Optimizing Porosity and Heteroatom Functionalities in Amorphous Carbon-Rich g-C3N4 for Dual-Mode Photocatalysis through Solar to Green Hydrogen and Chemical Energy Conversion

Herein, we have fabricated two different types of amorphous carbon-rich g-C3N4 systems with improved heteroatom functionalities and desired porosities from highly defined amorphous carbon dots and melamine. It improves the visible light absorption and effective active sites for photocatalysis compared to the pristine g-C3N4 matrix. Details of structural and elemental properties have been investigated by transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption–desorption isotherms. This was further supported by the intricate photophysical properties of the materials. Notably, the photoinduced charge separation drastically increases with increasing the amorphous C and pyrrolic N content in the g-C3N4 matrix. Photocatalytic solar H2 production also follows the same trend. The calculated external quantum efficiency for solar H2 production has reached almost 30% for the optimized material, which is one of the highest H2 production efficiencies reported to date compared to similar all-carbon-based nanomaterials. Depending on the structural insight, tunable electronic energy level alignment, and efficient charge separation, the as-synthesized C-rich g-C3N4 systems are concomitantly utilized for the selective oxidative coupling reactions of benzylamine through the simultaneous utilization of both electrons and holes. Therefore, the currently developed all-carbon-based photocatalyst will open up new possibilities for the on-demand dual mode of photocatalysis.