Enhanced photocatalytic degradation of Rhodamine B via iron/nickel co-doped graphitic carbon nitride: Synthesis, degradation mechanism, and DFT insights

Graphitic carbon nitride photocatalytic efficiency is hindered by limited active sites and fast electron-hole recombination. A facile two-step calcination strategy was used to fabricate iron and nickel co-doped g-C 3 N 4 (Fe/Ni-g-C 3 N 4 ) for enhanced photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. This increased specific surface area (11.2 m 2 /g for Fe 3 /Ni 1 -g-C 3 N 4 compared to 10.3 m 2 /g for pure g-C 3 N 4 ), improved visible light harvesting, and triggered a prolonged charge carrier lifetime. The Fe 3 /Ni 1 -g-C 3 N 4 catalyst showed superior performance, with a kinetic rate constant of 0.04481 min −1 , which is three times greater than that of its other counterpart photocatalysts. It also exhibited excellent stability, degrading over 90% of RhB for three consecutive cycles. Meanwhile, mechanistic study of radical quenching tests and DFT calculations showed degradation via h + radicals, initiating deethylation and hydroxylation reactions that mineralized RhB into CO 2 and H 2 O. Finally, this report provides the synergy of Fe/Ni and an avenue for efficient and stable metal-doped graphitic carbon nitride photocatalysts.