Carboxylic Acid Group-Induced Oxygen Vacancy Migration on an Anatase (101) Surface

Dye-sensitized solar cells (DSSCs) have aroused intensive interest for the replacement of conventional crystalline silicon solar cells. Through carboxylic acid groups, the dyes attach to the TiO₂ anatase (101) surface, on which the subsurface oxygen vacancies (Vo^subs) are predominant. The performance of DSSCs can be affected by the presence and positions of oxygen vacancies (Vos). By applying density functional theory calculations, we found that the adsorption of a carboxylic acid group-decorated dye molecule reverses the relative stability between the surface oxygen vacancy (Vo^surf) and Vo^sub on the anatase (101) surface, which facilitates the migration of the Vo from the subsurface to the surface by overcoming an energy barrier of less than 0.16 eV, which is significantly lower than the 1.01 eV energy barrier on the clean surface. Further, ab initio molecular dynamics simulations indicate that the Vo^sub can easily migrate to the surface at room temperature. This dynamic interplay between the Vo of the anatase (101) surface and the carboxylic acid group would be important for future studies concerning the stability and photovoltaic efficiency of the solar cells

Interface-Mediated Synthesis of Transition-Metal (Mn, Co, and Ni) Hydroxide Nanoplates

We report a general and efficient strategy to produce monodisperse transition-metal (Mn, Co, and Ni) hydroxide nanoplates with tunable composition through the interface-mediated growth process. It is worth noting that, using common nitrates as the precursors, the as-obtained nanoplates were prepared under hydrothermal conditions. Moreover, the possible formation mechanism of the transition-metal hydroxide nanoplates has also been investigated. Subsequently, the resulting transition-metal hydroxides can be eventually transformed into transition-metal oxide nanoplates and lithium-ion intercalation materials through solid-state reactions, respectively. Furthermore, the electrochemical properties of the resulting nanomaterials have also been discussed in detail. This protocol may be easily extended to fabricate many other metal hydroxide and oxide nanomaterials

Composition-Dependent Catalytic Activity of Bimetallic Nanocrystals: AgPd-Catalyzed Hydrodechlorination of 4‑Chlorophenol

Ag–Pd bimetallic nanocrystals (NCs) with tunable compositions and narrow size distributions were produced by a one-pot synthesis. The NC growth process was investigated by time-dependent TEM, XRD, and UV–vis studies. In the hydrodechlorination of 4-chlorophenol, the AgPd_<i>x</i> (<i>x</i> = 2, 4, 6, 9, 19) showed pronounced composition-dependent catalytic activities, leading to the AgPd₉ catalyst with excellent activity

Energy Upconversion in Lanthanide-Doped Core/Porous-Shell Nanoparticles

Here, we report upconversion nanoparticles with a core/porous-shell structure in which bulk emission and nanoemission are simultaneously observed. The activated porous shell can efficiently tune the bulk emission but has negligible influence on the nanoemission

Single-Crystalline Octahedral Au–Ag Nanoframes

We report the formation of single-crystalline octahedral Au–Ag nanoframes by a modified galvanic replacement reaction. Upon sequential addition of AgNO₃, CuCl, and HAuCl₄ to octadecylamine solution, truncated polyhedral silver nanoparticles formed first and then changed into octahedral Au–Ag nanoframes, without requiring a conventional Ag removal step with additional oxidation etchant. The nanoframes have 12 sides, and all of the eight {111} faces are empty. The side grows along the [110] direction, and the diameter is less than 10 nm. The selective gold deposition on the high-energy (110) surface, the diffusion, and the selective redeposition of Au and Ag atoms are the key reasons for the formation of octahedral nanoframes

Construction of S‑modified Amorphous Fe(OH)₃ on NiSe Nanowires as Bifunctional Electrocatalysts for Efficient Seawater Splitting

Seawater electrolysis is valuable for hydrogen production, but there are significant challenges such as severe Cl– corrosion and competition reaction of the chlorine evolution reaction (CER) due to high Cl– concentrations. Here, a core–shell structure was developed on the nickel foam substrate, consisting of a sulfur-modified amorphous Fe(OH)3 layer on top of a crossing NiSe nanowire (named S–Fe(OH)3/NiSe/NF). The S–Fe(OH)3/NiSe/NF electrode demonstrates outstanding catalytic performance for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in simulated and natural alkaline seawater electrolytes. The overpotentials at 100 mA/cm2 for the OER in simulated and natural alkaline seawater electrolytes are 234 and 232 mV, respectively. For HER, the values are 331 and 341 mV, respectively, at a current density of 100 mA/cm2. When S–Fe(OH)3/NiSe/NF serves as both the anode and cathode, the electrolyzer demonstrates excellent performance with voltages of 1.85 and 1.87 V at 100 mA/cm2 in simulated and natural seawater electrolytes, respectively. This electrolyzer holds significant promise for practical seawater electrolysis

Syntheses of Water-Soluble Octahedral, Truncated Octahedral, and Cubic Pt–Ni Nanocrystals and Their Structure–Activity Study in Model Hydrogenation Reactions

We developed a facile strategy to synthesize a series of water-soluble Pt, Pt_<i>x</i>Ni_1‑<i>x</i> (0 < <i>x </i>< 1), and Ni nanocrystals. The octahedral, truncated octahedral, and cubic shapes were uniformly controlled by varying crystal growth inhibition agents such as benzoic acid, aniline, and carbon monoxide. The compositions of the Pt_<i>x</i>Ni_1‑<i>x</i> nanocrystals were effectively controlled by choice of ratios between the Pt and Ni precursors. In a preliminary study to probe their structure–activity dependence, we found that the shapes, compositions, and capping agents strongly influence the catalyst performances in three model heterogeneous hydrogenation reactions

Crystal Orientation Tuning of LiFePO₄ Nanoplates for High Rate Lithium Battery Cathode Materials

We report the crystal orientation tuning of LiFePO₄ nanoplates for high rate lithium battery cathode materials. Olivine LiFePO₄ nanoplates can be easily prepared by glycol-based solvothermal process, and the largest crystallographic facet of the LiFePO₄ nanoplates, as well as so-caused electrochemical performances, can be tuned by the mixing procedure of starting materials. LiFePO₄ nanoplates with crystal orientation along the <i>ac</i> facet and <i>bc</i> facet present similar reversible capacities of around 160 mAh g^–1 at 0.1, 0.5, and 1 C-rates but quite different ones at high C-rates. The former delivers 156 mAh g^–1 and 148 mAh g^–1 at 5 C-rate and 10 C-rate, respectively, while the latter delivers 132 mAh g^–1 and only 28 mAh g^–1 at 5 C-rate and 10 C-rate, respectively, demonstrating that the crystal orientation plays important role for the performance of LiFePO₄ nanoplates. This paves a facile way to prepare high performance LiFePO₄ nanoplate cathode material for lithium ion batteries

Nanoscale Coating of LiMO₂ (M = Ni, Co, Mn) Nanobelts with Li⁺‑Conductive Li₂TiO₃: Toward Better Rate Capabilities for Li-Ion Batteries

By using a novel coating approach based on the reaction between MC₂O₄·<i>x</i>H₂O and Ti­(OC₄H₉)₄, a series of nanoscale Li₂TiO₃-coated LiMO₂ nanobelts with varied Ni, Co, and Mn contents was prepared for the first time. The complete, thin Li₂TiO₃ coating layer strongly adheres to the host material and has a 3D diffusion path for Li⁺ ions. It is doped with Ni²⁺ and Co³⁺ ions in addition to Ti⁴⁺ in LiMO₂, both of which were found to favor Li⁺-ion transfer at the interface. As a result, the coated nanobelts show improved rate, cycling, and thermal capabilities when used as the cathode for Li-ion battery

Preparation and Photoelectrochemical Properties of CdSe/TiO₂ Hybrid Mesoporous Structures

We report on the design and synthesis of a novel CdSe/TiO₂ hybrid mesoporous structure and its implementation as a photoanode for photoelectrochemical (PEC) application. The CdSe/TiO₂ hybrid mesoporous structure was produced by assembling CdSe quantum dots (QDs) and TiO₂ nanocrystals into CdSe/TiO₂ hybrid colloidal spheres, followed by calcination to remove the capping ligands between CdSe and TiO₂. Compared to the system involving CdSe QDs directly linked to TiO₂ through molecular linkers, this CdSe/TiO₂ hybrid mesoporous structure affords the advantage of better interfacial coupling between CdSe and TiO₂ due to closer contact. As a result, the CdSe/TiO₂ hybrid mesoporous structure exhibits significantly improved photoresponse as a photoanode, as demonstrated successfully in comparative PEC studies. This study illustrates the importance of fundamental structural control in influencing PEC properties of hybrid assembled nanostructures