Perovskite-based Ca-Ni-Fe oxides for azo pollutants fast abatement through dark catalysis

Dark heterogeneous catalysis dismisses the need for both light and additional chemicals, and it also complements or even replaces more traditional pollutant abatement processes. Although recently reported, dark catalysts take several hours to bring the pollutant concentration to under 50 %, tested just with low weight pollutants, and their structural-mechanism relations have remained uncharacterized. Therefore, calcium nickel-iron mixed oxides (CNF) based catalysts, synthesized targeting CaNixFe(1-x)O3-delta, are here introduced. The oxides mixture demonstrated (under 50 % after 5 min) to be effective and fast on the degradation of several pollutants under dark conditions, without the addition of reagents or energy/light irradiation, degradation attributed mainly to Ni-doped Ca2Fe2O5. The active species analysis revealed a reaction scheme initiated by the contact pollutant-catalyst, followed by the pollutant molecule's breakdown, following the generation of hydroxyl radicals, electrons, singlet oxygen, and electrons/holes hopping within the material. It is anticipated that this work will inspire the future design of this sort of catalyst.