Science China Materials最新文献

Enhancing the catalytic activity of catalysts is a core objective in their design and synthesis processes, and the accessibility of active sites is one of the crucial factors determining catalyst activity. Polyoxometalate-based metal-organic complexes (POMOCs) with well-defined structures, which combine the advantages of POMs and MOCs, may offer the possibility to construct catalysts with highly accessible active sites. In this study, a series of POMOCs were successfully designed and synthesized using different POM templates, including [Co^II_1.5(L)_1.5(PMo₁₂O₄₀)(H₂O)₄]·3H₂O (Co-PMo₁₂), [Co^II_1.5(L)_1.5(PW₁₂O₄₀)(H₂O)₄]·3H₂O (Co-PW₁₂), [Co^II₂(L)₂-(SiW₁₂O₄₀)(H₂O)₄]·11H₂O (Co-SiW₁₂), and H[Co^II_2.5(L)₃-(P₂W₁₈O₆₂)(H₂O)₈]·10H₂O (Co-P₂W₁₈), which were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, and single crystal X-ray diffraction. The differences in catalytic activity among the four POMOCs for olefin epoxidation were attributed to the distinct accessibility of Co(II) sites upon thermal activation. Among them, Co-P₂W₁₈ achieved a remarkable 99% yield of 1,2-epox-ycyclooctane within 3 h at room temperature using O₂ as the oxidant, owing to its highly accessible unsaturated Co(II) sites. Co-P₂W₁₈ exhibits significantly superior catalytic activity for the cyclooctene epoxidation reaction compared to most reported catalysts. Additionally, the reaction mechanism was investigated using density functional theory.

P2-Na_0.67Ni_0.33Mn_0.67O₂ is highly expected to serve as a hopeful cathode for sodium-ion batteries, owing to its remarkable energy density and operating voltage. However, the severe phase transition of P2-O2 at high cut-off voltage induces large volume variation, which deteriorates the structure and leads to fast capacity decay. Over the past years, ion doping has been identified as an efficient way to suppress the phase transition, and a lot of attempts show the positive impact. Regrettably, concurrently achieving high capacity and high stability is still difficult work. In this work, we confirm that high capacity and high stability can be realized by precise composition regulation. The designed P2-Na_0.67Ni_0.28Mg_0.03-Fe_0.04Mn_0.55Ti_0.1O₂ maintaining the high electrochemical active element shows well suppressed phase transition, which contributes to outstanding structural stability and fast charge transfer kinetics. As a result, it shows a high specific capacity of 143.5 mAh g⁻¹ at 0.1 C, and operates with a long lifespan of 1000 cycles. This work demonstrates a new idea for concurrently realizing high capacity and stable cathode material by rationally structure design.

The high-value utilization of industrial wastes is critically important for environmental protection and the sustainable development of society. In this work, amorphous NaFeP₂O₇ (named NFPO) and NaFeP₂O₇/rGO (named NFPO/rGO) composite are synthesized via a selective chemical precipitation approach, utilizing the industrial jarosite residue as the iron source. The sodium storage performance and mechanism of this amorphous NFPO/rGO composite as a novel cathode material for sodium-ion batteries (SIBs) are explored for the first time. The as-synthesized amorphous NFPO/rGO composite exhibits outstanding long-term cycling performance of 79.1 mAh g⁻¹ after 1000 cycles at 0.1 A g⁻¹, while the crystalline NFPO/rGO composite does not work. Galvanostatic intermittent titration technique and in-situ electrochemical impedance spectroscopy analysis demonstrate that the amorphous NFPO/rGO composite has high Na⁺ diffusivity and fast kinetics. In-situ X-ray diffraction analysis reveals the structure change from amorphous NaFeP₂O₇ to triclinic Na₂FeP₂O₇ during the first discharge process and then evolves to a highly disordered structure in the subsequent charge/discharge cycles. The present work not only provides an avenue for the high-value utilization of jarosite residue but also offers theoretical guidance for the structural design and development of NaFeP₂O₇-based cathode materials for SIBs.

Dual-atom (DA) catalysts have exhibited great potential in regulating the catalytic performance of CO₂ reduction. However, there still exist huge challenges in the precise construction of DAs on a support. Herein, the precise immobilization of M-DAs (M = Ru, Rh, Pt) onto the Zr-oxo cluster of a 2D porphyrinic metal-organic framework (2D-Ni-PCN-222) was reported through a dimetallic complex pre-coordination strategy. The resultant M-DAs/2D-Ni-PCN-222 was applied in CO₂ photoreduction with ammonia borane as the H* donor. Under visible light, the optimal catalyst Ru-DAs/2D-Ni-PCN-222 displayed a HCOO⁻ production rate up to 35.4 mmol g⁻¹ h⁻¹ with nearly 100% selectivity and 691 h⁻¹ turnover frequency. Kinetic isotope experiments demonstrated that the coupling rate between H* and CO₂ governed the production efficiency of HCOO⁻. In situ experiments and density functional calculations disclosed that Ru-DAs with highly delocalized d electrons could accept the photo-generated electrons from 2D-Ni-PCN-222 and then inject to inert CO₂ molecules. Further ab initio molecular dynamics simulations revealed that the adaptive shortening of Ru–O coordination bonds during CO₂ adsorption played an important role in facilitating the deeper activation and the formation of optimal η³–O,C,O adsorption mode of the CO₂ molecule.

Corrosion is required for biodegradable metals during their clinical services, but it could also affect their mechanical performance and might even lead to premature failure. In particular, for some newly developed biodegradable metals like zinc-based alloys, their corrosion-associated mechanical behavior is of critical relevance, although it remains unclear. In this study, long-term corrosion/degradation-associated mechanical behavior of hot-extruded Zn-Cu and Zn-Cu-Fe alloys, two promising Zn-based bio-metals, was investigated from the perspective of load-bearing biomedical implants application, compared with pure Zn. The immersion degradation and mechanical assessments verified that the evolving corrosion profile of bio-metals governed their mechanical performance. Nonetheless, alloying with Cu and Fe turned out to be effective in mitigating this impact, as the grain-refined microstructure helps alleviate localized corrosion attacks compared to pure Zn. In addition, the evenly distributed fine second phases may work as a cathodic part of the galvanic coupling corrosion cells and therefore facilitate the uniform corrosion. Likewise, the presence of Cu and Fe helps to form more protective products against corrosion of the underlying Zn matrix. In short, the overall suppressed corrosion, especially the localized type, could reduce the susceptibility to stress concentration of Zn-based biodegradable metals (bio-metals), therefore delaying the mechanical decline and maintaining the structural integrity as long as desired. The findings not only provide new insights into better understanding the correlation between the degradation process and mechanical evolution of zinc-based bio-metals, but also raise concerns when developing new types of bio-metals for clinical translation.

Traditional optical fiber communication encryption methods lack sufficient dynamic adaptability and hardware flexibility, while reconfigurable logic gates can overcome this limitation, thereby significantly improving the flexibility of encryption systems. This study reports a reconfigurable optoelectronic logic gate (OELG) system based on hafnium-zirconium oxide (HZO) ferroelectric thin films. Through ultra-low temperature atomic layer deposition technique, the fabricated HZO thin films demonstrate an exceptional pyroelectric coefficient (1835.91 µC m⁻² K⁻¹) and robust multi-level polarization stability, enabling efficient broadband photon-to-current conversion. By leveraging the pyroelectric effect and tunable polarization states, the OELG device achieves dynamic optical signal modulation and logic processing. The OELG device supports five fundamental logic operations (AND, OR, NAND, NOR, NOT) via electrical bias and polarization control, without requiring hardware modifications. The OELG device demonstrates stable performance over 10⁹ cycles with no degradation, meeting practical application requirements. Furthermore, a convolutional neural network (CNN)-integrated image encryption-decryption framework was validated, achieving 95.01% recognition accuracy on decrypted data, while unauthorized decryption attempts resulted in significant feature loss. This study addresses security challenges in optical communication networks by proposing an innovative solution that integrates pyroelectric materials with reconfigurable logic gate technology, offering a new pathway to enhance physical-layer security.

Aprotic lithium-oxygen (Li-O₂) batteries are severely limited by slow cathode reaction kinetics and large polarization. Herein, we design and prepare a Mott-Schottky catalyst by uniformly embedding ultrafine Ru nanoparticles on the nitrogen-doped carbon (Ru@NC) nanoflakes to accelerate oxygen redox kinetics of Li-O₂ batteries. The Mott-Schottky effect of Ru@NC drives the spontaneous electron rearrangement in the NC matrix and induces a strong built-in electric field at heterointerfaces, which accelerates the activation and conversion of oxygen intermediates. The obtained Ru@NC possesses rich Mott-Schottky heterointerfaces and defective carbon structures, which provide extensive adsorption and nucleation sites. More importantly, Ru@NC manifests moderate affinity for the intermediate LiO₂, inducing formation of unique nanosheet-like Li₂O₂ with low Li₂O₂/cathode interfacial impedance, which further enhances oxidation kinetics. These enable the Li-O₂ battery with Ru@NC to deliver a remarkably reduced polarization of 0.89 V, superior rate performance, and prolonged lifespan of over 200 cycles. This work will provide valuable guidelines for engineering advanced electrocatalysts for high-performance Li-O₂ batteries and beyond.

Pore-tuning engineering has been proven as an effective strategy in catalyst design for energy storage and conversion. Herein, we propose a rhombic dodecahedral iron and nitrogen co-doped carbon-based material (Fe-N-C) with hierarchical micro-mesoporous structures using mesoporous silica as the pore template and iron launch vehicle. The as-prepared catalysts (m-Fe/NC) exhibit much boosted ORR activity with half-wave potential of 0.81 V and 0.88 V in acidic and alkaline media, respectively. Furthermore, a superior specific capacity of 815 mAh g_Zn⁻¹ and stable cell voltage of 1.31 V is achieved at current density of 10 mA cm⁻² when using m-Fe/NC as cathode for zinc-air batteries (ZAB). Advanced characterization techniques and theoretical calculations reveal that the introduction of mesopore structure not only improves the active site exposure, but also the proper curvature-induced strain effect from mesoporous concave surface enhances the intrinsic activity. This work provides significant insights for future development of innovative nanoporous electrocatalysts.

Organic light-emitting diodes (OLEDs) are an advanced technology used in full-color displays. These systems suffer from a main limitation, i.e., the low efficiency of blue OLEDs, and emitters are critical to solve this issue. Here, we developed a new strategy to design robust Pt(II) emitters with enhanced molecular rigidity and increased locally excited character. An obtained Pt(II) emitter exhibited an extremely narrow emission spectrum peaking at 458.6 nm, with a full-width at half-maximum (FWHM) of 16.0 nm and a small Huang-Rhys factor of 0.278, together with a high quantum efficiency of 95%. The emitter-doped OLED peaked at 464 nm with a high color purity (FWHM = 19 nm), and high external quantum efficiencies (EQEs) of 32.6%, 29.4%, and 26.9% at 123, 1000, and 5000 cd/m², respectively. The device also achieved a record-high maximum brightness of up to 84895 cd/m² among reported deep-blue OLEDs with Commission Internationale de l’Éclairage y-coordinate < 0.15. This device represents one of the highest-performing deep-blue OLEDs reported to date.

Light-emitting electrochemical cells (LECs), featuring simple device structures and low-cost solution processability, have garnered considerable attention for display and lighting applications, but they face challenges in achieving high efficiency and high color purity. Herein, we report two ionic multi-resonance (MR) emitters with narrowband blue emission for high-color-purity LECs, by covalently bonding an imidazolium functional group into a boron (B)/nitrogen (N)-doped polycyclic skeleton. This design not only maintains narrowband emission and high photoluminescence quantum yield (PLQY) of the MR skeleton, but also harnesses the functions of two kinds of N atoms (pyrrolic and pyridinic N atoms) within the imidazolium unit. On the one hand, the 1-position pyrrolic N atom with electron-rich character forms a para-B-π-N linkage with the MR skeleton, elevating the excited-state energy levels and blue-shifting the emission band. On the other hand, the 3-position pyridinic N atom provides a quaternization site to form intrinsically ionic emitters compatible with ionic hosts. Such emitters exhibit blue emission with narrow full-widths at half-maximum of 26–27 nm, and high PLQYs of 95%–97% in solid-state films. LECs based on these emitters exhibit narrowband blue emission with CIE coordinates of (0.12, 0.26) and a maximum external quantum efficiency of 4.6%, representing the first narrowband blue LECs based on intrinsically ionic MR emitters.