Black phosphorus coupled black titania nanocomposites with enhanced sunlight absorption properties for efficient photocatalytic CO2 reduction

Herein, we report a facile direct solid-state reaction strategy using black phosphorus coupled black titania to prepare uniform BP-BT materials with enhanced wide-spectrum sunlight absorption properties. BP-BT possesses a typical crystalline core-amorphous shell (TiO2@TiO2-x) structure with numerous oxygen vacancies and electron-rich P dosage in the layer and exhibits excellent solar-to-chemical conversion for efficient photocatalytic CO2 reduction to CH4. Notably, the optimized BP-BT shows superior activity of CH4 formation of 16.8 mu mol g-1 h-1, a selectivity of 80.1 %, and excellent stability for CO2 transformation under solar light irradiation. The kinetic isotope effects and in situ diffuse reflectance infrared Fourier transform spectroscopy analysis reveal that the adsorption and chemical activation of inert CO2 molecule over the surface-defective and surface basic-site-modulated BP-BT are kinetically-relevant steps. The existence of crucial intermediate of CO2species from single-electron CO2 reduction route and the rate-determining step of C--O bond cleavage in photocatalytic CH4 generation were also confirmed.