Lead-Free Cs2TeX6 (X = Cl, Br, and I) Perovskite Microcrystals with High Stability for Efficient Photocatalytic CO2 Reduction

Unveiling Dynamic Structure and Bond Evolutions in BiOIO3 Photocatalysts during CO2 Reduction

We have established a correlation between photocatalytic activity and dynamic structure/bond evolutions of BiOIO3-based photocatalysts during CO2 reduction by combining operando X-ray diffraction with photoelectron spectroscopy. More specifically, the selective photo-deposition of PtOx species on BiOIO3 (010) facets could effectively promote the electron enrichment on Bi active sites of (100) facets for facilitating the adsorption/activation of CO2 molecules, leading to the formation of Bi sites with high oxidation state and the shrink of crystalline structures. With introducing light irradiation to drive CO2 reduction, the Bi active sites with high oxidation states transformed into normal Bi3+ state, accompanying with the expansion of crystalline structures. Owing to the dynamic structure, bond, and chemical-state evolutions, a significant improvement of photocatalytic activity for CO evolution has been achieved on PtOx-BiOIO3 (195.0 μmol g-1 ⋅ h-1), much higher than the pristine (61.9 μmol g-1 ⋅ h-1) as well as metal-Pt decorated BiOIO3 (70.3 μmol g-1 ⋅ h-1) samples. This work provides new insights to correlate the intrinsically dynamic structure/bond evolutions with CO2 reduction activity, which may help to guide future photocatalyst design.

Structural Modification Strategies, Interfacial Charge-Carrier Dynamics, and Solar Energy Conversion Applications of Organic-Inorganic Halide Perovskite Photocatalysts

Over the past few decades, organic-inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air-water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge-carrier transfer and the enlargement of long-term stability, are elucidated. Subsequently, the interfacial mechanisms and charge-carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time-resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter.

Copper Modulated Lead-Free Cs4 MnSb2 Cl12 Double Perovskite Microcrystals for Photocatalytic Reduction of CO2

In order to deal with the global energy crisis and environmental problems, reducing carbon dioxide through artificial photosynthesis has become a hot topic. Lead halide perovskite is attracted people's attention because of its excellent photoelectric properties, but the toxicity and long-term instability prompt people to search for new photocatalysts. Herein, a series of <111> inorganic double perovskites Cs4 Mn1-x Cux Sb2 Cl12 microcrystals (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) are synthesized and characterized. Among them, Cs4 Mn0.7 Cu0.3 Sb2 Cl12 microcrystals have the best photocatalytic performance, and the yields of CO and CH4 are 503.86 and 68.35 µmol g-1 , respectively, after 3 h irradiation, which are the highest among pure phase perovskites reported so far. In addition, in situ Fourier transform infrared (FT-IR) spectroscopy and electron spin resonance (ESR) spectroscopy are used to explore the mechanism of the photocatalytic reaction. The results highlight the potential of this class of materials for photocatalytic reduction reactions.

Subnanometric Bismuth Clusters Confined in Pyrochlore-Bi2 Sn2 O7 Enable Remarkable CO2 Photoreduction

The development of highly efficient photocatalysts for conversion of carbon dioxide (CO2 ) with water (H2 O) into chemical fuels is of great importance for energy sustainability and carbon resource utilization. Herein, we demonstrated a facile hydrothermal method for in situ construction of subnanometric Bi metallic clusters in pyrochlore-Bi2 Sn2 O7 frameworks, leading to the remarkable improvements of photocatalytic performances for CO2 reduction into CO in the absence of sacrificial reagent. More specifically, an outstanding CO evolution activity of 114.1 μmol g-1  h-1 has been achieved, more than 20-fold improvement compared with the pristine Bi2 Sn2 O7 (5.7 μmol g-1  h-1 ). Detailed experiments together with in situ characterizations reveal that the spatially confined Bi clusters could significantly promote charge-separation/electron-enrichment and adsorption/activation of CO2 molecules, which provides highly efficient reaction channels to facilitate the generation of *COOH intermediate as well as the subsequent desorption of *CO towards CO formation. These demonstrations provide an important knowledge for precise design and fabrication of highly efficient photocatalysts for CO2 conversion into solar fuels.

Recent Advances and Future Perspectives of Lead-Free Halide Perovskites for Photocatalytic CO2 Reduction

It is still challenging to design and develop the state-of-the-art photocatalysts toward CO2 photoreduction. Enormous researchers have focused on the halide perovskites in the photocatalytic field for CO2 photoreduction, due to their excellent optical and physical properties. The toxicity of lead-based halide perovskites prevents their large-scale applications in photocatalytic fields. In consequence, lead-free halide perovskites (LFHPs) without the toxicity become the promising alternatives in the photocatalytic application for CO2 photoreduction. In recent years, the rapid advances of LFHPs have offer new chances for the photocatalytic CO2 reduction of LFHPs. In this review, we summarize not only the structures and properties of A2 BX6 , A2 B(I)B(III)X6 , and A3 B2 X9 -type LFHPs but also their recent progresses on the photocatalytic CO2 reduction. Furthermore, we also point out the opportunities and perspectives to research LFHPs photocatalysts for CO2 photoreduction in the future.

Novelty All-Inorganic Titanium-Based Halide Perovskite for Highly Efficient Photocatalytic CO2 Conversion

Lead halide perovskite materials have great potential for photocatalytic reaction due to their low fabrication cost, unique optical absorption coefficient, and suitable band structures. However, the main problems are the toxicity and instability of the lead halide perovskite materials. Therefore, a facile synthetic method is used to prepare lead-free environmentally friendly Cs₂ TiX₆ (X = Cl, Cl_0.5 Br_0.5 , Br) perovskite materials. Their structural and optical characteristics are systematically investigated. The band gaps of the produced samples are illustrated to be from 1.87 to 2.73 eV. Moreover, these materials can keep high stability in harsh environments such as illumination and heating, and the Cs₂ Ti(Cl_0.5 Br_0.5 )₆ microcrystals demonstrate the yields of 176 µmol g^-1 for CO and 78.9 µmol g^-1 for CH₄ after light irradiation for 3 h, which is of the first report of Ti-based perovskite photocatalysts. This finding demonstrates that the Ti-based perovskites will create opportunities for photocatalytic applications, which may offer a new idea to construct low-cost, eco-friendly, and bio-friendly photocatalysts.