Amino Acid-Assisted Preparation of Homogeneous PbS/CsPbBr3 Nanocomposites for Enhanced Photoelectrocatalytic CO2 Reduction

Halide Perovskite Photocatalysts for Clean Fuel Production and Organic Synthesis: Opportunities and Challenges

The need to constrain the use of fossil fuels causing global warming is motivating the development of a variety of photocatalysts for solar-to-fuel generation and chemical synthesis. In particular, semiconductor-based photocatalysts have been extensively exploited in solar-driven organic synthesis, carbon dioxide (CO2) conversion into value-added products, and hydrogen (H2) generation from water (H2O) splitting. Recently, metal halide perovskites (MHPs) have emerged as an important class of semiconductors for heterogeneous photocatalysis owing to their interesting properties. Despite key issues with long-term stability and degradation in polar solvents due to their ionic character, there has been significant progress in halide perovskite-based photocatalysts with improving their stability and performance in the gas and liquid phases. This review discusses the state-of-the-art for using halide perovskite-based photocatalysts and photoelectrocatalysis in hydrogen production from water and halogen acid solutions, CO2 reduction into value-added chemicals, and various organic chemical transformations. The different types of halide perovskites used, design strategies to overcome the instability issues in polar solvents, and the efficiencies achieved are discussed. Furthermore, the outstanding challenges associated with the use of polar electrolytes and how the stability and performance can be improved are discussed.

Influence of Lewis basicity on the S2- induced synthesis of 0D Cs4PbBr6 hexagonal nanocrystals and its implications for optoelectronics

Perovskite nanocrystals (NCs) with their excellent optical and semiconductor properties have emerged as primary candidates for optoelectronic applications. While extensive research has been conducted on the 3D perovskite phase, the zero-dimensional (0D) form of this promising material in the NC format remains elusive. In this paper, a new synthesis strategy is proposed. According to the Hard-Soft Acid-Base (HSAB) principle, a novel class of hexagonal semiconductor nanocrystals (Cs4PbBr6 HNCs) derived from 0D perovskite Cs4PbBr6 is synthesized by doping an appropriate amount of PbS precursor solution into bromide. These Cs4PbBr6 HNCs are characterized and compared in detail to CsPbBr3 cubic nanocrystals (CsPbBr3 CNCs) as a reference. The Cs4PbBr6 HNCs exhibit significantly enhanced photoluminescence (PL) compared to CsPbBr3 CNCs, with an external quantum efficiency (EQE) reaching 24.19%. Furthermore, they demonstrate superior UV stability compared to CsPbBr3 CNCs. Comparative analysis of their physical properties and morphology, along with detailed investigations into band structures, density of states, and lifetime decay through DFT calculations, is provided. The practical application potential is validated by encapsulating them into backlight LEDs, covering 121.5% and 90.7% of the color gamut of NTSC and Rec. Our research provides comprehensive insights into the photophysical properties of inorganic halide perovskite nanomaterials and explores their potential in the field of optoelectronics.

Size Dependence of Ultrafast Electron Transfer from Didodecyl Dimethylammonium Bromide-Modified CsPbBr3 Nanocrystals to Electron Acceptors

Charge transfer efficiencies in all-inorganic lead halide perovskite nanocrystals (NCs) are crucial for applications in photovoltaics and photocatalysis. Herein, CsPbBr3 NCs with different sizes are synthesized by varying the ligand contents of didodecyl dimethylammonium bromide at room temperature. Adding benzoquinone (BQ) molecules leads to a decrease in the PL intensities and PL decay times in NCs. The electron transfer (ET) efficiency (ηET) increases with NC size in complexes of CsPbBr3 NCs and BQ molecules (NC-BQ complexes), when the same concentration of BQ is maintained, as investigated by transient photobleaching and photoluminescence spectroscopies. Controlling the same number of attached BQ acceptor molecules per NC induces the same ηET in NC-BQ complexes even though with different NC sizes. Our findings provide new insights into ultrafast charge transfer behaviors in perovskite NCs, which is important for designing efficient light energy conversion devices.

Recent Progress on Perovskite-Based Electrocatalysts for Efficient CO2 Reduction

An efficient carbon dioxide reduction reaction (CO2RR), which reduces CO2 to low-carbon fuels and high-value chemicals, is a promising approach for realizing the goal of carbon neutrality, for which effective but low-cost catalysts are critically important. Recently, many inorganic perovskite-based materials with tunable chemical compositions have been applied in the electrochemical CO2RR, which exhibited advanced catalytic performance. Therefore, a timely review of this progress, which has not been reported to date, is imperative. Herein, the physicochemical characteristics, fabrication methods and applications of inorganic perovskites and their derivatives in electrochemical CO2RR are systematically reviewed, with emphasis on the structural evolution and product selectivity of these electrocatalysts. What is more, the current challenges and future directions of perovskite-based materials regarding efficient CO2RR are proposed, to shed light on the further development of this prospective research area.

Photocatalytic CO2 Reduction Coupled with Oxidation of Benzyl Alcohol over CsPbBr3@PANI Nanocomposites

Herein, we successfully prepare conductive polyaniline (PANI)-encapsulated CsPbBr3 perovskite nanocrystals (PNCs) that demonstrate much improved photocatalytic performance and stability toward the CO2 reduction reaction (CRR) coupled with oxidation of benzyl alcohol (BA) to benzaldehyde. Due to the acid-base interaction between CO2 and PANI, CO2 molecules are selectively adsorbed on PANI in the form of carbamate. As a result, the rate of production of CO (rCO) reaches 26.1 μmol g-1 h-1 with a selectivity of 98.1%, which is in good agreement with the rate of oxidation (∼27.0 μmol g-1 h-1) of BA. Such a high reduction/oxidation rate is enabled by the fast electron transfer (∼2.2 ps) from PNCs to PANI, as revealed by femtosecond transient absorption spectroscopy. Moreover, because of the benefit of the encapsulation of PANI, no significant decrease in rCO is observed in a 10 h CRR test. This work offers insight into how to simultaneously achieve improved photocatalytic performance and stability of CsPbX3 PNCs.

In Situ Constructed Perovskite-Chalcogenide Heterojunction for Photocatalytic CO2 Reduction

Perovskite nanocrystals (PNCs) are promising candidates for solar-to-fuel conversions yet exhibit low photocatalytic activities mainly due to serious recombination of photogenerated charge carriers. Constructing heterojunction is regarded as an effective method to promote the separation of charge carriers in PNCs. However, the low interfacial quality and non-directional charge transfer in heterojunction lead to low charge transfer efficiency. Herein, a CsPbBr3 -CdZnS heterojunction is designed and prepared via an in situ hot-injection method for photocatalytic CO2 reduction. It is found that the high-quality interface in heterojunction and anisotropic charge transfer of CdZnS nanorods (NRs) enable efficient spatial separation of charge carriers in CsPbBr3 -CdZnS heterojunction. The CsPbBr3 -CdZnS heterojunction achieves a higher CO yield (55.8 µmol g-1  h-1 ) than that of the pristine CsPbBr3 NCs (13.9 µmol g-1  h-1 ). Furthermore, spectroscopic experiments and density functional theory (DFT) simulations further confirm that the suppressed recombination of charge carriers and lowered energy barrier for CO2 reduction contribute to the improved photocatalytic activity of the CsPbBr3 -CdZnS heterojunction. This work demonstrates a valid method to construct high-quality heterojunction with directional charge transfer for photocatalytic CO2 reduction. This study is expected to pave a new avenue to design perovskite-chalcogenide heterojunction.

Weakening Ligand-Liquid Affinity to Suppress the Desorption of Surface-Passivated Ligands from Perovskite Nanocrystals

The interfacial migration of surface-bound ligands highly affects the colloidal stability and optical quality of semiconductor nanocrystals, of which the underlying mechanism is not fully understood. Herein, colloidal CsPbBr₃ perovskite nanocrystals (PNCs) with fragile dynamic equilibrium of ligands are taken as the examples to reveal the important role of balancing ligand-solid/solvent affinity in suppressing the desorption of ligands. As a micellar surfactant, glycyrrhizic acid (GA) with bulky hydrophobic and hydrophilic groups exhibits a relatively smaller diffusion coefficient (∼440 μm²/s in methanol) and weaker ligand-liquid affinity than that of conventional alkyl amine and carboxy ligands. Consequently, hydrophilic GA-passivated PNCs (PNCs-GA) show excellent colloidal stability in various polar solvents with dielectric constant ranging from 2.2 to 32.6 and efficient photoluminescence with a quantum yield of 85.3%. Due to the suppressed desorption of GA, the morphological and optical properties of PNCs-GA are well maintained after five rounds purification and two months long-term storage. At last, hydrophilic PNCs-GA are successfully patterned through inkjet- and screen-printing technology. These findings offer deep insights into the interfacial chemistry of colloidal NCs and provide a universal strategy for preparing high-quality hydrophilic PNCs.