Synthesis of Carbon Nitride Polymorphs by Sacrificial Template Method: Correlation between Physicochemical Properties and Photocatalytic Performance

Carbon nitride compounds (CNCs) in the form of graphitic carbon nitride (g‐C 3 N 4 ) and poly(heptazine imide) were synthesized using different metal chloride salts (MCl x ), i. e., NaCl, KCl and CaCl 2 , as sacrificial templates and by varying the MCl x to melamine molar ratios. A systematic study of their photocatalytic activity for H 2 production in relation to the physicochemical, morphological, and optical properties was carried out. Each sample was tested achieving the highest hydrogen evolution rates of about 7660 μmol g −1 h −1 , 5380 μmol g −1 h −1 and 3140 μmol g −1 h −1 using CaCl 2 , KCl, and NaCl, respectively. This work demonstrates how the synthesis of CNCs with different MCl x leads to the production of high‐performance photocatalysts due to a combination of factors as the formation of vacancies or cyano groups, a shift in the optical threshold and tuning of micro(nano)structure. The results demonstrate that, when CaCl 2 is used as a sacrificial template, porous and exfoliated g‐C 3 N 4 nanosheets are formed leading to hydrogen productions which outperform most of the previously reported g‐C 3 N 4 prepared using a single synthetic step.