Highly Selective Production of Hydrogen Peroxide on Graphitic Carbon Nitride (g-C 3 N 4 ) Photocatalyst Activated by Visible Light

High Resolution Image Download MS PowerPoint Slide Photocatalytic production of hydrogen peroxide (H 2 O 2 ) on semiconductor catalysts with alcohol as a hydrogen source and molecular oxygen (O 2 ) as an oxygen source is a potential method for safe H 2 O 2 synthesis because the reaction can be carried out without the use of explosive H 2 /O 2 mixed gases. Early reported photocatalytic systems, however, produce H 2 O 2 with significantly low selectivity (∼1%). We found that visible light irradiation (λ > 420 nm) of graphitic carbon nitride (g-C 3 N 4 ), a polymeric semiconductor, in an alcohol/water mixture with O 2 efficiently produces H 2 O 2 with very high selectivity (∼90%). Raman spectroscopy and electron spin resonance analysis revealed that the high H 2 O 2 selectivity is due to the efficient formation of 1,4-endoperoxide species on the g-C 3 N 4 surface. This suppresses one-electron reduction of O 2 (superoxide radical formation), resulting in selective promotion of two-electron reduction of O 2 (H 2 O 2 formation).