Constructing a ternary H2SrTa2O7/g-C3N4/Ag3PO4 heterojunction based on cascade electron transfer with enhanced visible light photocatalytic activity

A novel and highly efficient ternary H2SrTa2O7/g-C3N4/Ag3PO4 heterojunction was fabricated via simple impregnation and ion exchange methods with active performance for the degradation of methyl orange (MO) under solar-like irradiation. The optimal result for the binary composite was obtained for a H2SrTa2-O-7/g-C3N4-60 wt% system. The incorporation of Ag3PO4 led to a further improvement in the photocatalytic performance, as compared to the binary composite and their single components, with values of around 45.18, 44.17 and 38.23 times higher than those of pristine H2SrTa2O7, g-C3N4 and H2SrTa2O7/g-C3N4, respectively. It was found that MO solution (20 mg L-1) could be photo-degraded within 8 min with 50 mg of the H2SrTa2O7/g-C3N4/Ag3PO4 composite. This enhanced photocatalytic behavior can be mainly ascribed to the prominently promoted charge separation efficiency, the matched band-edge positions, the extension of the absorption range and the synergistic effect among H2SrTa2O7, g-C3N4 and Ag3PO4. In addition, X-ray photoelectron spectroscopy and Raman spectroscopy results confirmed a strong interface interaction between H2SrTa2O7, g-C3N4 and Ag3PO4, which greatly promoted the photocatalytic activity due to the improved separation of photoinduced charge carriers. This work presents a plausible mechanism via active species trapping experiments and electron spin resonance measurements demonstrated that photogenerated holes (h(+) and superoxide radicals (center dot O-2(-)) play a crucial role in the photodegradation reaction under visible light irradiation. Thus, the proposed synthetic method for the fabrication of H2SrTa2O7/g-C3N4/Ag3PO4 with superior photocatalytic activity provides new insights for the design of ternary photocatalysts with an ideal heterojunction and wide spectral response.