Sodium doped flaky carbon nitride with nitrogen defects for enhanced photoreduction carbon dioxide activity

Sodium doped flaky carbon nitride (g-C₃N₄) with nitrogen defects (bmw-DCN-x) were synthesized via two steps method to enhance photocatalytic reduction of carbon dioxide (CO₂). After ball milling and calcination, dicyandiamide was evenly dispersed on the sodium chloride (NaCl) template to form a flaky structure. The NaCl not only provided part of sodium (Na) source for Na doped g-C₃N₄, but also introduced a large number of nitrogen (N) defects. Meanwhile, sodium hydroxide (NaOH) significantly enhanced Na doping. The bmw-DCN-30, a proportion of modified g-C₃N₄, showed heightened photo-reduction CO₂ performance, with satisfactory carbon monoxide (CO) and methane (CH₄) productivity at a rate of 30.6 μmol·g^-1·h^-1 and 5.4 μmol·g^-1·h^-1 respectively. This productivity was 15 and 11 times as much as that of bulky g-C₃N₄ (BCN). The related characterizations confirmed that N defects produced more reactive sites and enhanced the adsorption capacity of carbon nitride to CO₂. The accompanying Na doping and flaky structure characteristics improved the optical absorption ability and the effective separation of photogenerated carriers. Accordingly, this work provides further insights into constructing modified materials based on carbon nitride for CO₂ reduction.