Abstract: As a cocatalyst, silver can enhance the photoelectrons migration and has found wide application in a variety of photocatalytic reduction reactions such as water splitting hydrogen generation, CO2 reduction, heavy metal ion reduction, etc. However, to the best of our knowledge, no unconcealed work has concerned N2 photofixation by using Ag-loaded catalysts. Our present work aimed to prepare a series of Ag-loaded g-C3N4(Ⅰ)/g-C3N4(Ⅱ) isotype heterojunction catalysts differing in Ag content (Ag(x%)-CN, x=0.5,1,2,4) and estimate their N2 photofixation performance. The means of XRD, TEM, UV-Vis, XPS, Raman, PL, EIS and photocurrent response were involved in the characterization. Our experiment confirmed the existence of silver on the catalyst surface as metal state, and revealed the acting mechanism of the loaded silver cocatalyst: the plasma effect of silver promotes the visible-light absorption so that the reaction system can produce more photogenerated electron-hole pairs, and on the other hand, the photoelectrons migration between g-C3N4 and Ag improves the electron-hole separation efficiency of the composite catalyst. The NH4+ ge-neration rate of the Ag-loaded g-C3N4(Ⅰ)/g-C3N4(Ⅱ) isotype heterojunction composite catalyst was determined to be 1.36 mg·L-1·h-1·g-1cat with a dramatical increment compared to that of g-C3N4(Ⅰ)/g-C3N4(Ⅱ) without silver-loading (MU-CN,0.59 mg·L-1·h-1·g-1cat). This catalytic performance is equivalent to the Pt-loaded catalysts, and moreover, 4.9 or 3.4 times higher than g-C3N4prepared by exclusively using melamine or urea. In addition to nitrogen fixation, the Ag-loaded g-C3N4(Ⅰ)/g-C3N4(Ⅱ) isotype heterojunction catalysts also exhibited excellent catalytic performance in the reaction of photocatalytic reduction of oxygen to hydrogen peroxide.
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2018, Vol. 32 
