Facile One-Pot Two-Step Synthesis of Novel in Situ Selenium-Doped Carbon Nitride Nanosheet Photocatalysts for Highly Enhanced Solar Fuel Production from CO₂

Novel in situ Se-doped carbon nitride (C3N4) nanosheets are synthesized for the first time by a facile one-pot two-step strategy. The as-prepared Se-doped C3N4 nanosheets show a high visible light driven formic acid production rate of 1.001 × 105 μmol gcat–1 h–1. It represents the highest value reported in literature for formic acid production from CO2 by visible light harvesting C3N4 photocatalysts. The exceptional photocatalytic activity is largely attributed to selenium-doped conjugated system besides porous nanosheet morphology of the photocatalyst. The presence of midgap state in carbon nitride (−0.35 V vs standard hydrogen electrode) due to Se doping is found to significantly extend the light absorption up to 570 nm thereby further enhancing light harvesting ability of the photocatalyst. The current work not only provides a facile and scalable route to synthesize highly efficient Se-doped carbon nitride (C3N4) nanosheet photocatalysts but also sheds light on devising new avenues for rational design and synthesis of potentially efficient carbon nitride photocatalysts.