# Efficient and Stable Hydrogen Evolution from HI Splitting Using a Robust 2D Tin-Iodide Perovskite

## TL;DR

A new tin-iodide perovskite material efficiently produces hydrogen from sunlight and is highly stable and recyclable.

## Contribution

A 2D tin-iodide perovskite with exceptional photostability and recoverability is developed for hydrogen production.

## Key findings

- 4FPSI perovskite microcrystals show long-term photostability and sustained H2 production from HI splitting.
- Intermittent light irradiation enhances H2 production by improving charge separation and reducing recombination.
- Degraded materials can be chemically recovered to restore hydrogen production capabilities.

## Abstract

Photocatalytic hydrogen (H2) production with
2D Ruddlesden–Popper
tin-iodide perovskites has recently emerged as a promising route toward
sustainable solar-to-fuel conversion. However, a major limitation
of these systems lies in their rapid degradation caused by tin and
iodide oxidation. In the present study, we report the synthesis of
4-fluorophenethylammonium tin-iodide (4FPSI) perovskite microcrystals
in a mixture of hydroiodic acid (HI) and H2O, which exhibit
remarkable long-term photostability and sustained photocatalytic H2 production via HI splitting. Intermittent light irradiation
was shown to further boost H2 production by promoting efficient
charge separation and suppressing the accumulation of trapped charge
carriers that drive recombination. Notably, reused and aged materials
showed enhanced photocatalytic performance, which theoretical simulations
attributed to surface reconstruction that exposes additional tin catalytic
active sites. The samples that underwent degradation after multiple
photocatalytic tests could be recovered through a simple chemical
treatment and restore the H2 production capability. Together,
these findings highlight tin-iodide perovskites as highly promising
photocatalysts for solar H2 production, combining durability,
recyclability, and facile recovery strategies to simultaneously advance
all key performance metrics.