Chemical Pressure-Driven Band Convergence and Discordant Atoms Intensify Phonon Scattering Leading to High Thermoelectric Performance in SnTe.

SnTe is an intriguing alternative to PbTe for midtemperature thermoelectric applications. Despite steady progress, its performance is lagging, in part because of the large energy difference(ΔEL-Σ) between the light (L-band) and heavy (Σ-band) valence bands and higher lattice thermal conductivity (κL). Previous studies have shown that applying pressure can enhance the Seebeck coefficient (S) and power factor (PF) of SnTe. Inspired by this study, we showcase how the high-pressure effect can be emulated under ambient pressure by substituting Sn with atoms possessing smaller atomic radii. Specifically, Sb- and Ge-doping combined with CdTe- or CdS-alloying induce lattice shrinkage, also referred to as "chemical pressure", raising the energy of the Σ-band. Additionally, these substituted atoms lower the contribution of Sn 5s-Te 5p antibonding states to the L-band, thereby reducing its energy and dispersion. These combined effects decrease ΔEL-Σ from 0.36 to 0.09 eV, leading to the enhanced S and average PFavg. Notably, the PFavg, ranging from 323 to 873 K, increases from 8.1 µW cm-1 K-2 for pristine SnTe to 21.6 µW cm-1 K-2 for Sn0.79Ge0.15Sb0.06Te-5% CdTe. Furthermore, the intensified phonon scattering resulting from discordant nature of Ge and Cd atoms, creating point defects soften phonon modes, and the presence of Ge-rich nanoprecipitates lead to a substantial 62% reduction in κL at 873 K. This strong valence band convergence and enhanced phonon scattering collectively contribute to a high peak ZT of 1.5 (873 K) and high average ZTavg = 0.81 over the temperature range of 323-873 K.

Unlocking Copper-Free Interfacial Asymmetric C-C Coupling for Ethylene Photosynthesis from CO2 and H2O.

Solar-driven carbon dioxide (CO2) reduction into C2+ products such as ethylene represents an enticing route toward achieving carbon neutrality. However, due to sluggish electron transfer and intricate C-C coupling, it remains challenging to achieve highly efficient and selective ethylene production from CO2 and H2O beyond capitalizing on Cu-based catalysts. Herein, we report a judicious design to attain asymmetric C-C coupling through interfacial defect-rendered tandem catalytic centers within a sulfur-vacancy-rich MoSx/Fe2O3 photocatalyst sheet, enabling a robust CO2 photoreduction to ethylene without the need for copper, noble metals, and sacrificial agents. Specifically, interfacial S vacancies induce adjacent under-coordinated S atoms to form Fe-S bonds as a rapid electron-transfer pathway for yielding a Z-scheme band alignment. Moreover, these S vacancies further modulate the strong coupling interaction to generate a nitrogenase-analogous Mo-Fe heteronuclear unit and induce the upward shift of the d-band center. This bioinspired interface structure effectively suppresses electrostatic repulsion between neighboring *CO and *COH intermediates via d-p hybridization, ultimately facilitating an asymmetric C-C coupling to achieve a remarkable solar-to-chemical efficiency of 0.565% with a superior selectivity of 84.9% for ethylene production. Further strengthened by MoSx/WO3, our design unveils a promising platform for optimizing interfacial electron transfer and offers a new option for C2+ synthesis from CO2 and H2O using copper-free and noble metal-free catalysts.

Melting and Rapid Solidification of Lunar Regolith Particles Returned by Chang'E-5 Mission.

Melting and solidification of lunar regolith are pivotal for comprehending the evolutionary dynamics of lunar volcanism, geology, and impact history. Additionally, insights gained from these processes can contribute to the advancement of in situ resource utilization technologies, for instance additive manufacturing and resource extraction systems. Herein, we conduct the direct observation of the melting and rapid solidification of lunar particles returned by the Chang'E 5 mission. The melting temperature and melting sequence were obtained. Bubble generation, growth, and release were clearly observed, with a maximum bubble diameter of 5 µm, which is supposed to be according to the release of volatiles that embedded in the particles. During the solidification process, evident crystallization occurred with incremental crystal growth rate approximately of 27 nm/s. Scanning electron microscopy and energy-dispersive x-ray spectroscopy results verified that the Fe-rich mineral crystalizes first. These results would improve the understanding of the evolution of lunar volcanism, geology, and impact history.

Massive water production from lunar ilmenite through reaction with endogenous hydrogen.

Finding water resources is a crucial objective of lunar missions. However, both hydroxyl (OH) and natural water (H2O) have been reported to be scarce on the Moon. We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith (LR), specifically through the reaction FeO/Fe2O3 + H → Fe + H2O. This process is demonstrated using LR samples brought back by the Chang'E-5 mission. FeO and Fe2O3 are lunar minerals containing Fe oxides. Hydrogen (H) retained in lunar minerals from the solar wind can be used to produce water. The results of this study reveal that 51-76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K. This amount is ∼10,000 times the naturally occurring OH and H2O on the Moon. Among the five primary minerals in LR returned by the Chang'E-5 mission, FeTiO3 ilmenite contains the highest amount of H, owing to its unique lattice structure with sub-nanometer tunnels. For the first time, in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles. Electron irradiation promotes the endogenous redox reaction, which is helpful for understanding the distribution of OH on the Moon. Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon, which is helpful for establishing a scientific research station on the Moon.

Defect Engineering of Ultrasmall TiO2 Nanoparticles Enables Highly Efficient Photocatalysts for Solar H2 Production from Woody Biomass.

The conversion of woody biomass to H2 through photocatalysis provides a sustainable strategy to generate renewable hydrogen fuel but was limited by the slow decomposition rate of woody biomass. Here, we fabricate ultrasmall TiO2 nanoparticles with tunable concentration of oxygen vacancy defects (VO-TiO2) as highly efficient photocatalysts for photocatalytic conversion of woody biomass to H2. Owing to the positive role of oxygen vacancy in reducing energy barrier for the generation of •OH which was the critical species to oxidize woody biomass, the obtained VO-TiO2 achieves rapid photocatalytic conversion of α-cellulose and poplar wood chip to H2 in the presence of Pt nanoclusters as the cocatalyst. As expected, the highest H2 generation rate in α-cellulose and poplar wood chip system respectively achieve 1146 and 59 µmol h-1 g-1, and an apparent quantum yield of 4.89% at 380 nm was obtained in α-cellulose aqueous solution.

Multi-Modal Sensing Ionogels with Tunable Mechanical Properties and Environmental Stability for Aquatic and Atmospheric Environments.

Ionogels have garnered significant interest due to their great potential in flexible iontronic devices. However, their limited mechanical tunability and environmental intolerance have posed significant challenges for their integration into next-generation flexible electronics in different scenarios. Herein, the synergistic effect of cation-oxygen coordination interaction and hydrogen bonding is leveraged to construct a 3D supramolecular network, resulting in ionogels with tunable modulus, stretchability, and strength, achieving an unprecedented elongation at break of 10 800%. Moreover, the supramolecular network endows the ionogels with extremely high fracture energy, crack insensitivity, and high elasticity. Meanwhile, the high environmental stability and hydrophobic network of the ionogels further shield them from the unfavorable effects of temperature variations and water molecules, enabling them to operate within a broad temperature range and exhibit robust underwater adhesion. Then, the ionogel is assembled into a wearable sensor, demonstrating its great potential in flexible sensing (temperature, pressure, and strain) and underwater signal transmission. This work can inspire the applications of ionogels in multifunctional sensing and wearable fields.

Rationally designed hierarchical hollow CuS/CdIn2S4 heterostructure nanoboxes for boosted photoreduction of CO2.

A novel double-shelled CuS/CdIn2S4 photocatalyst was rationally designed using CdIn2S4 sheets in situ grown upon the exterior of hollow CuS nanocubes. The unique hierarchical hollow structure of CuS/CdIn2S4 provides numerous active sites and reduces carrier diffusion length. Surface sulfur vacancies mitigate the detachment of the intermediate, which is favorable for a multi-electron reaction path such as that in the production of CH4. Meanwhile, a suitable band-structure alignment between p-type CuS and n-type CdIn2S4 leads to the formation of a type-II heterostructure, thus resulting in effective light-harvesting and spatial separation of electron-hole pairs for CO2 photoreduction. The CuS/CdIn2S4 heterostructure exhibits significantly enhanced performance with a boosted CO yield of 40.73 µmol g-1 h-1 as well as a noticeably improved CH4 selectivity (36.5%, 23.41 µmol g-1 h-1). This work introduces innovative concepts in designing photocatalytic systems with unique morphologies and rational band structures, promising advancements in CO2 photoreduction at reduced costs.

Outstanding CO2 Photoreduction in Single-Atom Thulium Modified Carbon Nitride.

CO2 reduction photocatalysts are favorable for obtaining renewable energy. Enriched active sites and effective photogenerated-carriers separation are keys for improving CO2 photo-reduction. A thulium (Tm) single atom tailoring strategy introducing carbon vacancies in porous tubular graphitic carbon nitride (g-C3N4) surpassing the ever-reported g-C3N4 based photocatalysts, with 199.47 µmol g-1 h-1 CO yield, 96.8% CO selectivity, 0.84% apparent quantum efficiency and excellent photocatalytic stability, is implemented in this work. Results revealed that in-plane Tm sites and interlayer-bridged Tm-N charge transfer channels significantly enhanced the aggregation/transfer of photogenerated electrons thus promoting CO2 adsorption/activation and contributing to *COOH intermediates formation. Meanwhile, Tm atoms and carbon vacancies both benefit for rich active sites and enhanced photogenerated-charge separation, thus optimizing reaction pathway and leading to excellent CO2 photo-reduction. This work not only provides guidelines for CO2 photo-reduction catalysts design but also offers mechanistic insights into single-atom based photocatalysts for solar fuel production.

Thermal Migration to Recover Spent Pt/C Catalyst.

Recovery of spent Pt/C catalyst is a sustainable low-cost route to promote large-scale application of hydrogen fuel cells. Here, we report a thermal migration strategy to recover the spent Pt/C. In this route, the ZIF-8 is used to produce nitrogen doped porous carbon (NC) with abundant pyrimidine nitrogen sites as the new support. Subsequently, the spent Pt/C, NC, and NH4Cl etching reagent are mixed and heated at 900 oC to thermally migrate Pt from Pt/C onto NC with the help of NH4Cl etching reagent. The thermal-volatilized Pt tends to be captured by the pyrimidine nitrogen sites of NC support, thus producing the Pt clusters or 4 - 5 nm Pt particles. The recovered Pt/NC catalyst exhibits the highly stable oxygen reduction activities with a mass activity of 0.6 A mgPt-1 after 30000-cycle accelerated durability test.

Recent advances of metal active sites in photocatalytic CO2 reduction.

Photocatalytic CO2 reduction captures solar energy to convert CO2 into hydrocarbon fuels, thus shifting the dependence on rapidly depleting fossil fuels. Among the various proposed photocatalysts, systems containing metal active sites (MASs) possess obvious advantages, such as effective photogenerated carrier separation, suitable adsorption and activation of intermediates, and achievable C-C coupling to generate multi-carbon (C2+) products. The present review aims to summarize the typical photocatalytic materials with MAS, highlighting the critical role of different formulations of MAS in CO2 photoreduction, especially for C2+ product generation. State-of-the-art progress in the characterization and theoretical calculations for MAS-containing photocatalysts is also emphasized. Finally, the challenges and prospects of catalytic systems involving MAS for solar-driven CO2 conversion are outlined, providing inspiration for the future design of materials for efficient photocatalytic energy conversion.

Dopamine-Carbonized Coating PtCo Catalyst with Enhanced Durability toward the Oxygen Reduction Reaction.

Stability is the main challenge for the application of PtCo catalysts because Co tends to leach during the electrochemical reaction. Herein, we immerse and adsorb dopamine to densely coat Pt0.8Co0.2 particles and subsequently thermally carbonize the coating into few-layer nitrogen-doped graphene to produce Pt0.8Co0.2@NC. This coating effectively hinders direct contact between Pt0.8Co0.2 particles and the electrolyte, thereby enhancing the stability of the catalyst by preventing Ostwald ripening and suppressing competitive adsorption of toxic species, while also bolstering its antipoisoning ability. Experimental results indicate that the thin coating does not compromise the oxygen reduction reaction activity of the catalyst, showcasing a half-wave potential of 0.81 V in alkaline electrolytes. Spectroscopic results suggest that a strong bonding interaction between Pt and the pyridinic N of N-doped graphene contributes to the generation of a dense coating. The coating layer does not affect the four-electron reaction mechanism of the Pt0.8Co0.2 alloy, and the coordinatively unsaturated carbon atoms on Pt0.8Co0.2@NC serve as active oxygen reduction reaction centers.

Synthesis of Sulfur Vacancy-Bearing In2S3/CuInS2 Microflower Heterojunctions via a Template-Assisted Strategy and Cation-Exchange Reaction for Photocatalytic CO2 Reduction.

The synthesis of the accurate composition and morphological/structural design of multielement semiconductor materials is considered an effective strategy for obtaining high-performance hybrid photocatalysts. Herein, sulfur vacancy (Vs)-bearing In2S3/CuInS2 microflower heterojunctions (denoted Vs-In2S3/CuInS2) were formed in situ using In2S3 microsphere template-directed synthesis and a metal ion exchange-mediated growth strategy. Photocatalysts with flower-like microspheres can be obtained using hydrothermally synthesized In2S3 microspheres as a template, followed by Ostwald ripening growth during the metal cation exchange of Cu+ and In3+. The optimal heterostructured Vs-In2S3/CuInS2 microflowers exhibited CO and CH4 evolution rates of 80.3 and 11.8 µmol g-1 h-1, respectively, under visible-light irradiation; these values are approximately 4 and 6.8 times higher than those reported for pristine In2S3, respectively. The enhanced photocatalytic performance of the Vs-In2S3/CuInS2 catalysts could be attributed to the synergistic effects of the following factors: (i) the constructed heterojunctions accelerate charge-carrier separation; (ii) the flower-like microspheres exhibit highly uniform morphologies and compositions, which enhance electron transport and light harvesting; and (iii) the vs. may trap excited electrons and, thus, inhibit charge-carrier recombination. This study not only confirms the feasibility of the design of heterostructures on demand, but also presents a simple and efficient strategy to engineer metal sulfide photocatalysts with enhanced photocatalytic performance.

Strong Electronic Interaction Enables Enhanced Solar-Driven CO2 Reduction into Selective CH4 on SrTiO3 with Photodeposited Pt2+ Sites.

Targeting selective CO2 photoreduction into CH4 remains a challenge due to the sluggish reaction kinetics and poor hydrogenation ability of the unstable intermediate. Here, the active Pt2+ sites were photodeposited on the SrTiO3 photocatalyst, which was well demonstrated to manipulate the CH4 product selectivity. The results showed that SrTiO3 mainly yielded the CO (6.98 µmol g-1) product with poor CH4 (0.17 µmol g-1). With the Pt2+ modification, 100% CH4 selectivity could be obtained with an optimized yield rate of 8.07 µmol g-1. The prominent enhancement resulted from the following roles: (1) the strong electronic interaction between the Pt2+ cocatalyst and SrTiO3 could prompt efficient separation of the photoelectron-hole pairs. (2) The Pt2+ sites were active to capture and activate inert CO2 into HCO3- and CO32- species and allowed fast *COOH formation with the lowered reaction barrier. (3) Compared with SrTiO3, the formed *CO species could be captured tightly on the Pt2+ cocatalyst surface for generating the *CH2 intermediate by the following electron-proton coupling reaction, thus leading to the CH4 product with 100% selectivity.

Efficient Holes Abstraction by Precisely Decorating Ruthenium Single Atoms and RuOx Clusters on ZnIn2S4 for Photocatalytic Pure Water Splitting.

Developing efficient photocatalysts for two-electron water splitting with simultaneous H2O2 and H2 generation shows great promise for practical application. Currently, the efficiency of two-electron water splitting is still restricted by the low utilization of photogenerated charges, especially holes, of which the transfer rate is much slower than that of electrons. Herein, Ru single atoms and RuOx clusters are co-decorated on ZnIn2S4 (RuOx/Ru-ZIS) to employ as multifunctional sites for efficient photocatalytic pure water splitting. Doping of Ru single atoms in the ZIS basal plane enhances holes abstraction from bulk ZIS by regulating the electronic structure, and RuOx clusters offer a strong interfacial electric field to remarkably promote the out-of-plane migration of holes from ZIS. Moreover, Ru single atoms and RuOx clusters also serve as active sites for boosting surface water oxidation. As a result, an excellent H2 and H2O2 evolution rates of 581.9 µmol g-1 h-1 and 464.4 µmol g-1 h-1 is achieved over RuOx/Ru-ZIS under visible light irradiation, respectively, with an apparent quantum efficiency (AQE) of 4.36% at 400 nm. This work paves a new way to increase charge utilization by manipulating photocatalyst using single atom and clusters.

Evolution of Naturally Dried MXene-Based Composite Aerogels with Flash Joule Annealing for Large-Scale Production of Highly Sensitive Customized Sensors.

MXene aerogels, known for good electrical properties, offer immense potential for the development of high-sensitivity pressure sensors. However, the intrinsic challenges stemming from the poor self-assembly capability and high hydrophilicity of MXene impede the natural drying process of MXene-based hydrogels, thereby constraining their application on a large scale in sensor technology. Herein, a graphene-assisted approach aimed at modulating the hydrophobicity and enhancing framework strength of MXene through a well-designed prefreezing technique incorporating 3D spherical macroporous structures is proposed. This synergistic strategy enables the fabrication of naturally dried MXene aerogels across various size scales. Moreover, the integration of 3D spherical macroporous structures improves elasticity and electrical responsiveness of aerogels. Consequently, the aerogel sensor exhibits great performances, including high sensitivity (1250 kPa-1), low detection limit (0.4 Pa), wide frequency response range (0.1-8 Hz), and excellent stability (1000 cycles). This sensor proves adept at monitoring pressure signals ranging from lightweight paper to human motion. Additionally, the application of customized laser engraving endows aerogels with unique functionalities, such as compressibility and immunity to strain, stretchability and resistance to compression, as well as wind detection. Thus, the proposed approach holds significant promise as a scalable method for the mass production of aerogels with versatile applications.

Lattice Oxygen in Photocatalytic Gas-Solid Reactions: Participator vs. Dominator.

Lattice-oxygen activation has emerged as a popular strategy for optimizing the performance and selectivity of oxide-based thermocatalysis and electrolysis. However, the significance of lattice oxygen in oxide photocatalysts has been ignored, particularly in gas-solid reactions. Here, using methane oxidation over a Ru1@ZnO single-atom photocatalyst as the prototypical reaction and via 18O isotope labelling techniques, we found that lattice oxygen can directly participate in gas-solid reactions. Lattice oxygen played a dominant role in the photocatalytic reaction, as determined by estimating the kinetic constants in the initial stage. Furthermore, we discovered that dynamic diffusion between O2 and lattice oxygen proceeded even in the absence of targeted reactants. Finally, single-atom Ru can facilitate the activation of adsorbed O2 and the subsequent regeneration of consumed lattice oxygen, thus ensuring high catalyst activity and stability. The results provide guidance for next-generation oxide photocatalysts with improved activities and selectivities.

Thermal-Stabilized Protonated TiO2 for Heat-Accelerated Photoelectrochemical Water Splitting.

Enhancing the charge separation efficiency is a big challenge that limits the energy conversion efficiency of photoelectrochemical (PEC) water splitting. Surface states generated by protonation of TiO2 are the efficient charge separation passageways to massively accept or transfer the photogenerated electrons. However, a challenge is to avoid the deprotonation of a protonated TiO2 photoelectrode at the operation temperature. Here, we found that the terminal hydroxyl group (OHT) as surface states on the TiO2 surface generated via electrochemical protonation of TiO2 at 90 °C [90-TiO2-x-(OH)x] is thermally stable. As a result, the thermally enhanced photocurrent of the 90-TiO2-x-(OH)x electrode reached 1.05 mA cm-2 under 80 °C, and the stability was maintained up to 10 h with a slight photocurrent decrease of 3%. The thermally stable surface states as charge separation paths provide an effective method to couple the heat field with the PEC process via thermal-stimulating hopping of polarons.

Stable CO2reduction under natural air on Ni-Sn hydroxide photocatalyst with dynamic renewable oxygen vacancies.

Advanced photocatalysts are highly desired to activate the photocatalytic CO2reduction reaction (CO2RR) with low concentration. Herein, the NiSn(OH)6with rich surface lattice hydroxyls was synthesized to boost the activity directly under the natural air. Results showed that terminal Ni-OH could serve as donors to feed protons and generate oxygen vacancies (VO), thus beneficial to convert the activated CO2(HCO3-) mainly into CO (5.60µmol g-1) in the atmosphere. It was flexible and widely applicable for a stable CO2RR from high pure to air level free of additionally adding H2O reactant, and higher than the traditional gas-liquid-solid (1.58µmol g-1) and gas-solid (4.07µmol g-1) reaction system both using high pure CO2and plenty of H2O. The strong hydrophilia by the rich surface hydroxyls allowed robust H2O molecule adsorption and dissociation at VOsites to achieve the Ni-OH regeneration, leading to a stable CO yield (11.61µmol g-1) with the enriched renewable VOregardless of the poor CO2and H2O in air. This work opens up new possibilities for the practical application of natural photosynthesis.

Photothermal CO2 Catalysis toward the Synthesis of Solar Fuel: From Material and Reactor Engineering to Techno-Economic Analysis.

Carbon dioxide (CO2), a member of greenhouse gases, contributes significantly to maintaining a tolerable environment for all living species. However, with the development of modern society and the utilization of fossil fuels, the concentration of atmospheric CO2 has increased to 400 ppm, resulting in a serious greenhouse effect. Thus, converting CO2 into valuable chemicals is highly desired, especially with renewable solar energy, which shows great potential with the manner of photothermal catalysis. In this review, recent advancements in photothermal CO2 conversion are discussed, including the design of catalysts, analysis of mechanisms, engineering of reactors, and the corresponding techno-economic analysis. A guideline for future investigation and the anthropogenic carbon cycle are provided.