Science China Materials最新文献

Hydrogen peroxide that is produced through the two-electron pathway during the catalysis of oxygen reduction reaction (ORR) is recognized as harmful to the stability of nitrogen-doped carbon and Fe-based nonprecious catalyst (Fe-N-C) for fuel cell application. A major remaining scientific question is how fast the removal of these deleterious intermediates can contribute to stability enhancement. Here, we report that the stability of Fe-N-C catalysts is positively correlated with the kinetic constant of hydrogen peroxide decomposition. Modulation of the H₂O₂ decomposition kinetics by applying the frequency factor of the Arrhenius equation from 800 to 30000 s⁻¹ for TiO₂, CeO₂ and ZrO₂ reduced the decay rate of Fe-N-C catalysts from 0.151% to −0.1% in a 100-hour stability test. Fe-N-C/ZrO₂ with a frequency factor of 30000 s⁻¹ showed a 10% increase in current density during a 100-hour stability test and almost no decay during 15 hours of continuous fuel cell operation at a high potential of 0.7 V.

The inherent tumor microenvironment (TME) of hypoxia and high glutathione (GSH) hinders the production of reactive oxygen species (ROS), yet which are crucial roles to make the oxygen-independent chemodynamic therapy (CDT) outstanding. Herein, we constructed hyaluronic acid (HA)-modified and peroxymonosulfate (PMS)-loaded hollow manganese dioxide (HMn) nanoparticles for not only TME-response drug release but also the distinct ROS donors to strengthen CDT. Upon enriched in the tumor site, the prepared nanotheranostic agent (HA@HMn/PMS) depleted local GSH to reduce MnO₂ to Mn²⁺, followed by generating •OH and •SO₄⁻ through Fenton-like reaction and activation of PMS, respectively. The bring in of •SO₄⁻, a rare radical possessing exceptional oxidizing ability and oxygen-independent property, breaks the limitations of traditional ROS and causes serious damage to tumor cells. In a xenograft mouse tumor model, detailed studies demonstrated that HA@HMn/PMS can significantly inhibit tumor growth. This work inspires the enormous potential of CDT in investigating the application of multifunctional nanosystems by combining the consumption of GSH and the synergistic effect of multiple radicals in oncotherapy.

The advances in transmission electron microscopy (TEM) have greatly improved the characterization of heterogeneous catalysts, offering valuable insights into their operational efficacy through the correlation of their physico-chemical characteristics with performance, specificity, and robustness at nanoscales. Understanding tangible catalyst attributes and corresponding catalytic processes necessitates the identification and rationalization of catalyst behavior modifications during reaction conditions. Recent innovations in in-situ TEM techniques have opened new avenues to observe the progress of heterogeneous catalysis with unparalleled spatial precision, superior energy resolution, and precise temporal resolution in controlled or realistic catalytic environments. Herein, we have reviewed the established and evolving techniques for monitoring catalysts through the utilization of in-situ TEM. By combining in-situ TEM with cutting-edge spectroscopic methodologies like atomic electron tomography (AET), 4D-STEM, cryogenic electron microscopy, and monochromated electron energy loss spectroscopy (EELS), a comprehensive approach to catalyst observation is achieved. Likewise, this advancement is expected to highlight and expand the crucial role of in-situ TEM in elucidating catalyst surface structures, active sites, and reaction pathways across key catalytic reactions, shaping the field of research in heterogeneous catalysis. Finally, the potential applications, advantages, and challenges of using in-situ TEM are emphasized and addressed in detail.

Lead-halide perovskite single crystal (SC) heterojunctions have attracted significant attention for X-ray detection owing to their unique combination of high sensitivity, resolution, stability and low detection limit. However, the toxicity of lead in those perovskite heterojunctions limits their practical applications. Herein, we report the construction of the first all-inorganic lead-free Cs₂AgBiBr₆/Cs₃Bi₂Br₉ SC heterojunctions with an area of 20 × 20 mm² via a facile liquid-phase epitaxial method through temperature-lowering crystallization. The epitaxial crystallization of the three-dimensional (3D) Cs₂AgBiBr₆ SC film on a 2D Cs₃Bi₂Br₉ SC substrate requires a large driving force for transitioning from the Volmer–Weber mode to the layer-by-layer growth mode under a rapid cooling rate. The Cs₂AgBiBr₆/Cs₃Bi₂Br₉ SC heterojunction detector achieves a high sensitivity of 1390 µC Gy_air⁻¹ cm⁻² for 100 keV hard X-ray detection at room temperature, which is enhanced to 2075 µC Gy_air⁻¹ cm⁻² at 75°C, demonstrating impressive high-temperature stability. Moreover, the detector achieves a detection limit of 37.48 nGy_air s⁻¹ and excellent stability for 90 days without any encapsulation. This work demonstrates the feasibility of using the epitaxial mechanism of perovskite formation on a high-surface-energy substrate for the controllable construction of a 3D/2D heterojunction that significantly enhances X-ray detection performance.

Smart materials with tunable multiple-color emissions have been widely investigated in the fields of bioimaging, display, and information encryption. Herein, multicolor emissive molecules with hydrazone bridged triphenylamines and pyridinium groups are reported. The protonation of the pyridine subunit by various acids leads to aggregation-induced emission with broad emission colors ranging from blue to red in multiple states and spectra of λ_PL, dichloromethane solution = 463–584 nm, λ_PL,powder = 455–620 nm, and λ_PL,crystal = 485–657 nm, respectively. Upon grinding or heating, hydrazone with CF₃COO⁻ exhibit blue-shift emissions from red to yellow due to weakened molecular packing and conformational rigidity. In contrast, hydrazone with (CF₃SO₂)₂N⁻ exhibited redshift emission from green to yellow due to the decreased electron-donating ability of the triphenylamine unit upon transformation from a rigid pyramidal shape to a planar structure. These are rare, charged organic examples exhibiting predictable mechanochromic and thermochromic strong emissions through facile anion exchanges, potentially providing new insights into the design of smart materials.

Molybdenum-based catalysts have demonstrated significant potential in the electrocatalytic hydrogen evolution reaction (HER). However, the limited exposure of active sites and strong hydrogen adsorption result in suboptimal performance. Herein, a Mo₂N–MoSe₂ heterojunction is prepared on carbon cloth (MNS/CC) to enhance the HER. The strong electronic interaction between Mo₂N and MoSe₂, combined with the lower work function of Mo₂N, creates an intrinsic electric field at the heterojunction interface, which markedly improves charge transfer efficiency. Additionally, the optimized electronic structure of Mo sites further enhances charge transfer and intrinsically catalytic activity in HER. As a result, MNS/CC requires overpotentials of mere 65 and 210 mV to achieve current densities of 20 mA cm⁻² and 1 A cm⁻², respectively, with a Tafel slope of only 96 mV dec⁻¹. Moreover, MNS/CC maintains stable operation at 1 A cm⁻² for 240 h without significant degradation. The results offer insights into the design of non-precious metal-based electro-catalysts for industrial hydrogen production.

Colloids are a vital component of perovskite precursor solutions (PPSs), significantly influencing the quality of perovskite film formation. Despite their importance, a comprehensive understanding of these colloids remains elusive. In this work, we explored the colloidal compositions of two distinct PPS types: the monomer-mixing dissolution (MMD) and the pre-synthesized perovskite single crystal redissolution (SCR). We have uncovered a new dissolution chemical equilibrium mechanism where the transition from mixed monomers to the 3C cubic phase (α-phase) involves a reversible transformation. Our findings indicate that although colloidal size significantly affects the nucleation during perovskite crystallization, the composition of the colloids plays a more crucial role. The MMD method yields poly Pb-I·solvent clusters while the colloids derived from the SCR approach produce hexagonal lead-halide-based perovskite phase clusters. These divergent colloidal compositions lead to markedly different impacts on the perovskite film formation process. Notably, hexagonal-phase colloids act as favorable nucleation sites, promoting the generation of the α-phase perovskite films with larger grains, more homogeneous phases, and fewer defects. This work demonstrates the importance of tailoring colloidal compositions and provides theoretical insights into the beneficial effects of redissolving perovskite in forms such as powder, microcrystals, and single crystals.

The A-D-A′-D-A-type non-fused ring electron acceptors (NFREAs), consisting of electron-donating unit (D) as the bridge to link electron-accepting units (A and A′), have emerged as promising electron acceptors for organic solar cells (OSCs) and organic photodetectors (OPDs). As the units are linked by the carbon-carbon single bonds, these electron acceptors generally possess feasible synthesis and tunable optoelectronic properties. Herein, the recent progress of A-D-A′-D-A-type NFREAs is reviewed, including molecular design, device performance, structure-property relationships, and their applications in OSCs and OPDs. Finally, we discuss the challenges and propose the perspectives for the further development of A-D-A′-D-A-type NFREAs.