Ultrathin Wall (1 nm) and Superlong Pt Nanotubes with Enhanced Oxygen Reduction Reaction Performance

Microwave heating-assisted synthesis of ultrathin platinum-based trimetallic nanosheets as highly stable catalysts towards oxygen reduction reaction in acidic medium

There are currently almost no ternary platinum-based nanosheets used for acidic oxygen reduction reactions (ORR) due to the difficulty in synthesizing ternary nanosheets with high Pt content. In this work, several ultrathin platinum-palladium-copper nanosheets (PtPdCu NSs) with a thickness of around 1.90 nm were prepared via a microwave heating-assisted method. Microwave heating allows a large number of Pt atoms to deposit into PdCu nanosheets, forming Pt-based ternary nanosheets with high Pt content. Among them, Pt38Pd50Cu12 NSs catalyst displays the highest mass activity (MA) measured in 0.1 M HClO4 of 0.932 A/mgPt+Pd which is 8.6 times of that Pt/C. Besides, Pt38Pd50Cu12 NSs catalyst also exhibits excellent stability with an extremely low MA attenuation after 80,000 cycles accelerated durability testing (ADT) tests. In the single cell tests, the Pt38Pd50Cu12 NSs catalyst manifests higher maximum power density of 796 mW cm-2 than Pt/C of 606 mW cm-2. Density functional theory (DFT) calculations indicate the weaker adsorption between Pt and O-species in Pt38Pd50Cu12 NSs leads to a significant enhancement of ORR activity. This study provides a new strategy to design and prepare ultrathin Pt-based trimetallic nanosheets as efficient and durable ORR catalysts.

Cotton-derived three-dimensional carbon fiber aerogel with hollow nanocapsules and ultrahigh adsorption efficiency in dynamic sewage treatment system

An ultralight 3D carbon fiber aerogel with good flexibility is developed via soaking cotton in water and then calcinating at a high temperature. This cotton-derived carbon material is constituted by amorphous carbon and retains slight oxygen-containing groups. Besides, a lot of hollow carbon nanocapsules are yielded on the inside surface, resulting in abundant micropores and mesopores. Systemic investigations explore the molecular transformation from cotton to carbon fiber, and the formation of carbon nanocapsules. In the adsorption process for methyl orange (MO), this carbon fiber aerogel exhibits both a rapid adsorption rate and the ultrahigh adsorbability of 862.9 mg/g, outclassing most of carbon materials reported. Therefore, a dynamic sewage treatment system is built and consecutively removes hydrosoluble pollution for a long-term running time. For the cotton-derived carbon fiber aerogel, the good mechanical flexibility, excellent adsorption property, and high stability jointly provide a vast application prospect in future industrial wastewater remediation.

In situ electrochemical synthesis of Pd aerogels as highly efficient anodic electrocatalysts for alkaline fuel cells

Improving the utilization of noble metals is extremely urgent for fuel cell electrocatalysis, while three-dimensional hierarchical noble metal aerogels with abundant sites and channels are proposed to reinforce their electrocatalytic performances and decrease their amounts. Herein, novel Pd aerogels with tunable surface chemical states were prepared through a facile in situ electrochemical activation, starting with PdO x aerogels by the hydrolysis method. The hierarchical porous Pd aerogels showed unprecedented high activity towards the electrocatalytic oxidation of fuels including methanol (2.99 A mgPd -1), ethanol (8.81 A mgPd -1), and others in alkali, outperforming commercial catalysts (7.12- and 13.66-fold, corresponding to methanol and ethanol). Theoretical investigation unveiled the hybrid surface states with metallic and oxidized Pd species in Pd aerogels to regulate the adsorption of intermediates and facilitate the synergistic oxidation of adsorbed *CO, resulting in enhanced activity with the MOR as the model. Therefore, efficient Pd aerogels through the in situ electrochemical activation of PdO x aerogels were proposed and showed great potential for fuel cell anodic electrocatalysis.

Versatile nanoarchitectonics of Pt with morphology control of oxygen reduction reaction catalysts

Electro-catalytic activity of Pt in the oxygen reduction reaction (ORR) depends strongly on its morphology. For an understanding of how morphology affects the catalytic properties of Pt, the investigation of Pt materials having well-defined morphologies is required. However, the challenges remain in rational and facile synthesis of Pt particles with tuneable well-defined morphology. A promising approach for the controlled synthesis of Pt particles is 'self-assembly of building blocks'. Here, we report a unique synthesis method to control Pt morphology by using a self-assembly route, where nanoflower, nanowire, nanosheet and nanotube morphologies of Pt particles have been produced in a controlled manner. In the growth mechanism, Pt nanoparticles (5-11 nm) are rapidly prepared by using NaBH₄ as a reductant, followed by their agglomeration promoted by adding 1,2-ethylenediamine. The morphology of the resulting Pt particles can be easily controlled by tuning hydrophobic/hydrophilic interactions by the addition of isopropanol and H₂O. Of the Pt particles prepared using this method, Pt nanotubes show the highest ORR catalytic activity in an acid electrolyte with an onset potential of 1.02 V vs. RHE.

Advances in wearable textile-based micro energy storage devices: structuring, application and perspective

The continuous expansion of smart microelectronics has put forward higher requirements for energy conversion, mechanical performance, and biocompatibility of micro-energy storage devices (MESDs). Unique porosity, superior flexibility and comfortable breathability make the textile-based structure a great potential in wearable MESDs. Herein, a timely and comprehensive review of this field is provided according to recent research advances. The following aspects, device construction of textile-based MESDs (TMESDs), fabric processing of textile components and smart functionalization (e.g., mechanical reliability, energy harvesting, sensing, self-charging and self-healing, etc.) are discussed and summarized thoroughly. Also, the perspectives on the microfabrication processes and multiple applications of TMESDs are elaborated.

Spiny Pd/PtFe core/shell nanotubes with rich high-index facets for efficient electrocatalysis

The performance of fuel-cell related electrocatalysis is highly dependent on the morphology, size and composition of a given catalyst. In terms of rational design of Pt-based catalyst, one-dimensional (1D) ultrafine Pt alloy nanowires (NWs) are considered as a commendable model for enhanced catalysis on account of their favorable mass/charge transfer and structural durability. However, in order to achieve the noble metal catalysts in higher efficiency and lower cost, building high-index facets and shaping hollow interiors should be integrated into 1D Pt alloy NWs, which has rarely been done so far. Here, we report the first synthesis of a class of spiny Pd/PtFe core/shell nanotubes (SPCNTs) constructed by cultivating PtFe alloy branches with rich high-index facets along the 1D removable Pd supports, which is driven by the galvanic dissolution of Pd substrates concomitant with Stranski-Krastanov (S-K) growth of Pt and Fe, for achieving highly efficient fuel-cells-related electrocatalysis. This new catalyst can even deliver electrochemical active surface area (ECSA) of 62.7 m² g_Pt^-1, comparable to that of commercial carbon-supported Pt nanoparticles. With respect to oxygen reduction catalysis, the SPCNTs showcase the remarkable mass and specific activity of 2.71 A mg^-1 and 4.32 mA cm^-2, 15.9 and 16.0 times higher than those of commercial Pt/C, respectively. Also, the catalysts exhibit extraordinary resistance to the activity decay and structural degradation during 50,000 potential cycles. Moreover, the SPCNTs serve as a category of efficient and stable catalysts towards anodic alcohol oxidation.

Novel Nanofluidic Cells Based on Nanowires and Nanotubes for Advanced Chemical and Bio-Sensing Applications

Since the first introduction of one-dimensional nanochannels for single-molecule detection, there has been increasing interest in modern nanofluidic systems, such as chemical and biological sensing applications. Recently developed nanowires (NWs) and nanotubes (NTs) have received tremendous attention due to their unique geometrical, physical and chemical properties, which are very attractive in this field. Here, we review the recent research activities in the field of novel nanofluidic cells based on NWs and NTs. First, we give a brief introduction of this field. Then the common synthesis methods of NWs and NTs are summarized. After that, we discuss the working principle and sensing mechanism of nanofluidic devices, which is fundamental to the interaction between these nanostructures and small molecules. Finally, we present the NW- and NT-based devices for chemical and bio-sensing applications, such as gas sensing, pathogen detection, DNA sequencing, and so forth.

Atomic PdAu Interlayer Sandwiched into Pd/Pt Core/Shell Nanowires Achieves Superstable Oxygen Reduction Catalysis

Rationally designing the core/shell architecture of Pt-based electrocatalysts has been demonstrated as an effective way to induce a surface strain effect for promoting the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode of fuel cells. However, unstable core dissolution and structural collapse usually occur in Pt-based core/shell catalysts during the long-term cycling operation, greatly impacting actual fuel cell applications. Impeding the dissolution of cores beneath the Pt shells is the key to enhancing the catalytic stability of materials. Herein, a method for sandwiching atomic PdAu interlayers into one-dimensional (1D) Pd/Pt core/shell nanowires (NWs) is developed to greatly boost the catalytic stability of subnanometer Pt shells for ORR. The Pd/PdAu/Pt core/shell/shell NWs display only 7.80% degradation of ORR mass activity over 80 000 potential cycles with no dissolution of Pd cores and good preservation of the holistic sandwich core/shell nanostructures. This is a significant improvement of electrocatalytic stability compared with the Pd/Pt core/shell NWs, which deformed and inactivated over 80 000 potential cycles. The density functional theory (DFT) calculations further demonstrate that the electron-transfer bridge Pd and electron reservoir Au, serving in the PdAu atomic interlayer, both guarantee the preservation of the high electroactivity of surface Pt sites during the long-term ORR stability test. In addition, the Pd/PdAu/Pt NWs show a 1.7-fold higher mass activity (MA) for ORR than the conventional Pd/Pt NWs. The enhanced activity can be attributed to the strong interaction between PdAu interlayers and subnanometer-Pt shells, which suppresses the competitive Pd-4d bands and boosts the surface Pt-5d bands toward the Fermi level for higher electroactivity, proved from DFT.

Rapid synthesis of hollow PtPdCu trimetallic octahedrons at room temperature for oxygen reduction reactions in acid media

Hollow PtPdCu trimetallic octahedrons were prepared under mild conditions, exhibiting enhanced activity toward the oxygen reduction reaction in acid media.

Recent Advances on Controlled Synthesis and Engineering of Hollow Alloyed Nanotubes for Electrocatalysis

The past decade has witnessed great progress in the synthesis and electrocatalytic applications of 1D hollow alloy nanotubes with controllable compositions and fine structures. Hollow nanotubes have been explored as promising electrocatalysts in the fuel cell reactions due to their well-controlled surface structure, size, porosity, and compositions. In addition, owing to the self-supporting ability of 1D structure, hollow nanotubes are capable of avoiding catalyst aggregation and carbon corrosion during the catalytic process, which are two other issues for the widely investigated carbon-supported nanoparticle catalysts. It is currently a great challenge to achieve high activity and stability at a relatively low cost to realize commercialization of these catalysts. An overview of the structural and compositional properties of 1D hollow alloy nanotubes, which provide a large number of accessible active sites, void spaces for electrolytes/reactants impregnation, and structural stability for suppressing aggregation, is presented. The latest advances on several strategies such as hard template and self-templating methods for controllable synthesis of hollow alloyed nanotubes with controllable structures and compositions are then summarized. Benefiting from the advantages of the unique properties and facile synthesis approaches, the capability of 1D hollow nanotubes is then highlighted by discussing examples of their applications in fuel-cell-related electrocatalysis. Finally, the remaining challenges and potential solutions in the field are summarized to provide some useful clues for the future development of 1D hollow alloy nanotube materials.

Ternary Heterostructural Pt/CNx/Ni as a Supercatalyst for Oxygen Reduction

We report here a supercatalyst for oxygen reduction of Pt/CNx/Ni in a unique ternary heterostructure, in which the Pt and the underlying Ni nanoparticles are separated by two to three layers of nitrogen-doped carbon (CNx), which mediates the transfer of electrons from the inner Ni to the outer Pt and protects the Ni against corrosion at the same time. The well-engineered low-Pt catalyst shows ∼780% enhanced specific mass activity or 490% enhanced specific surface activity compared with a commercial Pt/C catalyst toward oxygen reduction. More importantly, the exceptionally strong tune on the Pt by the unique structure makes the catalyst superbly stable, and its mass activity of 0.72 A/mgPt at 0.90 V (well above the US Department of Energy's 2020 target of 0.44 A/mgPt at 0.90 V) after 50,000 cyclic voltammetry cycles under acidic conditions is still better than that of the fresh commercial catalyst.