Synthesis of sulfide-hydroxide layered materials modified with palladium and platinum and their photocatalytic activity in the reaction of indigo carmine reduction

Layered sulfide-hydroxide materials, analogues of the natural mineral valleriite, were synthesized at a temperature of 160 °C in an autoclave in the presence of nanosized palladium and platinum metal powders. The samples were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The obtained materials are composites consisting of valleriite phases and palladium sulfide or metallic platinum. The bandgap energy for the direct optical transition was estimated for the synthesized compounds, and the obtained values were in the range of 3.38–3.53 eV. The samples demonstrated positive effects in the model process of photocatalytic reduction of indigo carmine with sodium citrate compared to titanium(iv) oxide, single-phase valleriite, and nanosized palladium and platinum powders.