Chinese Journal of Catalysis ›› 2017, Vol. 38 ›› Issue (12): 1990-1998.DOI: 10.1016/S1872-2067(17)62971-1

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Selective adsorption of thiocyanate anions on Ag-modified g-C3N4 for enhanced photocatalytic hydrogen evolution

Feng Chena, Hui Yanga, Wei Luoa, Ping Wanga, Huogen Yua,b   

  1. a School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, Hubei, China;
    b State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, Hubei, China
  • Received:2017-10-07 Revised:2017-10-30 Online:2017-12-18 Published:2017-12-29
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (51472192, 21477094, 21771142) and the Fundamental Research Funds for the Central Universities (WUT 2017IB002).

Abstract:

Silver-modified semiconductor photocatalysts typically exhibit enhanced photocatalytic activity toward the degradation of organic substances. In comparison, their hydrogen-evolution rates are relatively low owing to poor interfacial catalytic reactions to producing hydrogen. In the present study, thiocyanate anions (SCN-) as interfacial catalytic active sites were selectively adsorbed onto the Ag surface of g-C3N4/Ag photocatalyst to promote interfacial H2-evolution reactions. The thiocyanate-modified g-C3N4/Ag (g-C3N4/Ag-SCN) photocatalysts were synthesized via photodeposition of metallic Ag on g-C3N4 and subsequent selective adsorption of SCN- ions on the Ag surface by an impregnation method. The resulting g-C3N4/Ag-SCN photocatalysts exhibited considerably higher photocatalytic H2-evolution activity than the g-C3N4, g-C3N4/Ag, and g-C3N4/SCN photocatalysts. Furthermore, the g-C3N4/Ag-SCN photocatalyst displayed the highest H2-evolution rate (3.9 μmol h-1) when the concentration of the SCN- ions was adjusted to 0.3 mmol L-1. The H2-evolution rate obtained was higher than those of g-C3N4 (0.15 μmol h-1) and g-C3N4/Ag (0.71 μmol h-1). Considering the enhanced performance of g-C3N4/Ag upon minimal addition of SCN- ions, a synergistic effect of metallic Ag and SCN- ions is proposed-the Ag nanoparticles act as an effective electron-transfer mediator for the steady capture and rapid transportation of photogenerated electrons, while the adsorbed SCN- ions serve as an interfacial active site to effectively absorb protons from solution and promote rapid interfacial H2-evolution reactions. Considering the present facile synthesis and its high efficacy, the present work may provide new insights into preparing high-performance photocatalytic materials.

Key words: Photocatalysis, g-C3N4/Ag, Selective adsorption, Interfacial active site, Photocatalytic hydrogen evolution