Abstract
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.