Inorganic Copper-Based Halide Perovskite for Efficient Photocatalytic CO2 Reduction

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.

Seeking environmentally friendly halide perovskite photocatalysts: synthesis, structure and photocatalytic performance exploration

Halide perovskites have high photoelectric conversion efficiency, making them promising candidates for photocatalysis. However, their toxic and unstable nature limits their applications. Here, we successfully synthesised three hybrid Bi-based halide perovskites: (HTMG)3Bi2Br9 (1), (HEI)2BiBr5 (2) and (HTMA)3Bi2Br9 (3). X-ray single-crystal diffraction analysis shows that they all contained 0D structures composed of isolated Bi-Br clusters. The three compounds showed excellent degradability and cycling stability for Sudan III dissolved in ethanol under simulated sunlight. In addition, the photocatalytic degradation performance of four Bi-based halide perovskites previously reported by our group is also characterised and summarised in this work.

Electronic Effect Promoted Visible-Light-Driven CO2-to-CO Conversion in a Water-Containing System

The design of unsaturated nonprecious metal complexes with high catalytic performance for photochemical CO2 reduction is still an important challenge. In this paper, four coordinatively unsaturated Co-salen complexes 1-4 were explored in situ using o-phenylenediamine derivatives and 5-methylsalicylaldehyde as precursors of the ligands in 1-4. It was found that complex 4, bearing a nitro substituent (-NO2) on the aromatic ring of the salen ligand, exhibits the highest photochemical performance for visible-light-driven CO2-to-CO conversion in a water-containing system, with TONCO and CO selectivity values of 5300 and 96%, respectively. DFT calculations and experimental results revealed that the promoted photocatalytic activity of 4 is ascribed to the electron-withdrawing effect of the nitro group in 4 compared to 1-3 (with -CH3, -F, and -H groups, respectively), resulting in a lower reduction potential of active metal centers CoII and lower barriers for CO2 coordination and C-O cleavage steps for 4 than those for catalysts 1-3.

In Situ Loading of Cu Nanocrystals on CsCuCl3 for Selective Photoreduction of CO2 to CH4

Rational design and facile synthesis of efficient environmentally friendly all-inorganic lead-free halide perovskite catalysts are of great significance in photocatalytic CO2 reduction. Aiming at photogenerated charge carrier separation and CO2 reaction dynamics, in this paper, a CsCuCl3 /Cu nanocrystals (NCs) heterojunction catalyst is designed and synthesized via a simple acid-etching solution process by using Cu2 O as the sacrificed template. Due to the disproportionation reaction of Cu2 O induced by concentrated hydrochloric acid, Cu NCs can be deposited onto the surface of CsCuCl3 microcrystals directly and tightly. As revealed by photoelectrochemical analysis, in situ Fourier transform infrared spectra, etc., the Cu NCs contribute a lot to extracting photoelectrons of CsCuCl3 to improve the charge separation efficiency, regulating the CO2 adsorption and activation, and also stabilizing the reaction intermediates. Therefore, CsCuCl3 /Cu heterojunction exhibits a total electron consumption rate of 58.77 µmol g-1 h-1 , which is 2.9-fold of that of single CsCuCl3 . Moreover, high CH4 selectivity of up to 92.7% is achieved, which is much higher than that of CsCuCl3 (50.4%) and most lead-free halide perovskite-based catalysts. This work provides an ingenious but simple strategy to rationally design cocatalysts in situ decorated perovskite catalysts for manipulating both the catalytic activity and the product selectivity.

Recent Advances and Opportunities of Eco-Friendly Ternary Copper Halides: A New Superstar in Optoelectronic Applications

Recently, the newly-emerging lead-free metal-halide materials with less toxicity and superior optoelectronic properties have received wide attention as the safer and potentially more robust alternatives to lead-based perovskite counterparts. Among them, ternary copper halides (TCHs) have become a vital group due to their unique features, including abundant structural diversity, ease of synthesis, unprecedented optoelectronic properties, high abundance, and low cost. Although the recent efforts in this field have made certain progresses, some scientific and technological issues still remain unresolved. Herein, a comprehensive and up-to-date overview of recent progress on the fundamental characteristics of TCH materials and their versatile applications is presented, which contains topics such as: i) crystal and electronic structure features and synthesis strategies; ii) mechanisms of self-trapped excitons, luminescence regulation, and environmental stability; and iii) their burgeoning optoelectronic devices of phosphor-converted white light-emitting diodes (WLEDs), electroluminescent LEDs, anti-counterfeiting, X-ray scintillators, photodetectors, sensors, and memristors. Finally, the current challenges together with future perspectives on the development of TCH materials and applications are also critically described, which is considered to be critical for accelerating the commercialization of these rapidly evolving technologies.

Self-supported CsPbBr3/Ti3C2Tx MXene aerogels towards efficient photocatalytic CO2 reduction

Aerogels, especially MXene aerogels, are an ideal multifunctional platform for developing efficient photocatalysts for CO₂ reduction because they are featured by abundant catalytic sites, high electrical conductivity, high gas absorption ability and self-supported structure. However, the pristine MXene aerogel has almost no ability to utilize light, which requires additional photosensitizers to assist it in achieving efficient light harvesting. Herein, we immobilized colloidal CsPbBr₃ nanocrystals (NCs) onto the self-supported Ti₃C₂T_x (where T_x represents surface terminations such as fluorine, oxygen, and hydroxyl groups) MXene aerogels for photocatalytic CO₂ reduction. The resultant CsPbBr₃/Ti₃C₂T_x MXene aerogels exhibit a remarkable photocatalytic activity toward CO₂ reduction with total electron consumption rate of 112.6 μmol g^-1h^-1, which is 6.6-fold higher than that of the pristine CsPbBr₃ NC powders. The improvement of the photocatalytic performance is presumably attributed to the strong light absorption, effective charge separation and CO₂ adsorption in the CsPbBr₃/Ti₃C₂T_x MXene aerogels. This work presents an effective perovskite-based photocatalyst in aerogel form and opens a new avenue for their solar-to-fuel conversions.

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.