing melamine concentration, the rapid and simultaneous decreases of NCN2- FT-IR and NCN1- EPR signals accompanied by transitions of other spectroscopic data to those characteristic of tri-s-triazine demonstrate that the formation of heterostructured g-C3N4/a-TiO2 proceeds via the intermediacy of NCN2--a-TiO2, thereby a mechanism is proposed.

Original languageEnglish
Article number119036
JournalApplied Catalysis B: Environmental
Volume273
DOIs
Publication statusPublished - 2020 Sep 15

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Environmental Science(all)
  • Process Chemistry and Technology

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