Molybdenum atomic sites embedded 1D carbon nitride nanotubes as highly efficient bifunctional photocatalyst for tetracycline degradation and hydrogen evolution

Metal single atom catalysts (MSACs) stabilized by nitrogen in carbon nitride are intriguing photocatalysts for energy and environmental applications. However, the synergistic effect of simultaneously tailoring the carbon nitride nanostructure and fabricating single metal atoms has not been explored for photocatalysis. Herein, we report the facile synthesis of Mo atomic sites on porous carbon nitride nanotubes (Mo1@CNNTs) obtained by template free polymerization of urea and melamine monomers. AC-HAADF-STEM image confirmed the existence of isolated Mo atoms, while XAS analysis revealed the formation of unique atomic Mo-N3 structures on CNNTs. Incorporation of Mo atomic sites into CNNTs modulated electronic and band structure and thus improved light harvesting, charge separation, and transfer. The synergy of 1D nanotube structure and distinct atomic Mo sites turned Mo1@CNNTs as a highly efficient bifunctional photocatalyst for hydrogen evolution and tetracycline degradation. On one side Mo1@CNNTs demonstrated hydrogen evolution rate of 4861 µmol.h−1.g−1, while on the other hand Mo1@CNNTs achieved 97.3% TC degradation under visible light irradiation. DFT investigations revealed that induction of unique Mo atomic sites not only tuned the electronic structure of CNNTs, but also localized photoexcited electrons around Mo atoms to activate O2(ads) and generate reactive species (.O2–/.OH) for TC degradation. We believe that our findings are promising and will open new opportunities for the design of novel photocatalyst for a sustainable future.