Effective Near-Infrared Light-Driven Photocatalytic Reduction of CO2 by Dual-Site Doped Carbon Nitrides

g-C3N4 is a nontoxic, stable, and nonmetal photocatalyst that mostly absorbs solar energy in the ultraviolet region. The photocatalytic activity of g-C3N4 was considerably restricted by its low quantum efficiency and fast carrier recombination. In this work, we present a novel P-S codoped black carbon nitride (PSCN) prepared by the solvothermal method. The physicochemical and photoelectrical properties of the prepared catalysts were studied by SEM, XRD, XPS, UV-vis DRS, and PL techniques. By introducing P and S heteroatoms to the C3N4 framework, its bandgap was reduced significantly from 2.71 eV (GCN) to 1.79 eV (PSCN), and its light absorption extended from the UV zone (lambda < 420 nm) to the NIR zone (800-1500 nm). When exposed to near-infrared laser radiation (lambda = 808 nm), the catalyst demonstrates an unusual photothermal conversion, as evidenced by IR thermography. The CO yields with a PSCN photocatalyst (58.5 mu mol<middle dot>h(-1)<middle dot>g(-1)) under NIR light (lambda > 800 nm) are comparable to that irradiated by UV-vis light (300 < lambda < 800 nm, 57.0 mu mol<middle dot>h(-1)<middle dot>g(-1)), while the CO yield with GCN under full-spectrum is only 6.2 mu mol<middle dot>h(-1)<middle dot>g(-1) (UV-vis-NIR). According to DFT simulations, PSCN can lower the energy required to produce COOH*. Furthermore, compared to CO desorption, the energy barriers for forming HCO* on PSCNs were much higher; thus, the selectivity of CO2 reduction to CO was enhanced. Our research provides a new approach for constructing nonmetal photocatalysts with a wide spectral response range and photothermal synergistic catalysis.