In situ growth strategy synthesis of single-atom nickel/sulfur co-doped g-C3N4 for efficient photocatalytic tetracycline degradation and CO2 reduction

Herein, a single-atom Ni/S co-doped g-C3N4 (Ni/S-CN-N) was prepared via thermal polymerization of urea/thiourea complexes of Ni followed by secondary calcination with NH4Cl. The photocatalytic activity of this material was evaluated by degradation of tetracycline (TC) and reduction of CO2. X-ray absorption fine structure measurements and theoretical calculations indicate that single-atom sites of Ni are anchored on g-C3N4 (CN) through Ni-O/N bonds and that they act as active centers to accumulate electrons. NH4Cl-assisted calcination effectively increased the specific surface area of the material. The apparent rate constant for TC degradation over optimized Ni/S-CN-N is 0.031 min−1, 6.0 times higher than pristine CN. Moreover, the Ni/S-CN-N exhibits a high CO2 reduction rate with H2O. The CO and CH4 yields were 58.6 and 18.9 μmol g−1, respectively within 5 h, higher than that of pristine CN (CO: 7.9 μmol g−1, CH4: 0 μmol g−1). This work provides a facile in situ growth strategy to construct CN modified with single-atom metal sites for photocatalytic applications.