Enhanced photocatalytic performance of K/O-co-doped crystalline carbon nitride for sulfamerazine degradation and CO2 reduction.

Development of efficient photocatalysts for organic pollutant degradation and CO2 resource utilization holds significant importance for environmental governance and carbon neutrality. In this study, potassium/oxygen co-doped crystalline carbon nitride (K/O-CCN) was synthesized via a LiCl/KCl molten salt method for sulfamerazine (SMR) degradation and CO2 reduction. K/O-CCN photocatalyst exhibited a great improvement in visible-light response (visible-light response red-shifted from 478 to 492 nm) and electron-hole pair separation/migration due to the synergistic effect of K/O co-doping and crystallization. Under simulated solar light irradiation, K/O-CCN exhibited a SMR degradation rate (98.7%, 0.0312 min-1) 5.9 times higher than that of pristine g-C3N4 and a CO2 reduction rate to CO (1.6 μmol g-1·h-1) 3.3 times greater than that of pristine g-C3N4. Capture experiments confirmed that e- was the primary reactive species for SMR degradation. This study presents a synergistic strategy for element doping engineering and band structure modulation in designing carbon nitride-based photocatalysts, exhibiting their potential in environmental remediation and carbon cycle applications.