Ag_2CO_3/TiO_2, as a kind of heterojunctions, were prepared by depositing Ag_2CO_3 on the surface of TiO_2, and then characterized by X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET) method, energy dispersive X-ray spectrometer(EDS) and surface photovoltage(SPV) spectroscopy. The photocatalytic activity was evaluated in the degradation reaction of methyl orange under simulated sunlight irradiation. The results show that the separation rate of the photo-induced electron-hole pair in TiO_2 has significantl...