Improved visible-light photoactivities of porous LaFeO₃ by coupling with nanosized alkaline earth metal oxides and mechanism insight

It is of significance to simultaneously enhance the charge separation and promote the surface reactant activation in photocatalysis. To this end, nanosized SrO coupled porous LaFeO₃ (PLFO) nanocomposites have been successfully prepared via a one-pot carbon-sphere-hard-template (CSHT) method. Compared with bare PLFO, the as-prepared optimized nanocomposite exhibits high visible-light photoactivities as shown by over 6-fold and 1.8-fold enhancement for CO₂ conversion and for 2,4-dichlorophenol (2,4-DCP) degradation, respectively. Based on the surface photovoltage spectra (SPS), fluorescence spectra (FS) related to the produced OH amount, and temperature programmed desorption (TPD) and electrochemical reduction curves, it is demonstrated that the exceptional visible-light photoactivities are mainly attributed to the large surface area due to the porous structure, and the introduced nanosized SrO which acts not only as a platform to accept high level energy electrons (HLEEs) to enhance the charge separation but also as an activator to adsorb and catalyze CO₂ (O₂) to promote the surface chemical reactions. Additionally, this efficient strategy is versatile for other alkaline earth metal oxides, such as MgO, CaO and BaO. In comparison with the different alkaline earth metal oxide modifications, it is proven that SrO is the best one to couple with PLFO, attributed to it having the most enhanced charge separation and greatest ability to adsorb and catalyze CO₂ (O₂). This work concludes that alkaline earth metal oxide modification is feasible for the promotion of the photocatalytic activity for CO₂ conversion and organic pollutant degradation.