Unassisted HI photoelectrolysis using n-WSe2 solar absorbers

Cs3Bi2I9 nanodiscs with phase and Bi(III) state stability under reductive potential or illumination for H2 generation from diluted aqueous HI

The increasingly popular, lead-free perovskite, Cs₃Bi₂I₉ has a vulnerable Bi³⁺ state under reductive potentials, due to the high standard reduction potential of Bi³⁺/Bi^δ+ (0 < δ < 3). Contrary to this fundamental understanding, herein, ligand-coated Cs₃Bi₂I₉ nanodiscs (NDs) demonstrate outstanding electrochemical stability with up to -1 V versus a saturated calomel electrode in aqueous 0.63 M (5% v/v) and 6.34 M (50% v/v) hydroiodic acid (HI), with a minor BiI₃ fraction due to the unavoidable partial aqueous disintegration of the perovskite phase after 8 and 16 h, respectively. A dynamic equilibrium of saturated 0.005 M NDs maintains the common ion effect of I^-, and remarkably stabilizes ∼93% Bi³⁺ in 0.63 M HI under a strong reductive potential. In comparison, the hexagonal phase of bulk Cs₃Bi₂I₉ disintegrates considerably in the semi-aqueous media. Lowering the concentration of synthetic HI from the commonly used ∼50% v/v by elevating the pH from -0.8 to 0.2 helps in reducing the cost per unit of H₂ production. Our Cs₃Bi₂I₉ NDs with a hexagonal lattice have 4-6 (002) planes stacked along the c-axis. With 0.005 M photostable NDs, 22.5 μmol h^-1 H₂ is photochemically obtained within 8 h in a 6.34 M HI solution. Electrocatalytic H₂ evolution occurs with a turnover frequency of 11.7 H₂ per s at -533 mV and outstanding operational stability for more than 20 h.

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

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⁻¹per 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.

Organic-inorganic lead halide perovskites are a new class of photocatalysts, however, instability and toxicity pose challenges. Here, the authors report a non-toxic all-inorganic Cs₂SnI₆ perovskite anchored with atomically dispersed Pt-I₃ for efficient photocatalytic hydrogen production in hydrogen iodide solution.

The effects of nonmetal dopants on the electronic, optical, and catalytic performances of monolayer WSe2 by a first-principles study

Doping modifies the electronic, optical, and catalytic behavior of materials through the newly formed chemical bonds and the localized electrons.