In situ synthesis of polymetallic Co-doped g-C3N4 photocatalyst with increased defect sites and superior charge carrier properties

Preparation of Fe and Pd co-doped g-C3N4 was described, using dicyandiamide monomer, and [1, 1′-Bis (diphenylphosphino) ferrocene] dichloropalladium (II) as precursor. X-ray powder diffraction, Fourier transform infrared spectra, Raman spectra and transmission electron microscopy were used to confirm the formation of bulk Fe-Pd/C3N4, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy were used to analysis the chemical states and element content of Fe-Pd/C3N4. N2 adsorption and desorption isotherms, UV–vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photoluminescence and Mott-Schottky capacitance measurement were used to further investigate the semiconducting properties of Fe-Pd/C3N4. The results indicated that the addition of dopants enriched the nitrogen content of graphitic carbon nitride, induced more structural defects, expanded the surface area, decreased the band gap energy, reduced the charge-transfer resistance, raised the flat band potential and restrained the recombination of photogenerated electrons and holes. Consequently, Fe and Pd co-doped g-C3N4 exhibited higher Rhodamine B photodegradation rate than raw g-C3N4. The most possible coordination sites of Fe and Pd were inferred as the CNHC defect sites.