Photoelectrocatalytic CO2 reduction with ternary nanocomposite of MXene (Ti3C2)-Cu2O-Fe3O4: Comprehensive utilization of electrolyte and light-wavelength

The photoelectrocatalytic reduction of CO2 to high-value-added chemicals is considered one of the most promising technologies for reducing the energy crisis and global warming. In this study, new Cu2O/Fe3O4 and Ti3C2/Cu2O/Fe3O4 ternary nanocomposites were fabricated using a simple hydrothermal method and used as photocathodes in PEC-CO2R for the first time to achieve low overpotentials, high product selectivities, and high current densities by supplying different light sources and halide ion electrolytes. The successful junctions of Ti3C2/Cu2O/Fe3O4 were determined by analytical techniques, and all the results agreed well and confirmed that the 2D MXene and CuFe mixed metal oxide had interfacial connections with efficient separation of photogenerated electrons and holes, thus supplying plentiful photoinduced electrons to the CO2RR. First-principles DFT calculations were utilized for the first time to explore the electronic structure and electron flow in ternary nanocomposites. Additionally, the unique surface area of 2D MXene provides abundant reactive sites, and the heterojunction of mixed-metal oxides with MXene effectively promotes the efficiency of light utilization. Consequently, in the new PEC-CO2R system of Ti3C2/Cu2O/Fe3O4, methanol and ethanol were used as the major products at maximum rates of 65.48072 μmol/ml and 25.88482 μmol/ml, respectively, under UV-light irradiation. Moreover, the proposed nanocomposite maintained adequate stability after one month with long-term usability. Hence, this work demonstrates the use of 2D MXenes with Cu2O/Fe3O4 ternary nanocomposites as novel and efficient catalysts for PEC-CO2R.