Search

Molten NaF-BeF 2 salt is widely considered a promising candidate to replace FLiBe in molten salt reactor applications, which is crucial to reducing the operating costs of the molten salt reactor. Studies on beryllium compounds are rarely conducted due to their volatility and high toxicity. Herein, the Be-F coordination structure of NaF/BeF 2 mixed salts was investigated in-depth through various HT-NMR and solid-state NMR methods, which are optimized to be appropriate for the detection of beryllium compounds. It was found that Na 2 BeF 4 and NaBeF 3 crystals were transformed into amorphous tetrahedral coordinated networks when there was an increase in the BeF 2 concentration in the mixed salts. The main coordinate structure comparisons between FNaBe and FLiBe were analyzed, which exhibit high similarity due to the covalent effect of Be-F bonding, demonstrating the theoretical feasibility of applying FNaBe salts as a substitute for FLiBe in MSR systems. In addition, the transition from the crystal phase to the amorphous phase occurred at a lower BeF 2 concentration for FNaBe than that for FLiBe. This was further verified by the results of ab initio molecular dynamics (AIMD) simulation that FNaBe melts had more disordered structures, thus causing slight changes in their physical properties., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Disclosing the roles of reactive sites at catalytic interfaces is of paramount importance for understanding the reaction mechanism. However, due to the difficulties in the detection of reaction intermediates in the complex heterophase reaction system, disentangling the highly convolved roles of different surface atoms remains challenging. Herein, we used CoO x as a model catalyst to study the synergy of Co Td 2+ and Co Oh 3+ active sites in the electrocatalytic oxygen evolution reaction (OER). The formation and evolution of reaction intermediates on the catalyst surface during the OER process were investigated by in situ surface-enhanced Raman spectroscopy (SERS). According to the SERS results in ion-substitution experiments, Co Oh 3+ is the catalytic site for the conversion of OH - to O-O - intermediate species (1140-1180 cm -1 ). CoOOH (503 cm -1 ) and CoO 2 (560 cm -1 ) active centers generated during the OER, at the original Co Td 2+ sites of CoO x , eventually serve as the O 2 release sites (conversion of O-O - intermediate to O 2 ). The mechanism was further confirmed on Co 2+ -Co 3+ layered double hydroxides (LDHs), where an optimal ratio of 1:1.2 (Co 2+ /Co 3+ ) is required to balance O-O - generation and O 2 release. This work highlights the synergistic role of metal atoms at different valence statuses in water oxidation and sheds light on surface component engineering for the rational design of high-performance heterogeneous catalysts.

Multi-wavelength lasers, especially the triple-wavelength laser around 1060 nm, could be produced by the 4 F 3/2 → 4 I 11/2 transition of Nd 3+ and present numerous challenges and opportunities in the field of optoelectronics. The Nd 3+ -doped high-temperature phase of LaBSiO 5 (β-LBSO) is an ideal crystal to produce triple-wavelength lasers; however, the crystal growth is challenging because of the phase transition from β-LBSO to low-temperature phase (α-LBSO) at 162 °C. This phase transition is successfully suppressed when the doping content of Nd 3+ is larger than 6.3 at. %, and the Nd 3+ -doped β-LBSO is stable at room temperature. The local disorder of BO 4 tetrahedra due to Nd 3+ doping is essential to the stabilization of β-LBSO. For the first time, the β-LBSO:8%Nd 3+ crystal with a dimension of 1.8 × 1.8 × 1.8 cm 3 is obtained through the top-seeded solution method. The crystal shows strong optical absorption in the range of 785-815 nm, matching well with the commercial laser diode pumping source. The optical emission of 4 F 3/2 → 4 I 11/2 splits into four peaks with the highest optical emission cross section of 2.14 × 10 -20 cm 2 at 1068 nm. The continuous-wave triple-wavelength generation of coherent light at 1047, 1071, and 1092 nm is achieved with the highest output power of 235 mW and efficiency of 12.1%.

It is fascinating yet challenging to assemble anisotropic nanowires into ordered architectures of high complexity and intriguing functions. We exploited a facile strategy involving oriented etching of a metal-organic fragment (MOF) to advance the rational design of highly ordered nanostructures. As a proof of concept, a microscale MIL-68(In) single crystal was etched with a K 3 [Co(CN) 6 ] solution to give a microtube composed of aligned MIL-68(In) nanorods. Annealing such a MIL-68(In) microtube readily created an unprecedented branched In 2 O 3 mesocrystal by assembly of In 2 O 3 nanorods aligned in order. The derived ordered-In 2 O 3 -ZnIn 2 S 4 is more efficient in catalyzing visible-light-driven H 2 evolution (8753 μmol h -1 g -1 ) outperforming the disordered-In 2 O 3 -ZnIn 2 S 4 counterpart (2700 μmol h -1 g -1 ) as well as many other state-of-the-art ZnIn 2 S 4 -based photocatalysts. The ordered architecture significantly boosts the short-range electron transfer in an In 2 O 3 -ZnIn 2 S 4 heterojunction but has a negligible impact on the long-range electron transfer among In 2 O 3 mesocrystals. The density functional theory (DFT) calculation reveals that the oriented etching is achieved by the selective binding of the [Co(CN) 6 ] 3- etchant on the (110) plane of MIL-68(In), which can drag the In atoms out of the framework in order. Our findings could broaden the technical sense toward advanced photocatalyst design and impose scientific impacts on unveiling how ordered photosystems operate.

Practical applications of lithium metal anodes are gravely impeded by inhomogeneous lithium deposition, which results in dendrite growth. Electrolyte additives are proven to be effective in improving performance but usually serve only a single function. Herein, nitrofullerene is introduced as a bifunctional additive with a smoothing effect and forms a protective solid electrolyte interphase (SEI) layer on stable lithium metal anodes. By design, nitro-C 60 can gather on electrode protuberances via electrostatic interactions and then be reduced to NO 2 - and insoluble C 60 . Next, the C 60 anchors on the uneven groove of the lithium surface, resulting in a homogeneous distribution of Li ions. Finally, NO 2 - anions can react with metallic Li to build a compact and stable SEI with high ion transport. With a 5 mM nitro-C 60 additive, Li-Li symmetric cells show superior cycle stability in both carbonate and ether electrolytes, Li-sulfur batteries with a high cathode loading (10.6 mg cm -2 , 6 mAh cm -2 ) can achieve improved cycle retention of 63.2% over 100 cycles in a carbonate electrolyte, and full cells paired with a high-areal-capacity LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode (3.5 mAh cm -2 ) exhibit a significantly enhanced cycle lifespan even under lean electrolyte conditions.

The rational design and controllable fabrication of electrode materials with tailored structures and superior performance is highly desirable for the next-generation lithium ion batteries (LIBs). In this work, a novel three-dimensional (3D) graphite foam (GF)@SnO 2 nanorod arrays (NRAs)@polyaniline (PANI) hybrid architecture was constructed via solvothermal growth followed by electrochemical deposition. Aligned SnO 2 NRAs were uniformly grown on the surface of GF, and a PANI shell with a thickness of ∼40 nm was coated on individual SnO 2 nanorods, forming a SnO 2 @PANI core-shell structure. Benefiting from the synergetic effect of 3D GF with large surface area and high conductivity, SnO 2 NRAs offering direct pathways for electrons and lithium ions, and the conductive PANI shell that accommodates the large volume variation of SnO 2 , the binder-free, integrated GF@SnO 2 NRAs@PANI electrode for LIBs exhibited high capacity, excellent rate capability, and good electrochemical stability. A high discharge capacity of 540 mAh g -1 (calculated by the total mass of the electrode) was achieved after 50 cycles at a current density of 500 mA g -1 . Moreover, the electrode demonstrated superior rate performance with a discharge capacity of 414 mAh g -1 at a high rate of 3 A g -1 .

An in situ simple and effective synthesis method is effectively exploited to construct MOF-derived grape-like architecture anchoring on nitrogen-doped graphene, in which ultrafine Fe3O4 nanoparticles are uniformly dispersed (Fe3O4@C/NG). In this hybrid hierarchical structure, new synergistic features are accessed. The graphene oxide plane with functional groups is expected to alleviate the aggregation problem in the MOFs' growth. Moreover, the morphology and size of iron-based MOFs and carbon content are conveniently controlled by controlling the solution concentration of precursor. Through making use of in situ carbonization of the organic ligands in MOFs, Fe3O4 subunits are effectively protected by 3D interconnected conductive carbon at microscale. Consequently, when applied as anode materials, even as high as 10 A g(-1) after 1000 cycles, Fe3O4@C/NG still maintains as high as 458 mA h g(-1).