A g-C 3 N 4 thin film was synthesized by a liquid-based reaction onto ITO substrate via the calcination treatment. The resultant electrode was used as photoanode for photoelectrocatalytic (PEC) oxidation of Ag cyanide complexes with simultaneous Ag recovery, which was enhanced with the addition of H 2 O 2 . Surface variation of the g-C 3 N 4 photoanode and titanium cathode was analyzed using SEM, XRD, and XPS techniques. It was observed that, with the cyanide oxidation, Ag oxides and metal Ag were deposited onto the g-C 3 N 4 photoanode and titanium cathode, respectively. The photoelectrochemical response of the g-C 3 N 4 photoanode was obviously increased after the AgO deposition. ESR and trapping experiments confirmed the existence and roles of • O 2 − and • OH in the PEC oxidation process. The photogenerated electrons from g-C 3 N 4 could be captured by • O 2 − and H 2 O 2 , generating • OH radicals for oxidizing the Ag cyanide complexes. Meanwhile, the deposition of AgO species onto the g-C 3 N 4 surface increased its electrical conductivity and the migration rate of the photogenerated electrons. Deposited AgO can also enhance the production of active radicals, leading to an increased PEC activity toward the cyanide destruction.
Ag-Doped graphitic carbon nitride films (Ag/g-C 3 N 4 ) were synthesized easily onto ITO substrates by a liquid-based reaction process. Ag/g-C 3 N 4 films were comprehensively characterized by SEM, HRTEM, XRD, UV/vis DRS, and XPS. The results indicated that Ag and Ag 2 O disperse homogeneously in the matrix of the g-C 3 N 4 film. The photocurrent response of the Ag/g-C 3 N 4 films increased remarkably with increasing Ag content and the best performance was observed with the sample of Ag/g-C 3 N 4 (1 : 10).The Ag/g-C 3 N 4 films exhibited a high photoelectrocatalytic activity for the degradation of methylene blue. The enhancement of photoelectrocatalysis owing to more visible light could be harvested and photogenerated electron and interfacial electron could transfer more easily after modifying Ag in the g-C 3 N 4 film. Thus, a possible photoelectrocatalysis mechanism was proposed. Beside g-C 3 N 4 , electronhole pairs could be generated by Ag under visible light irradiation, and the photogenerated electron was captured by O 2 or cO 2 À and then forms cOH radicals.
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