Unraveling the Transformation from Type-II to Z-Scheme in Perovskite-Based Heterostructures for Enhanced Photocatalytic CO₂ Reduction

Abstract

The ability to create perovskite-based heterostructures with desirable charge transfer characteristics represents an important endeavor to render a set of perovskite materials and devices with tunable optoelectronic properties. However, due to similar material selection and band alignment in type-II and Zscheme heterostructures, it remains challenging to obtain perovskite-based heterostructures with a favorable electron transfer pathway for photocatalysis. Herein, we report a robust tailoring of effective charge transfer pathway in perovskite-based heterostructures via a type-II to Z-scheme transformation for highly efficient and selective photocatalytic CO 2 reduction. Specifically, CsPbBr 3 /TiO 2 and CsPbBr 3 /Au/TiO 2 heterostructures are synthesized and then investigated by ultrafast spectroscopy. Moreover, taking CsPbBr 3 /TiO 2 and CsPbBr 3 /Au/TiO 2 as examples, operando experiments and theoretical calculations confirm that the type-II heterostructure could be readily transformed into a Zscheme heterostructure through establishing a low-resistance Ohmic contact, which indicates that a fast electron transfer pathway is crucial in Z-scheme construction, as further demonstrated by CsPbBr 3 /Ag/TiO 2 and CsPbBr 3 /MoS 2 heterostructures. In contrast to pristine CsPbBr 3 and CsPbBr 3 /TiO 2 , the CsPbBr 3 /Au/TiO 2 heterostructure exhibits 5.4-and 3.0-fold enhancement of electron consumption rate in photocatalytic CO 2 reduction. DFT calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy unveil that the superior CO selectivity is attributed to the lower energy of *CO desorption than that of hydrogenation to *HCO. This meticulous design sheds light on the modification of perovskite-based multifunctional materials and enlightens conscious optimization of semiconductor-based heterostructures with desirable charge transfer for catalysis and optoelectronic applications.

Modulating Adsorption–Redox Sites and Charge Separation of Cs3Bi2Br9–x@AgBr Core–Shell Heterostructure for Selective Toluene Photooxidation

“…The fast delay components (τ 1 and τ 2 ) are assigned to the quenching processes (electron diffusion and trap-assisted recombination), while the ultralong lifetime (τ 3 ) can be ascribed to the recombination of photoinduced electron–hole pairs. , Notably, compared with the τ 3 of pure Cs 3 Bi 2 Br 9 (4364 ps, relative amplitudes: 21.3%), that of Cs 3 Bi 2 Br 9– x @AgBr decays much faster and accounts for a lower proportion (1645 ps, 14%; see Figure d). This phenomenon suggests that the number of photogenerated electrons available for diffusion and recombination processes in Cs 3 Bi 2 Br 9 is reduced, which can be attributed to the transfer of electrons from CB of Cs 3 Bi 2 Br 9 to CB of AgBr after forming the Cs 3 Bi 2 Br 9– x @AgBr heterostructure. , Meantime, the extra negative peak at 523 nm (consistent with the E g of AgBr, 2.37 eV) in TA spectra of Cs 3 Bi 2 Br 9– x @AgBr corroborated the electron migration process. In addition, the weaker steady-state photoluminescence (PL, Figure S16) and shorter average PL lifetime (Figure e and Table S1) further declares that the recombination of photogenerated carriers of Cs 3 Bi 2 Br 9– x @AgBr is significantly suppressed.…”

Photocontrolled heterojunctions constructed from holmium single atom modified Mg1.2Ti1.8O5/g-C3N4 with enhanced photocatalytic CO2 conversion

“…In addition, the optimized MTO:Ho/CN:Ho exhibits better photocatalytic performance and excellent originality compared to other materials reported (Table S1, ESI†). 28–36 The mechanism of improved photocatalytic performance was studied by fully utilizing DFT calculations and various spectroscopic techniques such as steady-state, transient, and ultrafast absorption spectroscopy.…”

Perovskite Paradigm Shift: A Green Revolution with Lead-Free Alternatives in Photocatalytic CO2 Reduction

“…As a result, the efficiency of light-driven CO 2 reduction is still far from meeting large-scale industrial applications. Nonetheless, persistent efforts over the recent decades have been directed in this research pursuit, leading to commendable advancements in the field of photocatalytic CO 2 reduction. − To date, various photocatalysts have been developed for CO 2 reduction, including metal oxides, − sulfides, − metal–organic frameworks (MOFs), − carbon nitrides, − and perovskites. − Recently, halide perovskites have emerged as the burgeoning material for photocatalysis due to their outstanding optoelectronic properties such as tunable band structure, superior light-harvesting capability, high defect tolerance, and exceptional charge-transfer dynamics. − Halide perovskites have been actively explored as photocatalysts for CO 2 reduction especially in the recent years. ,− However, the most extensively studied halide perovskite, lead halide perovskite, is marred by a fatal flaw of toxicity attributed to the presence of lead. This poses serious environmental and health concerns, limiting its viable and safe utilization for practical applications …”