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<p>We report the first investigation of vacancy-ordered double perovskites Rb<sub>2</sub>OsX<sub>6</sub> (X = Cl, Br, I) as lead-free, aqueous-stable photocatalysts. Using accurate TB-mBJ + SOC DFT calculations, we predict direct band gaps tunable from 2.98&#xa0;eV (Cl) to 1.81&#xa0;eV (I), enabling the Br and I compounds to absorb ~ 43% of the solar spectrum with coefficients exceeding 10<sup>5</sup>&#xa0;cm⁻<sup>1</sup>. Band-edge positions straddle the water redox potentials in all three materials (CBM: − 0.05 to − 0.21&#xa0;V, VBM: + 1.63 to + 2.95&#xa0;V vs,. NHE at pH 0), satisfying the thermodynamic requirement for overall water splitting without external bias—the first achievement among lead-free A<sub>2</sub>BX<sub>6</sub> halide perovskites. Rb<sub>2</sub>O<sub>S</sub>I<sub>6</sub> further meets the thermodynamic threshold for CO<sub>2</sub> → CH<sub>4</sub> reduction. Ultra-low exciton binding energies, light effective masses (0.61–2.25&#xa0;m₀), and intrinsic aqueous stability conferred by the vacancy-ordered structure ensure efficient charge dynamics and durability, positioning Rb<sub>2</sub>OsX<sub>6</sub> as a breakthrough visible-light photocatalyst family.</p>

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From Sunlight to Fuels: Rb2OsX6 (X = Cl, Br, I) Perovskites Revolutionize Photocatalytic Hydrogen Generation

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Mohamed El Amine El Goutni,
  • Mohammed Batouche,
  • Hela Ferjani,
  • Taieb Seddik

摘要

We report the first investigation of vacancy-ordered double perovskites Rb2OsX6 (X = Cl, Br, I) as lead-free, aqueous-stable photocatalysts. Using accurate TB-mBJ + SOC DFT calculations, we predict direct band gaps tunable from 2.98 eV (Cl) to 1.81 eV (I), enabling the Br and I compounds to absorb ~ 43% of the solar spectrum with coefficients exceeding 105 cm⁻1. Band-edge positions straddle the water redox potentials in all three materials (CBM: − 0.05 to − 0.21 V, VBM: + 1.63 to + 2.95 V vs,. NHE at pH 0), satisfying the thermodynamic requirement for overall water splitting without external bias—the first achievement among lead-free A2BX6 halide perovskites. Rb2OSI6 further meets the thermodynamic threshold for CO2 → CH4 reduction. Ultra-low exciton binding energies, light effective masses (0.61–2.25 m₀), and intrinsic aqueous stability conferred by the vacancy-ordered structure ensure efficient charge dynamics and durability, positioning Rb2OsX6 as a breakthrough visible-light photocatalyst family.