Pseudo-binary layered compound IVVI-V₂VI₃ families show great promise for application in thermoelectrics. Herein, through introducing iodine in GeSb₂Te₄, several synergistic effects come into being and contribute to outstanding thermoelectric performance. The I^Te donor-like defects suppress the hole carrier concentration from 5.72 × 10²⁰ cm⁻³ to 2.80 × 10²⁰ cm⁻³. First-principles calculations reveal that iodine doping increases the band gap from 0.253 eV to 0.302 eV and contributes to valence band convergence. Seebeck coefficient value reaches up to 135.7 μV/K at 773 K, and the power factor values are entirely boosted in the whole temperature region, reaching a maximum value of 12.4 μW·cm⁻¹·K⁻² in GeSb₂Te_3.96I_0.04. Moreover, iodine doping simultaneously reduces the lattice and electronic thermal conductivity, leading to the greatly reduced total thermal conductivity from 2.89 W·m⁻¹·K⁻¹ in pristine sample to 0.89 W·m⁻¹·K⁻¹ in GeSb₂Te_3.84I_0.16 at 323 K. Finally, a maximum zT ~1.12 at 773 K and an average zT ~0.62 over 323–773 K are achieved in GeSb₂Te_3.88I_0.12. This work puts forward an effective strategy to synergistically optimize phonon and carrier transport properties of pseudo-binary compounds through halogen doping, which may be effective in other similar material systems.

Metal nanowires show promise in a broad range of applications and can be fabricated via a number of methods, such as vapor–liquid–solid process and template-based electrodeposition. However, the synthesis of Al nanowires (NWs) is still challenging from the stable alumina substrate. In this work, the Ni-catalyzed fabrication of Al NWs has been realized using various Al₂O₃ substrates. The growth dynamics of Al NWs on Ni/Al₂O₃ was studied using in situ transmission electron microscopy (TEM). The effect of alumina structures, compositions, and growth temperature were investigated. The growth of Al NWs correlates with the Na addition to the alumina support. Since no eutectic mixture of nickel aluminide was formed, a mechanism of Ni-catalyzed reduction of Al₂O₃ for Al NWs growth has been proposed instead of the vapor–liquid–solid mechanism. The key insights reported here are not restricted to Ni-catalyzed Al NWs growth but can be extended to understanding the dynamic change and catalytic performance of Ni/Al₂O₃ under working conditions.

Fuel cells operated with a reformate fuel such as methanol are promising power systems for portable electronic devices due to their high safety, high energy density and low pollutant emissions. However, several critical issues including methanol crossover effect, CO-tolerance electrode and efficient oxygen reduction electrocatalyst with low or non-platinum usage have to be addressed before the direct methanol fuel cells (DMFCs) become commercially available for industrial application. Here, we report a highly active and selective Mg−Co dual-site oxygen reduction reaction (ORR) single atom catalyst (SAC) with porous N-doped carbon as the substrate. The catalyst exhibits a commercial Pt/C-comparable half-wave potential of 0.806 V (versus the reversible hydrogen electrode) in acid media with good stability. Furthermore, practical DMFCs test achieves a peak power density of over 200 mW cm⁻² that far exceeds that of commercial Pt/C counterpart (82 mW cm⁻²). Particularly, the Mg−Co DMFC system runs over 10 h with negligible current loss under 10 M concentration methanol work condition. Experimental results and theoretical calculations reveal that the N atom coordinated by Mg and Co atom exhibits an unconventional d-band-ditto localized p-band and can promote the dissociation of the key intermediate *OOH into *O and *OH, which accounts for the near unity selective 4e⁻ ORR reaction pathway and enhanced ORR activity. In contrast, the N atom in SAC–Co remains inert in the absorption and desorption of *OOH and *OH. This local coordination environment regulation strategy around active sites may promote rational design of high-performance and durable fuel cell cathode electrocatalysts.

Lead-free bismuth-based halide perovskites and their analogues have attracted research interest for their high stability and optoelectronic properties. However, the morphology-controlled synthesis of bismuth-based perovskite nanocrystals has been rarely demonstrated. Herein, we report the colloidal synthesis of zero-dimensional (0D) Cs₃BiCl₆ nanosheets (NSs), Cs₃Bi₂Cl₉ NSs/nanoplates (NPs) and Cs₄MnBi₂Cl₁₂ NPs through a hot-injection method. We demonstrate that the Cs₃BiCl₆ NSs, as an initial product of Cs₃Bi₂Cl₉ and Cs₄MnBi₂Cl₁₂ NPs, can transform into Cs₃Bi₂Cl₉ NSs or Cs₄MnBi₂Cl₁₂ NPs via Cl-induced metal ion insertion reactions under the templating effect of Cs₃BiCl₆. This growth mechanism is also applicable for the synthesis of Cs₄CdBi₂Cl₁₂ nanoplates. Furthermore, the alloying of Cd²⁺ into Cs₄MnBi₂Cl₁₂ lattice could weaken the strong coupling effect between Mn and Mn, which leads to a prolonged photoluminescence lifetime and an enhanced photoluminescence quantum yield (PLQY). As a proof of concept, the alloyed Cs₄Mn_xCd_1–xBi₂Cl₁₂ NPs are used as a scintillator, which show a lowest detection limit of 134.5 nGy/s. The X-ray imaging results display a high spatial resolution of over 20 line pairs per millimeter (lp/mm). These results provide new insights in the synthesis of anisotropic bismuth-based perovskite nanocrystals and their applications in radiation detection.

Hydrogen energy is a resuscitated clean energy source and its sensitive detection in air is crucial due to its very low explosive limit. Metal oxide decorated with noble metal nanoparticles has been used for the enhancement of gas detection and exhibits superior sensitivity. Understanding the intrinsic mechanism of the detection and the enhancement mechanism is thus becoming a fundamental issue for the further development of novel metal/oxide compound gas-sensing materials. However, the correlation between the microstructural evolution, the charge transport and the complex sensing process has not yet been directly revealed and its atomic mechanism is still debatable. In this study, an Au/WO_2.7 compound was synthesized and exhibited a strongly enhanced gas sensitivity to many reductive gases, especially H₂. Aberration-corrected environmental transmission electron microscopy was used to investigate the atomic-scale microstructural evolution in situ during the reaction between H₂ and Au/WO_2.7 compound. Swing and sintering processes of the Au particles on the WO_2.7 surface were observed under heating and gaseous environments, and no injection of hydrogen atoms was suggested. First principle calculations verified the swing and sintering processes, and they can be explained by the enhancement of H₂ sensitivity.