“…According to literature reports, most naturally occurring clay minerals contain a variety of metal ions, such as Fe II and Fe III , in their layer-structured frameworks due to the isomorphous substitution reactions with low valence transition-metal cations [54]. The contained iron species are effective mediators for a variety of reactions, such as the oxidation of aromatic compounds [55], the reduction of H 2 O 2 [56], the oxidation of ascorbic acid [57], and the photo-induced electron transfer across the clay|electro-lyte interface [58]. In view of this, we attribute the catalytic effect displayed by Mont.…”