“…[ 5 , 22 ] The complex EPR spectrum of a‐TiO 2 ‐Cu SA ( Figure 2 a ) consists of five components, as determined by computer simulations. The magnetic parameters of the main constituent (≈85%), denoted as Cu‐1, are as follows: g || ≅ 2.353, A || ≅ 113 G, and g ⊥ ≅ 2.067, with an unresolved perpendicular hyperfine structure (HFS) typical of surface‐bound single Cu(II) ions ( d 9 electronic configuration) [ 5 , 23 ] or Cu(II) ions substituting lattice Ti(IV), [ 6 , 24 ] both expected to be spectroscopically the same. The next two components, Cu‐2 (≈13%, g || ≅ 2.354, A || ≅ 114 G and g ⊥ ≅ 2.065, A ⊥ ≅ 8 G) and Cu‐3 (∼2%, g || ≅ 2.353, A || ≅ 114 G and g ⊥ ≅ 2.050, A ⊥ ≅ 23 G), can also be undoubtedly assigned to isolated copper centers in slightly different environments.…”