Transformation of birnessite into hollandite under the influence of silver cations in aqueous medium

We report the formation and mechanism of silver hollandite by transformation from Na- or K- birnessite in hydrothermal conditions when 1 g birnessite reacts with 20 ml 0.08-0.1 M AgNO3 solutions for more than 0.5 h at above 300 °C. Silver hollandite show nanofiber crystals and mesoporous structure. The silver content entering in the birnessite plays a decisive role in the nature of products.199