Doping regulation of the electronic structure for halide double perovskite photocatalytic materials

Halide perovskites have garnered significant attention for their unique optoelectronic properties in solar-to-fuel conversions. However, the serious charge recombination and a lack of efficient active sites towards a low efficiency, and the poor stability in aqueous solution system limit the wide application of halide perovskite on photocatalysis.
In this presentation, we show our recent advancements on double halide perovskites at the aspects of optimization of the catalytic sites, promotion of the internal carrier separation, and development of water-stable photocatalytic materials. In case 1, the catalytic sites of Cs2AgBiCl6 (CABC) are regulated by doping Fe for efficient coupling of photocatalytic CO2 reduction and BA oxidation. The Fe-doped CABC (Fe: CABC) exhibits an enhanced visible-light response and effective charge separation. Experimental results and theoretical calculations reveal a synergistic interplay between Bi and Fe sites, where the Bi and Fe sites have lower activation energies toward CO2 reduction and BA oxidation. Further investigations demonstrate that electrons and holes prefer to accumulate at the Bi site and Fe site under light irradiation, respectively, which creates favourable conditions for facilitating CO2 reduction and BA oxidation.
In case 2, a rubidium (Rb) doped Cs2AgBiBr6 (Rb:CABB) hierarchical microsphere is developed for photocatalytic CO2 reduction. Experimental and theoretical analysis discloses that partially substituting Rb⁺ for Ag⁺ can effectively modulate the electronic structure of CABB, favoring charge separation and making adjacent Bi atoms an electron-rich active site. Further investigations indicated that Rb doping also reduces the energy barriers of the rate- determining step in CO2 reduction. As a result, Rb:CABB demonstrated an enhanced CO yield compared to its undoped counterpart.
In case 3, lead-free Cs2Pt0.25Sn0.75Br6 perovskites are reported for photocatalytic hydrogen reaction (HER) in water. The partial substitution of Sn atoms with Pt atoms dramatically enhances the HER performance and stability of the Cs2SnBr6 perovskites. This doping approach allows Cs2Pt0.25Sn0.75Br6 to work in the aqueous phase without saturated hydrohalic acid. Furthermore, the more negative formation energy and decreased surface hydrophilicity endow Cs2PtxSn1-xBr6 with a high stability against water.