All-inorganic perovskite/graphitic carbon nitride composites for CO2 photoreduction into C1 compounds under low concentrations of CO2

Efficient reduction of CO2 and inhibition of hydrogen precipitation by polyoxometalate photocatalyst modified with the metal Mn

Photocatalytic reduction of CO2 to chemical fuels is attractive for solving both the greenhouse effect and the energy crisis, but the key challenge is to design and synthesize photocatalysts with remarkable performance under visible light irradiation. Efficient catalytic carbon dioxide reduction (CO2RR) with light is considered a promising sustainable and clean approach to solve environmental problems. Herein, we found a new photocatalyst ([Mn(en)2]6[V12B18O54(OH)6]) (abbreviated as Mn6V12) based on the modifiability of polyoxometalates, in which Mn acts as a modifying unit to efficiently reduce CO2 to CO and effectively inhibit the hydrogen precipitation reaction. This Mn modified polyoxometalate catalyst has a maximum CO generation rate of 4625.0 μmol g-1 h-1 and a maximum H2 generation rate of 499.6 μmol g-1 h-1, with a selectivity of 90.3% for CO generation and 9.7% for H2 generation. This polyoxometalate photocatalyst can effectively reduce CO and inhibit the hydrogen precipitation reaction. It provides a new idea for the efficient photocatalytic carbon dioxide reduction (CO2RR) with polyoxometalate catalysts.

A Targeted Review of Current Progress, Challenges and Future Perspective of g-C3 N4 based Hybrid Photocatalyst Toward Multidimensional Applications

The increasing demand for searching highly efficient and robust technologies in the context of sustainable energy production totally rely onto the cost-effective energy efficient production technologies. Solar power technology in this regard will perceived to be extensively employed in a variety of ways in the future ahead, in terms of the combustion of petroleum-based pollutants, CO₂ reduction, heterogeneous photocatalysis, as well as the formation of unlimited and sustainable hydrogen gas production. Semiconductor-based photocatalysis is regarded as potentially sustainable solution in this context. g-C₃ N₄ is classified as non-metallic semiconductor to overcome this energy demand and enviromental challenges, because of its superior electronic configuration, which has a median band energy of around 2.7 eV, strong photocatalytic stability, and higher light performance. The photocatalytic performance of g-C₃ N₄ is perceived to be inadequate, owing to its small surface area along with high rate of charge recombination. However, various synthetic strategies were applied in order to incorporate g-C₃ N₄ with different guest materials to increase photocatalytic performance. After these fabrication approaches, the photocatalytic activity was enhanced owing to generation of photoinduced electrons and holes, by improving light absorption ability, and boosting surface area, which provides more space for photocatalytic reaction. In this review, various metals, non-metals, metals oxide, sulfides, and ferrites have been integrated with g-C₃ N₄ to form mono, bimetallic, heterojunction, Z-scheme, and S-scheme-based materials for boosting performance. Also, different varieties of g-C₃ N₄ were utilized for different aspects of photocatalytic application i. e., water reduction, water oxidation, CO₂ reduction, and photodegradation of dye pollutants, etc. As a consequence, we have assembled a summary of the latest g-C₃ N₄ based materials, their uses in solar energy adaption, and proper management of the environment. This research will further well explain the detail of the mechanism of all these photocatalytic processes for the next steps, as well as the age number of new insights in order to overcome the current challenges.

Facets-Directed Epitaxially Grown Lead Halide Perovskite-Sulfobromide Nanocrystal Heterostructures and Their Improved Photocatalytic Activity

Lead halide perovskite nanocrystal heterostructures have been extensively studied in the recent past for improving their photogenerated charge carriers mobility. However, most of such heterostructures are formed with random connections without having strong evidence of epitaxial relation. Perovskite-chalcohalides are the first in this category, where all-inorganic heterostructures are formed with epitaxial growth. Going beyond one facet, herein, different polyhedral nanocrystals of CsPbBr₃ are explored for facet-selective secondary epitaxial sulfobromide growths. Following a decoupled synthesis process, the heterojunctions are selectively established along {110} as well as {200} facets of 26-faceted rhombicuboctahedrons, the {110} facets of armed hexapods, and the {002} facets of 12-faceted dodecahedron nanocrystals of orthorhombic CsPbBr₃. Lattice matching induced these epitaxial growths, and their heterojunctions have been extensively studied with electron microscopic imaging. Unfortunately, these heterostructures did not retain the intense host emission because of their indirect band structures, but such combinations are found to be ideal for promoting photocatalytic CO₂ reduction. The pseudo-Type-II combination helped here in the successful movement of charge carriers and also improved the rate of catalysis. These results suggest that facet-selective all-inorganic perovskite heterostructures can be epitaxially grown and this could help in improving their catalytic activities.

2D/2D CsPbBr3/BiOCl Heterojunction with an S-Scheme Charge Transfer for Boosting the Photocatalytic Conversion of CO2

The rational design of a two-dimensional (2D)/2D "face-to-face" heterojunction photocatalyst is crucial for the mediation of interfacial charge transfer/separation. Herein, a unique 2D/2D step-scheme (S-scheme) photocatalyst of CsPbBr₃/BiOCl is constructed by the self-assembly of CsPbBr₃ and BiOCl nanosheets (NSs). Profiting from the effective interface contact and appropriate band structures between CsPbBr₃ and BiOCl NSs, a valid S-scheme heterojunction of CsPbBr₃/BiOCl is established. Density functional theory (DFT) calculations and a series of characterization techniques including X-ray photoelectron spectra (XPS), photoassisted Kelvin probe force microscopy (KPFM), and electron spin resonance (ESR) systematically corroborate the S-scheme charge-transfer mechanism between CsPbBr₃ and BiOCl. The formation of an S-scheme heterojunction endows the photocatalyst with boosted charge separation and retainment of the highest redox ability. As a result, the obtained 2D/2D CsPbBr₃/BiOCl S-scheme photocatalyst shows much superior CO₂-reduction performance to single CsPbBr₃ and BiOCl. This investigation provides new insights into the construction of novel S-scheme heterojunctions based on 2D/2D photocatalytic systems.

Step-Scheme Photocatalyst of CsPbBr3 Quantum Dots/BiOBr Nanosheets for Efficient CO2 Photoreduction

Heterojunction manipulation has been deemed as a promising approach in exploring efficient photocatalysts for CO₂ reduction. In this article, a novel step-scheme (S-scheme) photocatalyst of CsPbBr₃ quantum dots/BiOBr nanosheets (CPB/BiOBr) was fabricated via a facile self-assembly process. The strong interaction, staggered energy band alignments, and much different Fermi levels between CsPbBr₃ and BiOBr promised the formation of an S-scheme heterojunction. The resultant CPB/BiOBr heterojunction delivered remarkable photocatalytic performance in CO₂ reduction, with an electron consumption rate of 72.3 μmol g^-1 h^-1, which was 4.1 and 5.7 times that of single CsPbBr₃ and BiOBr, respectively. The superior photocatalytic performance originated from the impactful spatial separation of photoinduced electron-hole pairs, as well as the preservation of strongly reductive electrons for CO₂ reduction. This work offers a rational strategy to design S-scheme heterojunctions based on lead halide perovskites, which are expected to have potential applications in the field of photocatalysis and solar energy utilization.

Assembling an Affinal 0D CsPbBr3/2D CsPb2Br5 Architecture by Synchronously In Situ Growing CsPbBr3 QDs and CsPb2Br5 Nanosheets: Enhanced Activity and Reusability for Photocatalytic CO2 Reduction

Conversion of CO₂ into valuable chemical feedstocks through artificial photosynthesis is an effective strategy to alleviate energy and environmental issues. Herein, we have developed a novel perovskite-based catalyst via in situ growing CsPbBr₃ quantum dots (QDs) on the affinal 2D CsPb₂Br₅ nanosheets for CO₂ photoconversion. CsPbBr₃ QDs were generated by peeling off layers from their cubic counterpart; meanwhile, CsPb₂Br₅ nanosheets were formed by heaping up the peeled layers. The resultant dual-phase composite exhibited outstanding activity and selectivity for photocatalytic conversion of gaseous CO₂ with a CO generation rate of 197.11 μmol g^-1 h^-1 under 300 W Xe lamp irradiation, which is 2.5 and 1.1 times higher than that of pure CsPb₂Br₅ or CsPbBr₃. Importantly, the fabricated dual-phase material presented extremely high stability and was able to maintain an unchangeable CO₂ conversion rate under wet air in the consecutive 10 h of recycling test. Furthermore, attributing to the in situ assembling strategy, the close contact allowed photo-generated electrons in CsPbBr₃ QDs to transfer rapidly to CsPb₂Br₅, and the affluent active sites in such an architecture enabled achieving enhanced CO₂ photoconversion activity. The present work provides an attractive approach for in situ constructing a consubstantial perovskite-based composite photocatalyst to ensure great stability and excellent activity for artificial photocatalytic CO₂ conversion.

Artificial Photosynthesis over Metal Halide Perovskites: Achievements, Challenges, and Prospects

Over the last 5 years, metal halide perovskites (MHPs) have emerged as promising photocatalysts for CO₂ reduction because of their extraodinary visible-light-harvesting capabilities and appropriate band structure. However, the CO₂ photoreduction activity of pristine MHPs is still unsatisfactory because of the phase instability, serious radiative recombination, and insufficient surface-active sites. This Perspective summarizes the strategies employed in recent studies for enhancing the photocatalytic CO₂ reduction performance of MHPs from the standpoint of structure engineering, which includes composition/dimension regulation, surface modification, and heterostructure construction. The relationship between the structure (composition, dimension, and shape) and photocatalytic performance is established, which is instructive for exploiting highly efficient perovskite-based photocatalysts in artificial photosynthesis applications. Further, some important challenges and future prospects of MHPs in this field are proposed and discussed.

Synthesis and CO2 photoreduction of two 3d–4f heterometal–organic frameworks

Two 3d–4f heterometal–organic frameworks with similar structures were synthesized by a steam-assisted conversion method and exhibited high activity and selectivity for the photoreduction of CO2.

Photocorrosion at Irradiated Perovskite/Electrolyte Interfaces

Metal-halide perovskites transformed optoelectronics research and development during the past decade. They have also gained a foothold in photocatalytic and photoelectrochemical processes recently, but their sensitivity to the most commonly applied solvents and electrolytes together with their susceptibility to photocorrosion hinders such applications. Understanding the elementary steps of photocorrosion of these materials can aid the endeavor of realizing stable devices. In this Perspective, we discuss both thermodynamic and kinetic aspects of photocorrosion processes occurring at the interface of perovskite photocatalysts and photoelectrodes with different electrolytes. We show how combined in situ and operando electrochemical techniques can reveal the underlying mechanisms. Finally, we also discuss emerging strategies to mitigate photocorrosion (such as surface protection, materials and electrolyte engineering, etc.).

Incorporation of Cesium Lead Halide Perovskites into g-C3N4 for Photocatalytic CO2 Reduction

CsPbBr₃ perovskite-based composites so far have been synthesized by postdeposition of CsPbBr₃ on a parent material. However, in situ construction offers enhanced surface contact, better activity, and improved stability. Instead of applying a typical thermal condensation at highly elevated temperatures, we report for the first time CsPb(Br _x Cl_1-x )₃/graphitic-C₃N₄ (CsPbX₃/g-C₃N₄) composites synthesized by a simple and mild solvothermal route, with enhanced efficacy in visible-light-driven photocatalytic CO₂ reduction. The composite exhibited a CO production rate of 28.5 μmol g^-1 h^-1 at an optimized loading amount of g-C₃N₄. This rate is about five times those of pure g-C₃N₄ and CsPbBr₃. This work reports a new in situ approach for constructing perovskite-based heterostructure photocatalysts with enhanced light-harvesting ability and improved solar energy conversion efficiency.