Efficient capture, catalytic reduction, and energy utilization of CO2 via Mg0.50Mn1.75Fe0.75O4 nanoparticles

Spinel Mn 1.75 Fe 1.25 O 4 nanoparticles (MFO NPs) have proven to be promising ferrites for low-temperature catalytic reduction of CO 2 to carbon. However, enhancement of CO 2 reduction capacity, ordering transformation of carbon, and rational application of carbon-deposited products remain challenging. This work explored the effect of Mg 2+ doping (0.0–1.0 mol/mol) on the CO 2 reduction efficiency of MFO NPs, investigated the kinetics and mechanisms of CO 2 conversion to highly graphitized nanocarbon (HGC), and evaluated the potential of Mg X MFO NPs@HGC as lithium-ion batterie anodes. Results showed that moderate Mg 2+ doping neither destroyed the Fd-3m space group of MFO NPs but rather induced abundant Mn 4+ , Mn 3+ (B-site) ions production with high H 2 reduction activity, which promoted the generation of substantial oxygen vacancies, thereby achieving efficient CO 2 capture and reduction. Mg 0.5 MFO NPs exhibited superior CO 2 adsorption (129.13 ml/g) and reduction (151.87 ml/g) performance, and CO 2 followed an adsorption-stretching-polarization-reduction mechanism at the (111) plane. During the reduction of CO 2 by Mg 0.5 MFO NPs, the controllable synthesis of HGC (5–50 nm, 82 % graphitization) was realized by increasing the temperature (300 °C→650–660 °C) and extending the time (1 min→30 min). Massive Mn 2+ generated along with oxygen vacancies played a crucial catalytic role in the graphitization of carbon. Mg 0.5 MFO NPs with 619.29 mg/g HGC from 100 cycles of CO 2 reduction maintained an outstanding reversible capacity of 749.46mA h after 400 cycles at a current density of 0.2 A g −1 . Dense HGC on Mg 0.5 MFO NPs as buffer coating enhanced lithium-ion extraction/insertion stability. This Mg 2+ -doped manganese ferrite provides a novel route for energy utilization of greenhouse gas CO 2 . • Mg 2+ replaced Fe in Mn 1.75 Fe 1.25 O 4 , increasing Mn 4+ ion for more efficient catalysis. • Mg 0.5 Mn 1.75 Fe 0.75 O 4 showed superior CO 2 capture and reduction to carbon (C) activity. • Mg 0.5 Mn 1.75 Fe 0.75 O 4 reduced CO 2 to C of 5–50 nm with 82 % graphitization at 650–660 °C. • Mg 0.5 Mn 1.75 Fe 0.75 O 4 @C maintained 749.46 mA h reversible capacity after 400 cycles.