Efficient carbon dioxide conversion by nickel ferrite-based catalysts derived from metallurgical electroplating sludge collaborating with low-temperature plasma.

An innovative, environment-friendly, and efficient method was proposed for the synergistic low-temperature plasma conversion of CO by using nickel ferrite (NiFeO) catalyst. NiFeO, characterised by a mesoporous spinel structure, was successfully synthesised from electroplating sludge by a single-step heat treatment. The catalyst was uniformly distributed with SiO glass beads throughout the plasma discharge area, enabling an efficient transition from single filament to filament-surface coupled discharge. The outcomes were a 39.02 % increase in discharge charge and a 15 % increase in output power compared with plasma-only situation. CO-conversion optimisation tests showed the formation of a 'microreaction zone' enhanced the development of gas vortices and turbulence, promoting the CO-conversion ratio, CO generation ratio, and energy efficiency to 20.64 %, 15.74 %, and 1.864 %, respectively, under the NiFeO catalyst-facilitated low-temperature plasma conditions. The conversion route involved generating excited-state CO, O, and electrons through plasma ionisation of CO, alongside the creation of oxygen vacancies (V). These vacancies regenerated by consuming lattice oxygen (O), facilitating CO convert to CO and O by electrons. Furthermore, the catalysts offered sites for adsorbing reaction intermediates, which further facilitated CO dissociation and product formation. The Fe and Ni ions in the NiFeO catalyst reacted by redox to produce O and V and maintain charge equilibrium. This study demonstrated that the NiFeO catalyst and synergistic plasma effectively converted CO whilst reducing the reaction's energy barrier, thereby providing theoretical support for improved CO utilisation as a resource.