Growth kinetic control over MgFe2O4 to tune Fe occupancy and metal–support interactions for optimum catalytic performance

Abstract

Manipulating the growth behavior of nano-sized supports is proved to have extremely favorable effects for optimizing the performance of hybrid catalysts. Herein, we investigated the growth kinetics of MgFe₂O₄ and revealed its size-dependent behavior of Fe occupancies at octahedral and tetrahedral sites and CO oxidation catalytic activity for the first time. MgFe₂O₄, with particle size ranging from 8.1 nm to 190.0 nm, was prepared via a sol–gel method after post-annealing treatment at a temperature from 400 °C to 1000 °C. The growth of MgFe₂O₄ nanoparticles obeys the Ostwald ripening mechanism with the quantitative formula D⁵ = 2.08 × 10¹⁴t exp(−122.13/RT). The systematic characteristics show that the redox behavior and O₂ activation of hybrid catalysts of Pt/MgFe₂O₄-T rely on the grain size of MgFe₂O₄ nanoparticles. The Pt/MgFe₂O₄-500 catalyst with a support size of 20.6 nm exhibits a remarkable CO oxidation performance due to its abundant chemisorbed oxygen species on the surface and enhanced metal–support interactions among all examined catalysts. Our findings offer significant insight into the size-dependent structure, redox ability and oxygen activation properties of spinel materials and can greatly impact future exploration of novel materials in heterogeneous catalysis.