Manipulating electronic structure and light absorption of carbon nitride via P-doping and local crystallization for efficient photocatalytic reduction of CO2

Graphitic carbon nitride (g-C3N4, CN) with high light harvesting and suppressed charge recombination is desired in photocatalytic reactions. Herein, locally crystalline CN (KP/CN) with photoresponse edge of 648 nm was synthesized by a two-step calcination method. First step was P-doping via calcining phytic acid and nitrogen-containing precursor. Another was local crystallinity tailoring via calcining with KSCN. The obtained KP/CN facilitated the n → π* electronic transition, exhibited improved light utilization and charge mobility. Theoretical calculations confirmed that CO2 adsorption and activation became easy on KP/CN-2. The yields of CO and CH4 under KP/CN catalysis were 58.7 and 29.0 μmol g−1, respectively, after 5 h in the presence of 0.5 mL water. This work demonstrated the synergistic enhancement of light absorption and charge carrier dissociation via doping and partial crystallization.