Engineering Semi-Reversed Quantum Well Photocatalysts for Highly-Efficient Solar-to-Fuels Conversion

Customized Ultrathin Oxygen Vacancy-Rich Bi2W0.2Mo0.8O6 Nanosheets Enabling a Stepwise Charge Separation Relay and Exposure of Lewis Acid Sites toward Broad-Spectrum Photothermal Catalysis

Designing robust photocatalysts with broad light absorption, effective charge separation, and sufficient reactive sites is critical for achieving efficient solar energy conversion. However, realizing these aims simultaneously through a single material modulation approach poses a challenge. Here, a 2D ultrathin oxygen vacancy (Ov)-rich Bi2W0.2Mo0.8O6 solid solution photocatalyst is designed and fabricated to tackle the dilemma through component and structure optimization. Specifically, the construction of a solid solution with ultrathin structure initially facilitates the separation of photoinduced electron-hole pairs, while the introduction of Ov strengthens such separation. In the meantime, the presence of Ov extends light absorption to the NIR region, triggering a photothermal effect that further enhances the charge separation and accelerates the redox reaction. As such, photoinduced charge carriers in the Ov-Bi2W0.2Mo0.8O6 are separated step by step via the synergistic action of 2D solid solution, OV, and solar heating. Furthermore, the introduction of OV exposes surface metal sites that serve as reactive Lewis acid sites, promoting the adsorption and activation of toluene. Consequently, the designed Ov-Bi2W0.2Mo0.8O6 reveals an enhanced photothermal catalytic toluene oxidation rate of 2445 µmol g-1 h-1 under a wide spectrum without extra heat input. The performance is 9.0 and 3.9 times that of Bi2WO6 and Bi2MoO6 nanosheets, respectively.

All-Inorganic Perovskite NiTiO3/Cs3Sb2I9 Heterostructure for Photocatalytic CO2 Reduction to CH4 with High Selectivity

Developing efficient and stable halide perovskite-based photocatalysts for highly selectivity reduction CO2 to valuable fuels remains a significant challenge due to their intrinsic instability. Herein, a novel heterostructure featuring 2D Cs3Sb2I9 nanosheets on a 3D flower-like mesoporous NiTiO3 framework using a top-down stepwise membrane fabrication technique is constructed. The unique bilayer heterostructure formed on the 3D mesoporous framework endowed NiTiO3/Cs3Sb2I9 with sufficient and close interface contact, minimizing charge transport distance, and effectively promoting the charge transfer at the interface, thus improving the reaction efficiency of the catalyst surface. As revealed by characterization and calculation, the coupling of Cs3Sb2I9 with NiTiO3 facilitates the hydrogenation process during catalytic, directing reaction intermediates toward highly selective CH4 production. Furthermore, the van der Waals forces inherent in the 3D/2D heterostructure with face-to-face contact provide superior stability, ensuring the efficient realization of photocatalytic CO2 reduction to CH4. Consequently, the optimized 3D/2D NiTiO3/Cs3Sb2I9 heterostructure demonstrates an impressive CH4 yield of 43.4 µmol g-1 h-1 with a selectivity of up to 88.6%, surpassing most reported perovskite-based photocatalysts to date. This investigation contributes to overcoming the challenges of commercializing perovskite-based photocatalysts and paves the way for the development of sustainable and efficient CO2 conversion technologies.