Single-atom Pt-I3 sites on all-inorganic Cs2SnI6 perovskite for efficient photocatalytic hydrogen production

Abstract

Organic-inorganic lead halide perovskites are a new class of semiconductor materials with great potential in photocatalytic hydrogen production, however, their development is greatly plagued by their low photocatalytic activity, instability of organic component and lead toxicity in particular. Herein, we report an anti-dissolution environmentally friendly Cs₂SnI₆ perovskite anchored with a new class of atomically dispersed Pt-I₃ species (PtSA/Cs₂SnI₆) for achieving the highly efficient photocatalytic hydrogen production in HI aqueous solution at room temperature. Particularly, we discover that Cs₂SnI₆ in PtSA/Cs₂SnI₆ has a greatly enhanced tolerance towards HI aqueous solution, which is very important for achieving excellent photocatalytic stability in perovskite-based HI splitting system. Remarkably, the PtSA/Cs₂SnI₆ catalyst shows a superb photocatalytic activity for hydrogen production with a record turnover frequency of 70.6 h^-1 per Pt, about 176.5 times greater than that of Pt nanoparticles supported Cs₂SnI₆ perovskite, along with superior cycling durability. Charge-carrier dynamics studies in combination with theory calculations reveal that the dramatically boosted photocatalytic performance on PtSA/Cs₂SnI₆ originates from both unique coordination structure and electronic property of Pt-I₃ sites, and strong metal-support interaction effect that can not only greatly promote the charge separation and transfer, but also substantially reduce the energy barrier for hydrogen production. This work opens a new way for stimulating more research on perovskite composite materials for efficient hydrogen production.

Fig. 1. Energy band structure of Cs₂SnI₆ and its stability in aqueous HI solution system.

a Schematic diagram of preparation process for the PtSA/Cs₂SnI₆ catalyst. b SEM image and c PXRD pattern of Cs₂SnI₆. d Solubility of Cs₂SnI₆ in aqueous HI solution at different temperature. The inset shows the photograph of the 6 M HI aqueous solution with and without Cs₂SnI₆ powder at 25 °C. e PXRD patterns of precipitates for Cs₂SnI₆ powder in aqueous HI solution with various concentrations. f UV–visible absorption spectrum of Cs₂SnI₆ powder. The inset is the photograph of the Cs₂SnI₆. g Schematic energy band diagram of the Cs₂SnI₆, charge generation and charge transfer process over the Cs₂SnI₆ under visible-light irradiation.

Fig. 2. Structure characterization of PtSA/Cs₂SnI₆.

a Low-magnification and b high-magnification HAADF-STEM images, and c the corresponding STEM-EDS elemental mapping of PtSA/Cs₂SnI₆. d Pt L₃-edge XANES spectra and corresponding K³-weighted FT spectra at e R space and g k-space of PtSA/Cs₂SnI₆, PbI₂ and Pt foil. XANES f R space and h k-space fitting curves of PtSA/Cs₂SnI₆. i High-resolution XPS Pt 4f spectrum of PtSA/Cs₂SnI₆.

Fig. 3. Superior photocatalytic activity and stability of PtSA/Cs₂SnI₆ catalyst.

a The rate of photocatalytic H₂ evolution over PtSA/Cs₂SnI₆, PtNP/Cs₂SnI₆, and Cs₂SnI₆ catalysts. b TOF of PtSA/Cs₂SnI₆ and PtNP/Cs₂SnI₆ catalysts. c TOF comparisons of PtSA/Cs₂SnI₆ catalyst and other reported Pt-loaded halide perovskite photocatalysts. d Cyclic stability of the PtSA/Cs₂SnI₆ catalyst.

Fig. 4. Charge-carrier dynamics.

a Steady-state PL spectra, b time-resolved transient PL decay, c photocurrent responses spectra, and d electrochemical impedance spectroscopy of Cs₂SnI₆, PtNP/Cs₂SnI₆, and PtSA/Cs₂SnI₆ catalysts.

Fig. 5. Charge density distribution and Gibbs energy calculations.

The charge density difference maps between before and after photoexcitation: a PtNP/Cs₂SnI₆ and b PtSA/Cs₂SnI₆. The isosurface of charge density is 0.001e Å⁻³. The insets stand for the top view. The yellow region represents the additional electron distribution. An excess electron was added into the models, which was used to describe the photogenerated electron. c The PDOS (5d states) of PtNP/Cs₂SnI₆ and PtSA/Cs₂SnI₆. The dashed line stands for the Fermi level. d The calculated energy profile for hydrogen production on PtNP/Cs₂SnI₆ and PtSA/Cs₂SnI₆.