Optimization of Methods for Synthesis and Protonation of Layered Perovskite-Structured Photocatalysts APb2Nb3O10 (A = Rb, Cs)

Synthesis of layered perovskite-like niobates APb(2)Nb(3)O(10) (A = Rb, Cs), being promising visible light active photocatalysts, has been conducted by the ceramic method under variable conditions to obtain the samples with the highest possible phase purity. The oxides prepared were shown practically not to undergo protonation and hydration of the interlayer space upon keeping in water. Both phases APb(2)Nb(3)O(10) were used to yield corresponding protonated hydrated forms H(x)A(1 - x)Pb(2)Nb(3)O(10)center dot yH(2)O via acid treatment. It was found that the propensity of the samples to the substitution of interlayer cations by protons depends clearly on the A(+) cation: while the Rb-containing niobate is capable of complete protonation (x = 1) upon a single treatment with 6 M nitric acid, the Cs-containing counterpart gives a high enough protonation degree (x >= 0.9) only after several renewals of the acid solution. The protonated niobates obtained were exposed to an additional water treatment under hydrothermal conditions, which allowed producing new hydrated derivatives with the enhanced thermal stability towards interlayer dehydration as compared with the protonated precursors.

Automated summary

Layered perovskite-like niobates APb(2)Nb(3)O(10) (A = Rb, Cs) were synthesized by the ceramic method. The oxides showed resistance to protonation and hydration in water. Acid treatment of the oxides yielded protonated hydrated forms H(x)A(1 - x)Pb(2)Nb(3)O(10)center dot yH(2)O. The propensity of the samples to protonation depended on the A(+) cation, with the Rb-containing niobate capable of complete protonation while the Cs-containing counterpart required multiple acid treatments. Protonated niobates showed enhanced thermal stability towards interlayer dehydration after aqueous treatment under hydrothermal conditions.