International Journal of Minerals, Metallurgy, and Materials最新文献

Cobalt nanoparticles (NPs) catalysts are extensively used in heterogeneous catalytic reactions, and the addition of alkali metal promoters is a common method to modulate the catalytic performance because the catalyst’s surface structures and morphologies are sensitive to the addition of promoters. However, the underlying modulation trend remains unclear. Herein, the adsorption of alkali metal promoters (Na and K) on the surfaces of face-centered-cubic (FCC) and hexagonal-closest packed (HCP) polymorphous cobalt was systematically investigated using density functional theory. Furthermore, the effect of alkali promoters on surface energies and nanoparticle morphologies was revealed on the basis of Wulff theory. For FCC-Co, the exposed area of the (111) facet in the nanoparticle increases with the adsorption coverage of alkali metal oxide. Meanwhile, the (311), (110), and (100) facets would disappear under the higher adsorption coverage of alkali metals. For HCP-Co, the Wulff morphology is dominated by the (0001) and ((10bar 11)) facets and is independent of the alkali metal adsorption coverage. This work provides insights into morphology modulation by alkali metal promoters for the rational design and synthesis of cobalt-based nanomaterials with desired facets and morphologies.

The development of tin-based devices with low toxicity is critical for the commercial viability of perovskite solar cells. However, because tin halide is a stronger Lewis acid, its crystallization rate is extremely fast, resulting in the formation of numerous defects that affect the device performance of tin-based perovskite solar cells. Herein, propylamine hydrobromide (PABr) was added to the perovskite precursor solution as an additive to passivate defects and fabricate more uniform and dense perovskite films. Because propylamine cations are too large to enter the perovskite lattices, they only exist at the grain boundary to passivate surface defects and promote crystal growth in a preferred orientation. The PABr additive raises the average short-circuit current density from 19.45 to 25.47 mA·cm⁻² by reducing carrier recombination induced by defects. Furthermore, the device’s long-term illumination stability is improved after optimization, and the hysteresis effect is negligible. The addition of PABr results in a power conversion efficiency of 9.35%.

Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy. Complex preparation processes and poor repeatability are currently considered to be an insuperable impediment to the promotion of the large-scale production and application of electrocatalysts. Avoiding the use of intricate instruments, corrosion engineering is an intriguing strategy to reduce the cost and presents considerable potential for electrodes with catalytic performance. An anode comprising quinary AlCoCrFeNi layered double hydroxides uniformly decorated on an AlCoCrFeNi high-entropy alloy is proposed in this paper via a one-step corrosion engineering method, which directly serves as a remarkably active catalyst for boosting the oxygen evolution reaction (OER) in alkaline seawater. Notably, the best-performing catalyst exhibited oxygen evolution reaction activity with overpotential values of 272.3 and 332 mV to achieve the current densities of 10 and 100 mA·cm⁻², respectively. The failure mechanism of the obtained catalyst was identified for advancing the development of multicomponent catalysts.

Metal corrosion causes billions of dollars of economic losses yearly. As a smart and new energy-harvesting device, triboelectric nanogenerators (TENGs) can convert almost all mechanical energy into electricity, which leads to great prospects in metal corrosion prevention and cathodic protection. In this work, flexible TENGs were designed to use the energy harvested by flexible polydimethylsiloxane (PDMS) films with ZrB₂ nanoparticles and effectively improve the dielectric constant by incorporating ZrB₂. The open-circuit voltage and short-circuit current were 264 V and 22.9 µA, respectively, and the power density of the TENGs reached 6 W·m⁻². Furthermore, a self-powered anti-corrosion system was designed by the rectifier circuit integrated with TENGs, and the open-circuit potential (OCP) and Tafel curves showed that the system had an excellent anti-corrosion effect on carbon steel. Thus, the system has broad application prospects in fields such as metal cultural relics, ocean engineering, and industry.

Piezocatalysis has attracted unprecedented research interest as a newly emerging catalysis technology. However, the inherent insulating property of ferroelectric materials ultimately leads to the poor vibration–electricity conversion ability. Herein, this work reports the (K_0.52Na_0.48)NbO₃ ferroelectric ceramics (KNNFCx), for which the FeCo modification strategy is proposed. The substitution of the moderate amount of FeCo (x = 0.015) at Nb site not only optimizes ferroelectricity but also produces beneficial defects, notably increasing Rhodamine B water purification efficiency to 95%. The pinning effect of monovalent oxygen vacancies on ferroelectric domains is responsible for the excellent ferroelectric polarization of KNNFC0.015 through the generation of an internal field to promote charge carriers separation and reduce non-radiative recombination. Importantly, the accompanying electron carriers can easily move to the material surface and participate in redox reactions because they have low activation energy. Therefore, ferroelectric polarization and defects play synergetic roles in enhancing piezocatalytic performance.

The activation of CO on iron-based materials is a key elementary reaction for many chemical processes. We investigate CO adsorption and dissociation on a series of Fe, Fe₃C, Fe₅C₂, and Fe₂C catalysts through density functional theory calculations. We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites. The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst. The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C–O bond. We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models. We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations. Among them, a ridge linear regression model with 2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.

Reducing the cost and improving the electrocatalytic activity are the key to developing high efficiency electrocatalysts for oxygen evolution reaction (OER). Here, bimetallic NiFe-based metal-organic framework (MOF) was prepared by solvothermal method, and then used as precursor to prepare NiFe-based MOF-derived materials by pyrolysis. The effects of different metal ratios and pyrolysis temperatures on the sample structure and OER electrocatalytic performance were investigated and compared. The experimental results showed that when the metal molar ratio was Fe: Ni = 1:5 and the pyrolysis temperature was 450°C, the sample (FeNi₅-MOF-450) exhibits a composite structure of NiFe₂O₄/FeNi₃/C and owns the superior electrocatalytic activity in OER. When the current density is 100 mA·cm⁻², the overpotential of the sample was 377 mV with Tafel slope of 56.2 mV·dec⁻¹, which indicates that FeNi₅-MOF-450 exhibits superior electrocatalytic performance than the commercial RuO₂. Moreover, the long-term stability of FeNi₅-MOF-450 further promotes its development in OER. This work demonstrated that the regulatory methods such as component optimization can effectively improve the OER catalytic performance of NiFe-based MOF-derived materials.

All solid-state electrolytes have the advantages of good mechanical and thermal properties for safer energy storage, but their energy density has been limited by low ionic conductivity and large interfacial resistance caused by the poor Li⁺ transport kinetics due to the solid–solid contacts between the electrodes and the solid-state electrolytes. Herein, a novel gel polymer electrolyte (UPP-5) composed of ionic liquid incorporated metal-organic frameworks nanoparticles (IL@MOFs) is designed, it exhibits satisfying electrochemical performances, consisting of an excellent electrochemical stability window (5.5 V) and an improved Li⁺ transference number of 0.52. Moreover, the Li/UPP-5/LiFePO₄ full cells present an ultra-stable cycling performance at 0.2C for over 100 cycles almost without any decay in capacities. This study might provide new insight to create an effective Li⁺ conductive network for the development of all-solid-state lithium-ion batteries.

Na₃V₂(PO₄)₂O₂F (NVPOF) has received considerable interest as a promising cathode material for sodium-ion batteries because of its high working voltage and good structural/thermal stability. However, the sluggish electrode reaction resulting from its low intrinsic electronic conductivity significantly restricts its electrochemical performance and thus its practical application. Herein, Nb-doped Na₃V_2−xNb_x(PO₄)₂O₂F/graphene (rGO) composites (x = 0, 0.05, 0.1) were prepared using a solvothermal method followed by calcination. Compared to the un-doped NVPOF/rGO, doping V-site with high-valence Nb element (Nb⁵⁺) (Na₃V_1.95Nb_0.05(PO₄)₂O₂F/rGO (NVN05POF/rGO)) can result in the generated V⁴⁺/V³⁺ mixed-valence, ensuring the lower bandgap and thus the increased intrinsic electronic conductivity. Besides, the expanded lattice space favors the Na⁺ migration. With the structure feature where NVN05POF particles are attached to the rGO sheets, the electrode reaction kinetics is further accelerated owing to the well-constructed electron conductive network. As a consequence, the as-prepared NVN05POF/rGO sample exhibits a high specific capacity of ∼72 mAh·g⁻¹ at 10C (capacity retention of 65.2% (vs. 0.5C)) and excellent long-term cycling stability with the capacity fading rate of ∼0.099% per cycle in 500 cycles at 5C.