Photogenerated Electron–hole separation–driven CO2 reduction coupled with tetracycline oxidation over LaMnO₃ nanoparticles/oxygen–etched g–C₃N₄ heterojunction: Complementary effects brought by proton transfer

Abstract

This study introduces a simple one–step in situ calcination strategy for fabricating a heterojunction of perovskite–type LaMnO3 nano–particles/oxygen–etched graphitic carbon nitride (OE–g–C3N4) to enhance photogenerated charge separation and suppress electron–hole pair recombination under visible light irradiation, which can be used for highly efficient photocatalytic CO2 reduction and elimination of tetracycline. Adjusting the ratio of LaMnO3 nano–particles enabled targeted regulation of the photocatalytic activity of LaMnO3@OE–g–C3N4 heterostructures to achieve optimal photocatalytic performance. Under the condition of photocatalytic CO2 reduction coupled with tetracycline oxidation, 0.3–LaMnO3@OE–g–C3N4 hybrids required only 40 min under visible–light irradiation to achieve complete mineralisation of tetracycline. Meanwhile, it displayed outstanding photocatalytic CO2 reduction performance with the CO and CH4 production rates of 538.75 and 26.84 μmol g−1 h−1. Additionally, it also exhibited satisfactory stability, as its photocatalytic performance remained almost unchanged after five cycles of photocatalytic experiments. The photocatalytic mechanism of CO2 reduction and tetracycline oxidation is driven by proton transfer between photo-generated electrons and photo-induced holes. Furthermore, potential intermediate products and reaction routes were also investigated using in situ DRIFTs, high–performance liquid chromatography–mass spectrometry, and DFT calculations. Quantitative structure–activity relationship–based evaluation uncovered the toxicity of photodegradation–produced intermediates. Overall, this study provides an effective strategy for constructing artificial heterojunction photocatalysts with excellent photocatalytic reduction coupled with oxidation performance for environmental remediation under visible–light irradiation.