Comprehensive investigation on robust photocatalytic hydrogen production over C3N5

Carbon nitride has drawn numerous eyes in the past decade, whereas the photocatalytic performance is significantly limited by its wide band-gap (∼2.7 eV for C3N4) simultaneously. Recently, C3N5 with narrower band-gap has been reported, however, a systematically investigation on its photoactivity for H2 production has not been reported. The present work demonstrates the synthesis of C3N5 by thermal treatment of 3-amino-1,2,4-triazole, and the photocatalytic performance for H2 production of C3N5 is investigated comprehensively. Photocatalytic H2 production rate of C3N5 is ∼2.2 times higher than that of C3N4 with 1.0 wt% Pt as co-catalyst, and series of experiments are carried out to explore the behind elements accounting for the high photoactivity. Combining the results of DRS, PL and photocurrent, it is found that C3N5 possesses wider visible light absorption region, lower band-gap and quicker photogenerated e-/h+ separation efficiency. Moreover, characterizations including in-situ DRIFTS are adopted to monitor the adsorption property of H2O on C3N5, which plays a significant role in surface water reduction reaction, and higher amount of adsorbed H2O molecules on C3N5 is confirmed. The present work exhibits new insights into the high photocatalytic performance of N-rich carbon nitride catalysts.