A Hierarchical Z‑Scheme α‐Fe2O3/g‐C3N4 Hybrid for Enhanced Photocatalytic CO2 Reduction

The challenge in the artificial photosynthesis of fossil resources from CO₂ by utilizing solar energy is to achieve stable photocatalysts with effective CO₂ adsorption capacity and high charge‐separation efficiency. A hierarchical direct Z‐scheme system consisting of urchin‐like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO₂ to CO, yielding a CO evolution rate of 27.2 µmol g^?1 h^?1 without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g‐C₃N₄ alone (10.3 µmol g^?1 h^?1). The enhanced photocatalytic activity of the Z‐scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin‐like hematite and preferable basic sites which promotes the CO₂ adsorption, and (ii) the unique Z‐scheme feature efficiently promotes the separation of the electron–hole pairs and enhances the reducibility of electrons in the conduction band of the g‐C₃N₄. The origin of such an obvious advantage of the hierarchical Z‐scheme is not only explained based on the experimental data but also investigated by modeling CO₂ adsorption and CO adsorption on the three different atomic‐scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal‐oxide‐based Z‐scheme system for solar fuel generation.     

In Situ Irradiated X‐Ray Photoelectron Spectroscopy Investigation on a Direct Z‐Scheme TiO2/CdS Composite Film Photocatalyst

Inspired by nature, artificial photosynthesis through the construction of direct Z‐scheme photocatalysts is extensively studied for sustainable solar fuel production due to the effectiveness in enhancing photoconversion efficiency. However, there is still a lack of thorough understanding and direct evidence for the direct Z‐scheme charge transfer in these photocatalysts. Herein, a recyclable direct Z‐scheme composite film composed of titanium dioxide and cadmium sulfide (TiO₂/CdS) is prepared for high‐efficiency photocatalytic carbon dioxide (CO₂) reduction. In situ irradiated X‐ray photoelectron spectroscopy (ISI‐XPS) confirms the direct Z‐scheme charge‐carrier migration pathway in the photocatalytic system. Furthermore, density functional theory simulation identifies the intrinsic cause for the formation of the direct Z‐scheme heterojunction between the TiO₂ and the CdS. Thanks to the significantly enhanced redox abilities of the charge carriers in the direct Z‐scheme system, the photocatalytic CO₂ reduction performance of the optimized TiO₂/CdS is 3.5, 5.4, and 6.3 times higher than that of CdS, TiO₂, and commercial TiO₂ (P25), respectively, in terms of methane production. This work is a valuable guideline in preparation of highly efficient recyclable nanocomposite for photoconversion applications.     

Interrogation of a PS1‐Based Photocathode by Means of Scanning Photoelectrochemical Microscopy

In the development of photosystem‐based energy conversion devices, the in‐depth understanding of electron transfer processes involved in photocurrent generation and possible charge recombination is essential as a basis for the development of photo‐bioelectrochemical architectures with increased efficiency. The evaluation of a bio‐photocathode based on photosystem 1 (PS1) integrated within a redox hydrogel by means of scanning photoelectrochemical microscopy (SPECM) is reported. The redox polymer acts as a conducting matrix for the transfer of electrons from the electrode surface to the photo‐oxidized P₇₀₀ centers within PS1, while methyl viologen is used as charge carrier for the collection of electrons at the reduced F_B site of PS1. The analysis of the modified surfaces by SPECM enables the evaluation of electron‐transfer processes by simultaneously monitoring photocurrent generation at the bio‐photoelectrode and the associated generation of reduced charge carriers. The possibility to visualize charge recombination processes is illustrated by using two different electrode materials, namely Au and p‐doped Si, exhibiting substantially different electron transfer kinetics for the reoxidation of the methyl viologen radical cation used as freely diffusing charge carrier. In the case of p‐doped Si, a slower recombination kinetics allows visualization of methyl viologen radical cation concentration profiles from SPECM approach curves.     

Ultrathin and Small‐Size Graphene Oxide as an Electron Mediator for Perovskite‐Based Z‐Scheme System to Significantly Enhance Photocatalytic CO2 Reduction

The judicious design of efficient electron mediators to accelerate the interfacial charge transfer in a Z‐scheme system is one of the viable strategies to improve the performance of photocatalysts for artificial photosynthesis. Herein, ultrathin and small‐size graphene oxide (USGO) nanosheets are constructed and employed as the electron mediator to elaborately exploit an efficient CsPbBr₃‐based all‐solid‐state Z‐scheme system in combination with α‐Fe₂O₃ for visible‐light‐driven CO₂ reduction with water as the electron source. CsPbBr₃ and α‐Fe₂O₃ can be closely anchored on USGO nanosheets, owing to the existence of interfacial strong chemical bonding behaviors, which can significantly accelerate the photogenerated carrier transfer between CsPbBr₃ and α‐Fe₂O₃. The resultant improved charge separation efficiency endows the Z‐scheme system exhibiting a record‐high electron consumption rate of 147.6 µmol g^?1 h^?1 for photocatalytic CO₂‐to‐CO conversion concomitant with stoichiometric O₂ from water oxidation, which is over 19 and 12 times higher than that of pristine CsPbBr₃ nanocrystals and the mixture of CsPbBr₃ and α‐Fe₂O₃, respectively. This work provides a novel and effective strategy for improving the catalytic activity of halide‐perovskite‐based photocatalysts, promoting their practical applications in the field of artificial photosynthesis.     

A Hierarchical Z‐Scheme CdS–WO3 Photocatalyst with Enhanced CO2 Reduction Activity

The development of an artificial photosynthetic system is a promising strategy to convert solar energy into chemical fuels. Here, a direct Z‐scheme CdS–WO₃ photocatalyst without an electron mediator is fabricated by imitating natural photosynthesis of green plants. Photocatalytic activities of as‐prepared samples are evaluated on the basis of photocatalytic CO₂ reduction to form CH₄ under visible light irradiation. These Z‐scheme‐heterostructured samples show a higher photocatalytic CO₂ reduction than single‐phase photocatalysts. An optimized CdS–WO₃ heterostructure sample exhibits the highest CH₄ production rate of 1.02 μmol h^?1 g^?1 with 5 mol% CdS content, which exceeds the rates observed in single‐phase WO₃ and CdS samples for approximately 100 and ten times under the same reaction condition, respectively. The enhanced photocatalytic activity could be attributed to the formation of a hierarchical direct Z‐scheme CdS–WO₃ photocatalyst, resulting in an efficient spatial separation of photo‐induced electron–hole pairs. Reduction and oxidation catalytic centers are maintained in two different regions to minimize undesirable back reactions of the photocatalytic products. The introduction of CdS can enhance CO₂ molecule adsorption, thereby accelerating photocatalytic CO₂ reduction to CH₄. This study provides novel insights into the design and fabrication of high‐performance artificial Z‐scheme photocatalysts to perform photocatalytic CO₂ reduction.     

Multichannel Charge Transfer and Mechanistic Insight in Metal Decorated 2D–2D Bi2WO6–TiO2 Cascade with Enhanced Photocatalytic Performance

Promising semiconductor‐based photocatalysis toward achieving efficient solar‐to‐chemical energy conversion is an ideal strategy in response to the growing worldwide energy crisis, which however is often practically limited by the insufficient photoinduced charge‐carrier separation. Here, a rational cascade engineering of Au nanoparticles (NPs) decorated 2D/2D Bi₂WO₆–TiO₂ (B–T) binanosheets to foster the photocatalytic efficiency through the manipulated flow of multichannel‐enhanced charge‐carrier separation and transfer is reported. Mechanistic characterizations and control experiments, in combination with comparative studies over plasmonic Au/Ag NPs and nonplasmonic Pt NPs decorated 2D/2D B–T composites, together demonstrate the cooperative synergy effect of multiple charge‐carrier transfer channels in such binanosheets‐based ternary composites, including Z‐scheme charge transfer, “electron sink,” and surface plasmon resonance effect, which integratively leads to the boosted photocatalytic performance.     

All‐Solid‐State Z‐Scheme Photocatalytic Systems

The current rapid industrial development causes the serious energy and environmental crises. Photocatalyts provide a potential strategy to solve these problems because these materials not only can directly convert solar energy into usable or storable energy resources but also can decompose organic pollutants under solar‐light irradiation. However, the aforementioned applications require photocatalysts with a wide absorption range, long‐term stability, high charge‐separation efficiency and strong redox ability. Unfortunately, it is often difficult for a single‐component photocatalyst to simultaneously fulfill all these requirements. The artificial heterogeneous Z‐scheme photocatalytic systems, mimicking the natural photosynthesis process, overcome the drawbacks of single‐component photocatalysts and satisfy those aforementioned requirements. Such multi‐task systems have been extensively investigated in the past decade. Especially, the all‐solid‐state Z‐scheme photocatalytic systems without redox pair have been widely used in the water splitting, solar cells, degradation of pollutants and CO₂ conversion, which have a huge potential to solve the current energy and environmental crises facing the modern industrial development. Thus, this review gives a concise overview of the all‐solid‐state Z‐scheme photocatalytic systems, including their composition, construction, optimization and applications.     

Ultrathin Visible‐Light‐Driven Mo Incorporating In2O3–ZnIn2Se4 Z‐Scheme Nanosheet Photocatalysts

Inspired by natural photosynthesis, the design of new Z‐scheme photocatalytic systems is very promising for boosting the photocatalytic performance of H₂ production and CO₂ reduction; however, until now, the direct synthesis of efficient Z‐scheme photocatalysts remains a grand challenge. Herein, it is demonstrated that an interesting Z‐scheme photocatalyst can be constructed by coupling In₂O₃ and ZnIn₂Se₄ semiconductors based on theoretical calculations. Experimentally, a class of ultrathin In₂O₃–ZnIn₂Se₄ (denoted as In₂O₃–ZISe) spontaneous Z‐scheme nanosheet photocatalysts for greatly enhancing photocatalytic H₂ production is made. Furthermore, Mo atoms are incorporated in the Z‐scheme In₂O₃–ZISe nanosheet photocatalyst by forming the Mo? Se bond, confirmed by X‐ray photoelectron spectroscopy, in which the formed MoSe₂ works as cocatalyst of the Z‐scheme photocatalyst. As a consequence, such a unique structure of In₂O₃–ZISe–Mo makes it exhibit 21.7 and 232.6 times higher photocatalytic H₂ evolution activity than those of In₂O₃–ZnIn₂Se₄ and In₂O₃ nanosheets, respectively. Moreover, In₂O₃–ZISe–Mo is also very stable for photocatalytic H₂ production by showing almost no activity decay for 16 h test. Ultraviolet–visible diffuse reflectance spectra, photoluminescence spectroscopy, transient photocurrent spectra, and electrochemical impedance spectroscopy reveal that the enhanced photocatalytic performance of In₂O₃–ZISe–Mo is mainly attributed to its widened photoresponse range and effective carrier separation because of its special structure.     

Efficient Photocatalytic Hydrogen Evolution via Band Alignment Tailoring: Controllable Transition from Type‐I to Type‐II

Considering the sizable band gap and wide spectrum response of tin disulfide (SnS₂), ultrathin SnS₂ nanosheets are utilized as solar‐driven photocatalyst for water splitting. Designing a heterostructure based on SnS₂ is believed to boost their catalytic performance. Unfortunately, it has been quite challenging to explore a material with suitable band alignment using SnS₂ nanomaterials for photocatalytic hydrogen generation. Herein, a new strategy is used to systematically tailor the band alignment in SnS₂ based heterostructure to realize efficient H₂ production under sunlight. A Type‐I to Type‐II band alignment transition is demonstrated via introducing an interlayer of Ce₂S₃, a potential photocatalyst for H₂ evolution, between SnS₂ and CeO₂. Subsequently, this heterostructure demonstrates tunability in light absorption, charge transfer kinetics, and material stability. The optimized heterostructure (SnS₂–Ce₂S₃–CeO₂) exhibits an incredibly strong light absorption ranging from deep UV to infrared light. Significantly, it also shows superior hydrogen generation with the rate of 240 µmol g⁻¹ h⁻¹ under the illumination of simulated sunlight with a very good stability.     

A Self‐Assembled Hetero‐Structured Inverse‐Spinel and Anti‐Perovskite Nanocomposite for Ultrafast Water Oxidation

Spinel and perovskite with distinctive crystal structures are two of the most popular material families in electrocatalysis, which, however, usually show poor conductivity, causing a negative effect on the charge transfer process during electrochemical reactions. Herein, a highly conductive inverse spinel (Fe₃O₄) and anti‐perovskite (Ni₃FeN) hetero‐structured nanocomposite is reported as a superior oxygen evolution electrocatalyst, which can be facilely prepared based on a one‐pot synthesis strategy. Thanks to the strong hybridization between Ni/Fe 3d and N 2p orbitals, the Ni₃FeN is easily transformed into NiFe (oxy)hydroxide as the real active species during the oxygen evolution reaction (OER) process, while the Fe₃O₄ component with low O‐p band center relative to Fermi level is structurally stable. As a result, both high surface reactivity and bulk electronic transport ability are reached. By directly growing Fe₃O₄/Ni₃FeN heterostructure on freestanding carbon fiber paper and testing based on the three‐electrode configuration, it requires only 160 mV overpotential to deliver a current density of 30 mA cm^?2 for OER. Also, negligible performance decay is observed within a prolonged test period of 100 h. This work sheds light on the rational design of novel heterostructure materials for electrocatalysis.     

Ultrahigh‐Sensitive Broadband Photodetectors Based on Dielectric Shielded MoTe2/Graphene/SnS2 p–g–n Junctions

2D atomic sheets of transition metal dichalcogenides (TMDs) have a tremendous potential for next‐generation optoelectronics since they can be stacked layer‐by‐layer to form van der Waals (vdW) heterostructures. This allows not only bypassing difficulties in heteroepitaxy of lattice‐mismatched semiconductors of desired functionalities but also providing a scheme to design new optoelectronics that can surpass the fundamental limitations on their conventional semiconductor counterparts. Herein, a novel 2D h‐BN/p‐MoTe₂/graphene/n‐SnS₂/h‐BN p–g–n junction, fabricated by a layer‐by‐layer dry transfer, demonstrates high‐sensitivity, broadband photodetection at room temperature. The combination of the MoTe₂ and SnS₂ of complementary bandgaps, and the graphene interlayer provides a unique vdW heterostructure with a vertical built‐in electric field for high‐efficiency broadband light absorption, exciton dissociation, and carrier transfer. The graphene interlayer plays a critical role in enhancing sensitivity and broadening the spectral range. An optimized device containing 5?7‐layer graphene has been achieved and shows an extraordinary responsivity exceeding 2600 A W^?1 with fast photoresponse and specific detectivity up to ≈10¹³ Jones in the ultraviolet–visible–near‐infrared spectrum. This result suggests that the vdW p–g–n junctions containing multiple photoactive TMDs can provide a viable approach toward future ultrahigh‐sensitivity and broadband photonic detectors.     

Tubular g‐C3N4 Isotype Heterojunction: Enhanced Visible‐Light Photocatalytic Activity through Cooperative Manipulation of Oriented Electron and Hole Transfer

A tubular g‐C₃N₄ isotype heterojunction (TCNH) photocatalyst was designed for cooperative manipulation of the oriented transfer of photogenerated electrons and holes to pursue high catalytic performance. The adduct of cyanuric acid and melamine (CA·M) is first hydrothermally treated to assemble into hexagonal prism crystals; then the hybrid precursors of urea and CA·M crystals are calcined to form tubular g‐C₃N₄ isotype heterojunctions. Upon visible‐light irradiation, the photogenerated electrons transfer from g‐C₃N₄ (CA·M) to g‐C₃N₄ (urea) driven by the conduction band offset of 0.05 eV, while the photogenerated holes transfer from g‐C₃N₄ (urea) to g‐C₃N₄ (CA·M) driven by the valence band offset of 0.18 eV, which renders oriented transfer of the charge carriers across the heterojunction interface. Meanwhile, the tubular structure of TCNH is favorable for oriented electron transfer along the longitudinal dimension, which greatly decreases the chance of charge carrier recombination. Consequently, TCNH exhibits a high hydrogen evolution rate of 63 μmol h^?1 (0.04 g, λ > 420 nm), which is nearly five times of the pristine g‐C₃N₄ and higher than most of the existing g‐C₃N₄ photocatalysts. This study demonstrates that isotype heterojunction structure and tubular structure can jointly manipulate the oriented transfer of electrons and holes, thus facilitating the visible‐light photocatalysis.     

Mesoporous Hollow Sb/ZnS@C Core–Shell Heterostructures as Anodes for High‐Performance Sodium‐Ion Batteries

Combining the advantage of metal, metal sulfide, and carbon, mesoporous hollow core–shell Sb/ZnS@C hybrid heterostructures composed of Sb/ZnS inner core and carbon outer shell are rationally designed based on a robust template of ZnS nanosphere, as anodes for high‐performance sodium‐ion batteries (SIBs). A partial cation exchange reaction based on the solubility difference between Sb₂S₃ and ZnS can transform mesoporous ZnS to Sb₂S₃/ZnS heterostructure. To get a stable structure, a thin contiguous resorcinol‐formaldehyde (RF) layer is introduced on the surface of Sb₂S₃/ZnS heterostructure. The effectively protective carbon layer from RF can be designed as the reducing agent to convert Sb₂S₃ to metallic Sb to obtain core–shell Sb/ZnS@C hybrid heterostructures. Simultaneously, the carbon outer shell is beneficial to the charge transfer kinetics, and can maintain the structure stability during the repeated sodiation/desodiation process. Owing to its unique stable architecture and synergistic effects between the components, the core–shell porous Sb/ZnS@C hybrid heterostructure SIB anode shows a high reversible capacity, good rate capability, and excellent cycling stability by turning the optimized voltage range. This novel strategy to prepare carbon‐layer‐protected metal/metal sulfide core–shell heterostructure can be further extended to design other novel nanostructured systems for high‐performance energy storage devices.     

Fast and Highly Sensitive Ionic‐Polymer‐Gated WS2–Graphene Photodetectors

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer‐scale electronic devices. Presently, long‐lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate‐voltage pulses, have been employed to achieve bandwidths suitable for applications such as video‐frame‐rate imaging. Here, atomically thin graphene–WS₂ heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10⁶. Highly mobile ions and the nanometer‐scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS₂. Responsivity R = 10⁶ A W^?1 and detectivity D* = 3.8 × 10¹¹ Jones are observed, approaching that of single‐photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video‐frame‐rate imaging applications.     

All‐Solution‐Processed Pure Formamidinium‐Based Perovskite Light‐Emitting Diodes

All‐solution‐processed pure formamidinium‐based perovskite light‐emitting diodes (PeLEDs) with record performance are successfully realized. It is found that the FAPbBr₃ device is hole dominant. To achieve charge carrier balance, on the anode side, PEDOT:PSS 8000 is employed as the hole injection layer, replacing PEDOT:PSS 4083 to suppress the hole current. On the cathode side, the solution‐processed ZnO nanoparticle (NP) is used as the electron injection layer in regular PeLEDs to improve the electron current. With the smallest ZnO NPs (2.9 nm) as electron injection layer (EIL), the solution‐processed PeLED exhibits a highest forward viewing power efficiency of 22.3 lm W^?1, a peak current efficiency of 21.3 cd A^?1, and an external quantum efficiency of 4.66%. The maximum brightness reaches a record 1.09 × 10⁵ cd m^?2. A record lifetime T₅₀ of 436 s is achieved at the initial brightness of 10 000 cd m^?2. Not only do PEDOT:PSS 8000 HIL and ZnO NPs EIL modulate the injected charge carriers to reach charge balance, but also they prevent the exciton quenching at the interface between the charge injection layer and the light emission layer. The subbandgap turn‐on voltage is attributed to Auger‐assisted energy up‐conversion process.     

High‐Efficiency All‐Small‐Molecule Organic Solar Cells Based on an Organic Molecule Donor with Alkylsilyl‐Thienyl Conjugated Side Chains

Two medium‐bandgap p‐type organic small molecules H21 and H22 with an alkylsily‐thienyl conjugated side chain on benzo[1,2‐b:4,5‐b′]dithiophene central units are synthesized and used as donors in all‐small‐molecule organic solar cells (SM‐OSCs) with a narrow‐bandgap n‐type small molecule 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC) as the acceptor. In comparison to H21 with 3‐ethyl rhodanine as the terminal group, H22 with cyanoacetic acid esters as the terminal group shows blueshifted absorption, higher charge‐carrier mobility and better 3D charge pathway in blend films. The power conversion efficiency (PCE) of the SM‐OSCs based on H22:IDIC reaches 10.29% with a higher open‐circuit voltage of 0.942 V and a higher fill factor of 71.15%. The PCE of 10.29% is among the top efficiencies of nonfullerene SM‐OSCs reported in the literature to date.     

Point‐Defect‐Passivated MoS2 Nanosheet‐Based High Performance Piezoelectric Nanogenerator

In this work, a sulfur (S) vacancy passivated monolayer MoS₂ piezoelectric nanogenerator (PNG) is demonstrated, and its properties before and after S treatment are compared to investigate the effect of passivating S vacancy. The S vacancies are effectively passivated by using the S treatment process on the pristine MoS₂ surface. The S vacancy site has a tendency to covalently bond with S functional groups; therefore, by capturing free electrons, a S atom will form a chemisorbed bond with the S vacancy site of MoS₂. S treatment reduces the charge‐carrier density of the monolayer MoS₂ surface, thus the screening effect of piezoelectric polarization charges by free carrier is significantly prevented. As a result, the output peak current and voltage of the S‐treated monolayer MoS₂ nanosheet PNG are increased by more than 3 times (100 pA) and 2 times (22 mV), respectively. Further, the S treatment increases the maximum power by almost 10 times. The results suggest that S treatment can reduce free‐charge carrier by sulfur S passivation and efficiently prevent the screening effect. Thus, the piezoelectric output peaks of current, voltage, and maximum power are dramatically increased, as compared with the pristine MoS₂.     

A Quasi‐Solid‐State Flexible Fiber‐Shaped Li–CO2 Battery with Low Overpotential and High Energy Efficiency

The rapid development of wearable electronics requires a revolution of power accessories regarding flexibility and energy density. The Li–CO₂ battery was recently proposed as a novel and promising candidate for next‐generation energy‐storage systems. However, the current Li–CO₂ batteries usually suffer from the difficulties of poor stability, low energy efficiency, and leakage of liquid electrolyte, and few flexible Li–CO₂ batteries for wearable electronics have been reported so far. Herein, a quasi‐solid‐state flexible fiber‐shaped Li–CO₂ battery with low overpotential and high energy efficiency, by employing ultrafine Mo₂C nanoparticles anchored on a carbon nanotube (CNT) cloth freestanding hybrid film as the cathode, is demonstrated. Due to the synergistic effects of the CNT substrate and Mo₂C catalyst, it achieves a low charge potential below 3.4 V, a high energy efficiency of ≈80%, and can be reversibly discharged and charged for 40 cycles. Experimental results and theoretical simulation show that the intermediate discharge product Li₂C₂O₄ stabilized by Mo₂C via coordinative electrons transfer should be responsible for the reduction of overpotential. The as‐fabricated quasi‐solid‐state flexible fiber‐shaped Li–CO₂ battery can also keep working normally even under various deformation conditions, giving it great potential of becoming an advanced energy accessory for wearable electronics.     

Quantifying Polaron Formation and Charge Carrier Cooling in Lead‐Iodide Perovskites

Notwithstanding the success of lead‐halide perovskites in emerging solar energy conversion technologies, many of the fundamental photophysical phenomena in this material remain debated. Here, the initial steps following photogeneration of free charge carriers in lead‐iodide perovskites are studied, and timescales of charge carrier cooling and polaron formation, as a function of temperature and charge carrier excess energy, are quantified. It is found, using terahertz time‐domain spectroscopy (THz‐TDS), that the observed femtosecond rise in the photoconductivity can be described very well using a simple model of sequential charge carrier cooling and polaron formation. For excitation above the bandgap, the carrier cooling time depends on the charge carrier excess energy and lattice temperature, with cooling rates varying between 1 and 6 meV fs^?1, depending on the cation. While carrier cooling depends on the cation, polaron formation occurs within ≈400 fs in CH₃NH₃PbI₃ (MAPbI₃), CH(NH₂)₂PbI₃ (FAPbI₃), and CsPbI₃. Its formation time is independent of temperature between 160 and 295 K. The very similar polaron formation dynamics observed for the three perovskites points to the critical role of the inorganic lattice, rather than the cations, for polaron formation.     

Photocatalytic Conversion of CO2 into Renewable Hydrocarbon Fuels: State‐of‐the‐Art Accomplishment,Challenges, and Prospects

Photocatalytic reduction of CO₂ into hydrocarbon fuels, an artificial photosynthesis, is based on the simulation of natural photosynthesis in green plants, whereby O₂ and carbohydrates are produced from H₂O and CO₂ using sunlight as an energy source. It couples the reductive half‐reaction of CO₂ fixation with a matched oxidative half‐reaction such as water oxidation, to achieve a carbon neutral cycle, which is like killing two birds with one stone in terms of saving the environment and supplying future energy. The present review provides an overview and highlights recent state‐of‐the‐art accomplishments of overcoming the drawback of low photoconversion efficiency and selectivity through the design of highly active photocatalysts from the point of adsorption of reactants, charge separation and transport, light harvesting, and CO₂ activation. It specifically includes: i) band‐structure engineering, ii) nanostructuralization, iii) surface oxygen vacancy engineering, iv) macro‐/meso‐/microporous structuralization, v) exposed facet engineering, vi) co‐catalysts, vii) the development of a Z‐scheme system. The challenges and prospects for future development of this field are also present.