# Study of Composite Photocatalysts Obtained by Photodeposition of Platinum on Layered Oxide HCa2Nb3O10 and Its Inorganic–Organic Hybrids

## TL;DR

This study explores where platinum is located in layered oxide materials used for photocatalysis and finds that platinum tends to be inside the material rather than on the surface.

## Contribution

The paper investigates the localization of platinum in layered oxides and introduces a novel method using aqua regia etching to determine its stability and distribution.

## Key findings

- Less than 20% of platinum is located on the surface of HCa2Nb3O10.
- Platinum in amine-intercalated HCa2Nb3O10 is more stable against aqua regia treatment.
- Intercalation with amines reduces surface platinum attachment.

## Abstract

In recent decades, layered perovskite-like oxides have been intensively investigated as prominent photocatalysts for water splitting as a method of hydrogen production. In many previous papers, it was shown that deposition of platinum on an oxide sample dramatically increases photocatalytic activity. Nevertheless, little research was conducted to reveal the localisation of platinum in layered oxides; either it is located on the surface or in the interlayer space. In the present work, an attempt to answer this question is made. An HCa2Nb3O10 layered perovskite-like oxide was modified with platinum by photoreduction of H2PtCl6 and then was intercalated with n-alkylamines (R = Me, Bu, Oc). Moreover, another set of samples were prepared by intercalating the amines first into HCa2Nb3O10, followed by Pt deposition. Besides conventional methods for sample characterisation, we measured the kinetics of Pt dissolution during aqua regia etching of the samples, hoping that the rate of platinum dissolution would provide some information about its localisation. It was shown that in HCa2Nb3O10 modified with platinum, less than 20% of the platinum is located on the surface, and that in the case of HCa2Nb3O10 intercalated with amines, an even smaller amount of platinum attaches to the surface. Moreover, Pt in HCa2Nb3O10 intercalated with amines was found to be significantly more stable against aqua regia treatment than in HCa2Nb3O10 decorated with platinum directly.