Mg₂Fe₂O₅Nanoparticle-Decorated Ca₂Fe₂O₅-CaFe₂O₄Heterostructure for Efficient Photocatalytic CO₂Conversion

In this work, a CaFe₂O₄porous network and a Mg₂Fe₂O₅nanoparticle (NP)-decorated Ca₂Fe₂O₅-CaFe₂O₄heterostructure are synthesized using the solution combustion method. Ca₂Fe₂O₅and Mg₂Fe₂O₅NPs are incorporated into the CaFe₂O₄network based on density functional theory (DFT) calculations for enhancing the CO₂adsorption of the heterostructure. With the addition of Ca₂Fe₂O₅and Mg₂Fe₂O₅NPs, this CaFe₂O₄-based heterostructure demonstrates significantly improved photocatalytic activity for CO₂conversion compared to the pristine CaFe₂O₄network. CH₄and CH₃CHO are produced, and there is no H₂detected from the photocatalytic conversion of CO₂and H₂O over the Mg₂Fe₂O₅NP-decorated Ca₂Fe₂O₅-CaFe₂O₄heterostructure. Selectivities of 81.7 and 18.3%, respectively, for CH₄and CH₃CHO are achieved in this process. DFT calculations indicate that among the three components in the heterostructure, Ca₂Fe₂O₅is the active site with the lowest activation energy for the conversion of CO₂and H₂O to CH₄. Type-II charge transfer dynamics is suggested to take place in the staggered CaFe₂O₄-Ca₂Fe₂O₅heterojunction to improve charge separation, which allows the photoelectrons to be well collected on the Ca₂Fe₂O₅side for the reduction of CO₂. Accordingly, the CO₂adsorption, charge separation, and surface CO₂conversion efficiencies are all enhanced with the incorporation of Ca₂Fe₂O₅and Mg₂Fe₂O₅into the CaFe₂O₄porous network, resulting in the boosted photocatalytic activity for CO₂conversion in the Mg₂Fe₂O₅NP-decorated CaFe₂O₄-Ca₂Fe₂O₅heterostructure.