Latest ArticlesA series of “half-sandwich” bis(imino)pyridyl iron complexes with a substituted 8-(p-X-phenyl)naphthylamine (X = OMe, Me, CF3) was designed and synthesized by combining weak π-π interaction with steric and electronic tunings. The weak noncovalent π-π interaction as well as the steric and electronic effects of bis(imino)pyridyl iron complexes were identified by experimental analyses and calculations. The roles of weak π-π interaction, steric bulk, and electronic tuning on the ethylene polymerization performance of bis(imino)pyridyl iron catalysts were studied in detail. The combination of π-π interaction with steric and electronic tunings can access to thermally stable bis(imino)pyridyl iron at 130 ℃.
Proton exchange membrane water electrolysis (PEMWE) is a favorable technology for producing high-purity hydrogen under high current density using intermittent renewable energy. The performance of PEMWE is largely determined by the oxygen evolution reaction (OER), a sluggish four-electron reaction with a high reaction barrier. Nowadays, iridium (Ir)-based catalysts are the catalysts of choice for OER due to their excellent activity and durability in acidic solution. However, its high price and unsatisfactory electrochemical performance severely restrict the PEMWE’s practical application. In this review, we initiate by introducing the current OER reaction mechanisms, namely adsorbate evolution mechanism and lattice oxygen mechanism, with degradation mechanisms discussed. Optimized strategies in the preparation of advanced Ir-based catalysts are further introduced, with merits and potential problems also discussed. The parameters that determine the performance of PEMWE are then introduced, with unsolved issues and related outlooks summarized in the end.
Polycyclic compounds are widely found in natural products and drug molecules with important biological activities, which attracted the attention of many chemists. Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy, mild reaction conditions and simplicity of operation. Allenolates, Morita−Baylis−Hillman (MBH) alcohols and their derivatives (MBHADs), electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations, which formed many phosphonium species such as β-phosphonium enolates, β-phosphonium dienolates and vinyl phosphonium ylides as intermediates. This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations. Thus, a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates, MBH alcohols and MBHADs, electron-deficient olefins and alkynes are presented in Chapters 2–6, respectively.
Transition metal cobalt exhibits strong activation capabilities for alkanes, however, the instability of Co sites leads to sintering and coke deposition, resulting in rapid deactivation. Hierarchical zeolites, with their diverse pore structures and high surface areas, are used to effectively anchor metals and enhance coke tolerance. Herein, a post-treatment method using an alkaline solution was employed to synthesize meso-microporous zeolite supports, which were subsequently loaded with Co species for propane dehydrogenation catalyst. The results indicate that the application of NaOH, an inorganic base, produces supports with a larger mesopore volume and more abundant hydroxyl nests compared to TPAOH, an organic base. UV–vis, Raman, and XPS analyses reveal that Co in the 0.5Co/SN-1–0.05 catalyst is mainly in the form of tetrahedral Co2+, which effectively activates CH bonds. In contrast, the 0.5Co/S-1 catalyst contains mainly Co3O4 species. Co2+ supported on hierarchical zeolites shows better propane conversion (58.6%) and propylene selectivity (>96%) compared to pure silica zeolites. Coke characterization indicates that hierarchical zeolites accumulate more coke, but it is mostly in the form of easily removable disordered carbon. The mesopores in the microporous zeolite support help disperse the active Co metal and facilitate coke removal during dehydrogenation, effectively preventing deactivation from sintering and coke coverage.
Although lithium-ion batteries (LIBs) currently dominate a wide spectrum of energy storage applications, they face challenges such as fast cycle life decay and poor stability that hinder their further application. To address these limitations, element doping has emerged as a prevalent strategy to enhance the discharge capacity and extend the durability of Li-Ni-Co-Mn (LNCM) ternary compounds. This study utilized a machine learning-driven feature screening method to effectively pinpoint four key features crucially impacting the initial discharge capacity (IC) of Li-Ni-Co-Mn (LNCM) ternary cathode materials. These features were also proved highly predictive for the 50th cycle discharge capacity (EC). Additionally, the application of SHAP value analysis yielded an in-depth understanding of the interplay between these features and discharge performance. This insight offers valuable direction for future advancements in the development of LNCM cathode materials, effectively promoting this field toward greater efficiency and sustainability.
Cu-based metal-organic frameworks (MOFs) are widely employed in CO2 reduction reactions (CO2RR). Mostly, the in-situ reconstructed derivatives such as Cu or Cu oxides during CO2RR are regarded as the catalytic active center for the formation of catalytic products. However, in many cases, the pristine MOFs still exist during the catalytic process, the key role of these pristine MOFs is often ignored in revealing the catalytic mechanism. Here, we designed two Cu(imidazole) with different coordination environments, namely CuN2 and Cu2N4 for CO2RR. The structures of the two MOFs were still remained after the catalytic reaction. We discovered that the pristine MOFs served as activation catalysts for converting CO2 into CO. Sequentially, the Cu-based derivatives, in the two cases, Cu(111) converted the CO into C2+ products. The CuN2 with more exposed Cu-N centers showed a higher FECO and a higher final FEC2+ than Cu2N4. This auto-tandem catalytic mechanism was supported by electrocatalytic performance, TPD-CO, HRTEM, SAED, XPS, in-situ XANES and XES and DFT computation. The auto-tandem catalytic mechanism provides a new route to design Cu-based MOF electrocatalysts for high product selectivity in CO2RR.
Mn-based P2-type oxides are considered as promising cathodes for Na-ion batteries; however, they face significant challenges, including structural degradation when charged at high cutoff voltages and structural changes upon storing in a humid atmosphere. In response to these issues, we have designed an oxide with co-doping of Cu and Al which can balance both cost and structural stability. The redox reaction of Cu2+/3+ can provide certain charge compensation, and the introduction of Al can further suppress the Jahn-Teller effect of Mn, thereby achieving superior long-term cycling performance. The ex-situ XRD testing indicates that Cu/Al co-doping can effectively suppress the phase transition of P2-O2 at high voltage, thereby explaining the improvement in electrochemical performance. DFT calculations reveal a high chemical tolerance to moisture, with lower adsorption energy for H2O compared to pure Na0.67Cu0.25Mn0.75O2. A representative Na0.67Cu0.20Al0.05Mn0.75O2 cathode demonstrates impressive reversible capacities of 148.7 mAh/g at 0.2 C, along with a remarkable capacity retention of 79.1% (2 C, 500 cycles).
Industrial high-current-density oxygen evolution catalyst is the key to accelerating the practical application of hydrogen energy. Herein, Co9S8/CoS heterojunctions were rationally encapsulated in S, N-codoped carbon ((Co9S8/CoS)@SNC) microleaf arrays, which are rooted on S-doped carbonized wood fibers (SCWF). Benefiting from the synergistic electronic interactions on heterointerfaces and the accelerated mass transfer by array structure, the obtained self-supporting (Co9S8/CoS)@SNC/SCWF electrode exhibits superior performance toward alkaline oxygen evolution reaction (OER) with an ultra-low overpotential of 274 mV at 1000 mA/cm2, a small Tafel slope of 48.84 mV/dec, and ultralong stability up to 100 h. Theoretical calculations show that interfacing Co9S8 with CoS can upshift the d-band center of the Co atoms and strengthen the interactions with oxygen intermediates, thereby favoring OER performance. Furthermore, the (Co9S8/CoS)@SNC/SCWF electrode shows outstanding rechargeability and stable cycle life in aqueous Zn-air batteries with a peak power density of 201.3 mW/cm2, exceeding the commercial RuO2 and Pt/C hybrid catalysts. This work presents a promising strategy for the design of high-current-density OER electrocatalysts from sustainable wood fiber resources, thus promoting their practical applications in the field of electrochemical energy storage and conversion.
Carbon monoxide (CO) is a crucial gaseous signaling molecule that regulates various physiological and pathological processes, and may exert an anti-inflammatory and protective role in drug-induced liver injury (DILI). Despite this, understanding the exact relationship between CO and the occurrence and development of DILI remains challenging. Hence, there is an urgent need to develop a reliable and robust tool for the rapid visual detection and assessment of CO in this context. Herein, we presented a novel near-infrared (NIR) fluorescent nanoprobe with aggregation-induced emission (AIE) properties and excited-state intramolecular proton transfer (ESIPT) characteristics for the detection and imaging of CO both in vitro and in vivo. Simultaneously, the nanoprobe enables self-assembly form nanoaggregates in aqueous media with high biocompatible, which can sense CO in situ through the conversion of yellow-to-red fluorescence facilitated aggregation-induced dual-color fluorescence. What is more, this nanoprobe shows ratiometric respond to CO, which demonstrates excellent stability, high sensitivity (with a detection limit of 12.5 nmol/L), and superior selectivity. Crucially, this nanoprobe enables the visual detection of exogenous and endogenous CO in living cells and tissues affected by DILI, offering a user-friendly tool for real-time visualization of CO in living system. Hence, it holds great promise in advancing our understanding of CO's role.
Solid-state electrolytes (SSEs), as the core component within the next generation of key energy storage technologies - solid-state lithium batteries (SSLBs) - are significantly leading the development of future energy storage systems. Among the numerous types of SSEs, inorganic oxide garnet-structured superionic conductors Li7La3Zr2O12 (LLZO) crystallized with the cubic Ia3d space group have received considerable attention owing to their highly advantageous intrinsic properties encompassing reasonable lithium-ion conductivity, wide electrochemical voltage window, high shear modulus, and excellent chemical stability with electrodes. However, no SSEs possess all the properties necessary for SSLBs, thus both the ionic conductivity at room temperature and stability in ambient air regarding cubic garnet-based electrolytes are still subject to further improvement. Hence, this review comprehensively covers the nine key structural factors affecting the ion conductivity of garnet-based electrolytes comprising Li concentration, Li vacancy concentration, Li carrier concentration and mobility, Li occupancy at available sites, lattice constant, triangle bottleneck size, oxygen vacancy defects, and Li-O bonding interactions. Furthermore, the general illustration of structures and fundamental features being crucial to chemical stability is examined, including Li concentration, Li-site occupation behavior, and Li-O bonding interactions. Insights into the composition-structure-property relations among cubic garnet-based oxide ionic conductors from the perspective of their crystal structures, revealing the potential compatibility conflicts between ionic transportation and chemical stability resulting from Li-O bonding interactions. We believe that this review will lay the foundation for future reasonable structural design of oxide-based or even other types of superionic conductors, thus assisting in promoting the rapid development of alternative green and sustainable technologies.
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