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1. Orthogonal deposition of Au on different facets of Ag cuboctahedra for the fabrication of nanoboxes with complementary surfaces

   https://doi.org/10.1039/c9nr08420g  

   Ahn, Jaewan; Kim, Junki; Qin, Dong (January 2020, Nanoscale)

   We report the fabrication of Ag–Au cuboctahedral nanoboxes enclosed by {100} and {111} facets, respectively, through the orthogonal deposition of Au on two different facets of Ag cuboctahedra. Specifically, we titrate aqueous HAuCl 4 into an aqueous mixture containing Ag cuboctahedra, ascorbic acid, and NaOH (under basic conditions), in the presence of poly(vinylpyrrolidone) (PVP) and cetyltrimethylammonium chloride (CTAC), respectively. In the case of PVP, the oxidation of Ag was initiated from the {111} facets of the cuboctahedra through the galvanic replacement reaction between Au( iii ) and Ag, accompanied by the deposition of Au onto the {100} facets. Because the dissolved Ag( i ) ions could react with NaOH to form Ag 2 O on the {111} facets and thus terminate the galvanic reaction, the Au( iii ) ions would be further reduced by the ascorbate monoanion (HAsc − ) to generate Au atoms for their continuing deposition on the {100} facets, converting Ag cuboctahedra to Ag@Au {100} cuboctahedra. Upon the etching of Ag from the core, we obtained Ag–Au cuboctahedral nanoboxes enclosed by {100} facets. In contrast, when CTAC was present, the oxidation of Ag through a galvanic reaction could continuously proceed on {100} facets as the dissolved Ag( i ) ions would react with the excessive amount of Cl − ions derived from CTAC to produce soluble AgCl 2 − ions rather than insoluble Ag 2 O. As a result, the dissolved Ag( i ) and Au( iii ) ions would be co-reduced by HAsc − for the generation of Ag and Au atoms, followed by their co-deposition onto {111} facets for the generation of Ag@Au {111} concave cuboctahedra. After the removal of Ag from the core by etching, we obtained Ag–Au {111} cuboctahedral nanoboxes enclosed by {111} facets. Both samples of cuboctahedral nanoboxes exhibited strong optical absorption in the infrared region. Interestingly, the cuboctahedral nanoboxes enclosed by {111} facets showed significantly enhanced catalytic activity toward the reduction of 4-nitrophenol by NaBH 4 relative to their counterparts encased by {100} facets. 

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2. Facet-dependent Catalysis of CuNi Nanocatalysts toward 4–Nitrophenol Reduction Reaction

   https://doi.org/10.1557/adv.2020.5  

   Li, Can; Luan, Yiliang; Zhao, Bo; Kumbhar, Amar; Chen, Xiaobo; Collins, David; Zhou, Guangwen; Fang, Jiye (January 2020, MRS Advances)

   ABSTRACT We report a facile method to fabricate CuNi nano-octahedra and nanocubes using a colloidal synthesis approach. The CuNi nanocrystals terminated with exclusive crystallographic facets were controlled and achieved by a group of synergetic capping ligands in a hot solution system. Specifically, the growth of {111}-bounded CuNi nano-octahedra is derived by a thermodynamic control, whereas the generation of {100}-terminated CuNi nanocubes is steered by a kinetic capping of chloride. Using a reduction of 4-nitrophenol with sodium borohydride as a model reaction, CuNi nano-octahedra and nanocubes demonstrated a strong facet-dependence due to their different surface energies although both exhibited remarkable catalytic activity with the high rate constant over mass (k/m). A kinetic study indicated that this is a pseudo first-order reaction with an excess of sodium borohydride. CuNi nanocubes as the catalysts showed better catalytic performance (k/m = 385 s -1 •g -1 ) than the CuNi nano-octahedra (k/m = 120 s -1 •g -1 ), indicating that 4-nitrophenol and hydrogen were adsorbed on the {100} facets with their molecules parallel to the surface much easier than those on {111} facets. 

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3. High-temperature creep of magnetite and ilmenite single crystals

   https://doi.org/10.1007/s00269-020-01122-6  

   Till, J. L.; Rybacki, E. (December 2020, Physics and Chemistry of Minerals)

   null (Ed.)

   Abstract We performed deformation experiments on dry natural single crystals of magnetite and ilmenite to determine the rheological behavior of these oxide minerals as a function of temperature, orientation, and oxygen fugacity. Samples were deformed at temperatures of 825–1150  $$\,^{\circ }$$ ∘ C to axial strains of up to 15–24% under approximately constant stress conditions up to 120 MPa in a dead-load-type creep rig at ambient pressure in a controlled gas atmosphere. Oxygen fugacity ranged from 10 $$^{-9.4}$$ - 9.4 to 10 $$^{-4}$$ - 4 atm. Ilmenite creep was insensitive to oxygen fugacity, while magnetite displayed a strong, non-monotonic oxygen fugacity dependence, with creep rates varying as $$f_{O_{2}}^{-0.7}$$ f O 2 - 0.7 and $$f_{O_{2}}^{0.4}$$ f O 2 0.4 at more reducing and more oxidizing conditions, respectively. Dislocation creep rates of magnetite single crystals were weakly dependent on crystallographic orientation with stress exponents that varied between 2.8 and 4.3 (mean 3.5 ± 0.4). Magnetite compressed parallel to <100>, <110>, and <111> axes exhibited apparent activation energies of 315±5, 345±30, and 290±5 kJ/mol, respectively. We estimated $${f_O}_2$$ f O 2 -independent magnetite activation energies of 715 ± 150, 725 ± 145, and 690 ± 150 kJ/mol for <100>, <110>, and <111> orientations, respectively, in the region of negative $${f_O}_2$$ f O 2 -dependence. Ilmenite single crystals were compressed parallel, normal, and inclined to the c-axis. Stress exponents of 3.4, 4.3, and 3.9 indicate dislocation creep with activation energies of 420 ± 35, 345 ± 30, and 360 ± 40 kJ/mol, respectively, for these orientations. Mechanical anisotropy in ilmenite is notably higher than in magnetite, as expected from its lower crystal symmetry. Constitutive equations were formulated for ilmenite and magnetite creep. 

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4. Electrochemical Nitrate Reduction with Low-Index Cu Single Crystals: Selectivity Trends in Alkaline Solution

   https://doi.org/10.1021/jacs.6c05147  

   Phillips, William T; Bi, Hongshan; Vasilijević, Anastasija; Doyle, Owen P; Lin, Zhou; DuChene, Joseph S (July 2026, Journal of the American Chemical Society)

   Sargent, Edward (Ed.)

   Electrochemical nitrate (NO3−) reduction is a promising pathway toward the production of ammonia (NH3). While copper (Cu) electrodes are commonly used for this reaction, the influence of Cu surface structure on reaction selectivity is poorly understood. Here, we performed electrochemical NO3− reduction in alkaline electrolytes with Cu(100), Cu(110), and Cu(111) single-crystal electrodes and quantified the product distributions across a range of applied potentials. Our systematic study of electrocatalytic NO3− reduction demonstrated that the Cu(100) and Cu(110) surfaces exhibited similar selectivity and rates for NH3 production, but the Cu(100) surface provided >95% Faradaic efficiency toward NH3 over the broadest range of applied potentials. In contrast, the Cu(111) surface was significantly less selective for NH3 production. Further comparing the electrochemical behavior of Cu single crystals to their corresponding product distributions revealed that nitrite (NO2−) reduction voltammograms were strong predictors of electrocatalytic performance for all three low-index Cu surfaces in alkaline electrolytes. Quantum mechanical calculations indicate that the Cu(100) surface exhibits the lowest potential-determining step for NO3− reduction to NH3, supporting our experimental findings. Detailed analysis of metal−adsorbate interactions also revealed the role of Cu surface structure in stabilizing key reaction intermediates to promote selective NH3 production. Our combined experimental and computational study establishes electrocatalytic selectivity of low-index Cu facets for NH3 synthesis and offers practical guidelines for the design of Cu-based electrocatalysts capable of selective electrochemical NO3− reduction in alkaline solutions. 

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5. Size-tuned Pt–Ni octahedra for enhanced oxygen reduction reaction performance

   https://doi.org/10.1557/s43580-026-01639-y  

   Delgado, Joseph; Li, Can; Zhao, Bo; Bharathan, Prabhu; Maryam, Areesha; Fang, Jiye (April 2026, MRS Advances)

   Abstract Pt-Ni octahedral nanocrystals with exposed {111} facets are highly active oxygen reduction reaction (ORR) catalysts, yet achieving precise control over their particle size remains challenging. In this work, three Pt-Ni octahedral nanocatalysts with tunable sizes were synthesized using a one-pot colloidal method by adjusting the amount of NiCl₂·6H₂O precursor. Interestingly, both decreasing and increasing the Ni precursor amount relative to the standard value of 0.05 mmol resulted in smaller octahedra. At low precursor concentrations, limited Ni precursor supply restricts crystal growth, whereas at high concentrations, accelerated nucleation and Cl⁻-induced stabilization of the (111) facets inhibit further growth. Electrochemical measurements show that the catalyst exhibiting the smallest particle size delivers the highest ORR mass activity (1.98 A/mg_Pt), likely due to its large specific surface area. This work highlights the crucial role of precursor concentration in tailoring nanoparticle dimensions and enhancing the electrochemical activity of Pt-Ni catalysts for the ORR. Graphical abstract 

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