Plasmonic ternary hybrid photocatalyst based on polymeric g-C3N4 towards visible light hydrogen generation

Abstract

Surface plasmon resonance (SPR) effect of noble metal nanoparticles (NPs) for photocatalysis has a significant enhancement. In this system, a plasmonic ternary hybrid photocatalyst of Ag/AgBr/g-C 3 n 4 was synthetized and used in water splitting to generation H 2 under visible light irradiation. 18%Ag/ AgBr/g-C 3 n 4 showed the highest photoactivity, with the efficiency of hydrogen generation as high as 27-fold to that of pristine g-C 3 n 4 . Compared to simple mixture of Ag/AgBr and g-C 3 n 4 , heterocomposite Ag/AgBr/g-C 3 n 4 showed a higher photoactivity, even though they contained same content of Ag/AgBr. We find that significant factors for enhancing properties were the synergistic effect between Ag/AgBr and g-C 3 n 4 , and the light absorption enhancing by SPR effect of Ag NPs. Ag/AgBr NPs firmly anchored on the surface of g-C 3 n 4 and their high dispersion were also responsible for the improved activity and long-term recycling ability. The structure of Ag/AgBr/g-C 3 n 4 hybrid materials and their enhancement to photocatalytic activity were discussed. Meanwhile, the possible reaction mechanism of this system was proposed.Increasing attentions to environment and energy crises have spurred intense research on solar energy transform and utilization 1-3 . Hydrogen as an environmentally friendly energy source has gained more and more attention. Photocatalytic water splitting to produce hydrogen by harnessing sunlight holds particular promise as this process is economic and environmentally friendly 4-7 . Recent years, graphene-like carbon nitride (g-C 3 N 4 ) material as a polymeric compound photocatalyst has attracted considerable attention for hydrogen generation and degradation ability of organic pollutants under visible light irradiation [8][9][10][11][12][13] . As a robust and stable visible-light-driven photocatalyst with the appropriate band energy, nontoxicity and abundance properties, it also has good chemical stability, attractive electronic structure and medium-bandgap of approximately 2.7 eV 8,14,15 . Meanwhile, g-C 3 N 4 is easily-obtained via a one-step method from cheap feed stocks, such as cyanamide 16 , dicyandiamide 17 , melamine 18 , thiourea 19 and urea 20 . Although g-C 3 N 4 emerges as a good candidate for solar catalysis because of its unique physicochemical properties. While, g-C 3 N 4 also suffers from some drawbacks, such as low visible-light utilization (only the light with the wavelength < 460 nm can be absorbed) and rapid recombination of photogenerated charges. Hence, various approaches have been proposed to overcome these glitches [21][22][23][24][25] , such as metallic and non-metallic doping, design of heterojunctions, morphology control, and construction of C or N defects. Among these, it is a key remedy to choose appropriate noble metals as co-catalyst 26,27 . Pt as a most efficient co-catalyst is used to modify g-C 3 N 4 to enhance charge separation in photocatalytic process 28,29 . However, the scarcity and high cost of Pt seriously impede its extensive applications.Recently...

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