“Dyed” graphitic carbon nitride with greatly extended visible-light-responsive range for hydrogen evolution

• Dyed carbon nitride is synthesized by pre-dye sensitizing precursor with dyes before condensation.
• The absorption edge of dyed carbon nitride reaches near infrared range.
• The hydrogen evolution of dyed carbon nitride increases 1.7 times.
• The mechanism involved is delicately investigated.

The precursor of carbon nitride pretreated with dye sensitization (methyl orange) before condensation would possess a spectral response of the resultant product extended even to the near-infrared range. The color of the products, in this case, can be delicately controlled by the amount and kind of dyes, so the process is termed “dyeing.” Their corresponding absorption edge would reach 560 and 675 nm after introduction of 0.05 and 0.15 g dye, respectively. It is assumed that the chromophores and auxochromes that impart color to the molecules are introduced into the π-conjugated system and also extend delocalization. The highest hydrogen evolution rate of the dyed carbon nitride reached 470 μmol/g h, compared with an increase by a factor of 1.7 for bulk carbon nitride. This new concept of dyeing will inspire further investigation on developing broad spectral light-responsive photocatalysts for hydrogen production.

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