La doping of CoFe Prussian blue analogs for improved catalytic activity toward norfloxacin degradation

Abstract

Prussian blue analogs (PBAs) are promising catalysts in heterogeneous oxidation processes. The catalytic activity of PBAs relies on exposed crystal facets and accessible active sites on the PBA framework. Employing a heteroatom doping strategy using a rare earth element (La), we regulated the crystal structure and optimized the catalytic activity of CoFe PBA for peroxymonosulfate (PMS)-driven degradation of the antibiotic norfloxacin (NOR). The La atoms were mainly doped in the interstitial sites of the CoFe PBA cubic lattices, without affecting the electron distributions of Co and Fe metals or the face-centered cubic crystal phase of the coordination skeleton. La doping dominated the (111) and (100) as the main exposed facets of CoFeLa PBA, increasing the affinity of CoFeLa PBAs for PMS adsorption due to the higher surface energy of the two facets. Consequently, the activation energy considerably declined from 77.57 kJ/mol in CoFe PBA to 51.66 kJ/mol in CoFeLa PBA and the catalytic activity for PMS-driven NOR degradation was largely improved, which can reach 76.4 % removal of NOR within 15 min, with an increased initial rate constant k of 0.095 min−1. 1O2 was proven as the main reactive specie responsible for NOR degradation in the PMS/CoFeLa system, and O2·− and SO4·− were verified as the important intermediates to generate 1O2. Thus, La doping can effectively enhance the catalytic performance of PBA-based catalysts for organic pollutant removal.