Construction of indirect dual S-scheme heterojunction CN/AP/AW mediated by Ag nanoparticles enables efficient CO2-to-CH4 photoreduction

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The highly selective product generation of photocatalytic CO2 reduction is greatly hampered by the multi-electron transfer process. In this work, Ag nanoparticle mediated indirect dual S-scheme compact heterojunction CN/AP/AW was successfully prepared through varying the ratio of Na2HPO4·12H2O and Na2WO4·2H2O. In pure water, the formation rate and selectivity of CH4 reached 18.49 μmol·g−1·h−1 and 94.3 % under simulated sunlight, with a sharp contrast to CN without CH4. The multi-channel directional transfer of electrons was realized by the construction of heterojunction, which also overcomes the inherent low REDOX capacity issues of conventional type-I and type-II heterojunction. In addition to addressing the weak interfacial contact that often occurs in terpolymer, Ag nanoparticles further accelerate electron transfer as an electron capturer, resulting in rapid unwanted electron-hole recombination. Possible reaction pathways and the cause of high selectivity were predicted by in situ FT-IR. This work provides guidance for the directional and efficient generation of CO2-to-CH4.