“…The reactivity of PEO layers can be easily influenced by changing the composition of the electrolytic bath, which is usually completed by adding soluble ions of dopants, i.e., Ni and Cu, to the electrolytic bath to prepare catalytic materials for CO to CO 2 oxidation [ 27 , 28 , 29 ], photoactive materials [ 26 , 30 , 31 ], biomaterials with possible antibacterial properties [ 32 , 33 ] or even catalysts for desulphurization and denitrification [ 34 ]. Other methods of doping of PEO layers are the impregnation of the coating with the soluble salt of the dopant, followed by drying and air annealing (500–1050 °C) [ 29 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], the hydrothermal route [ 43 , 44 ], electrodeposition [ 45 , 46 ], the sol-gel method [ 47 ], electroless plating [ 48 ], the solid-state reaction method [ 49 ], the alcohol-thermal method [ 50 ], reactive magnetron co-sputtering [ 51 ], dip coating [ 52 ] or even the coating of different materials with a TiO 2 paste [ 53 ]. A different approach is the preparation of an electrolytic bath in suspension [ 18 , 54 , 55 , 56 ].…”