Enhancing photocatalytic hydrogen peroxide production by doping trace amount of azo linked C3N5 in g-C3N4 matrix

Abstract

We have fabricated a composite system by incorporating trace amount of azo linked C3N5 inside the 2D matrix of g-C3N4 system through in situ polymerization process. Detailed structural and elemental characterizations are further correlated with the underpinning photophysical processes. Results suggest that the trace amount of C3N5 inside the 2D back bone of C3N4, enhances the amount of visible light absorption along with highly efficient charge separation between the two different counterparts of the composite. The excited state free carrier dynamics have been further clarified by femto second transient absorption spectroscopy. Finally, the composite system has been utilized for photocatalytic H2O2 production. The optimized composite system shows 8.2 mmol g-1 h-1of H2O2 production with apparent quantum yield of ~28 % without using any metal site. This is one of the highest photocatalytic H2O2 production reported till date for this type of all carbon-based composite systems. The photoinduced charge separation process has been further confirmed by electrochemical impedance spectroscopy and transient photocurrent studies. The photocatalytic mechanism has been further confirmed by chemical scavenging experiments of the photoinduced free radicals.