Author: Bimetallic platinum–nickel (Pt–Ni) alloys as oxygen reduction reaction (ORR) electrocatalysts show genuine potential to boost widespread use of low-temperature fuel cells in vehicles by virtue of their high catalytic activity. However, their practical implementation encounters primary challenges in structural and catalytic durability caused by the low formation heat of Pt–Ni alloys. Here, we report nanoporous (NP) (Pt1–xNix)3Al intermetallic nanoparticles as oxygen electroreduction catalyst NP (Pt1–xNix)3Al, which circumvents this problem by making use of the extraordinarily negative formation heats of Pt–Al and Ni–Al bonds. The NP (Pt1–xNix)3Al nanocatalyst, which is mass-produced by alloying/dealloying and mechanical crushing technologies, exhibits specific activity of 3.6 mA cm–2Pt and mass activity of 2.4 A mg–1Pt at 0.90 V as a result of both ligand and compressive strain effects, while strong Ni–Al and Pt–Al bonds ensure their exceptional durability by alleviating evolution of Pt, Ni, and Al components and dissolutions of Ni and Al atoms.Keywords: dealloying; electrocatalysis; fuel cells; intermetallic compounds; nanoporous metals; oxygen reduction reaction; platinum alloys;

Transition-metal oxides show genuine potential in replacing state-of-the-art carbonaceous anode materials in lithium- or sodium-ion batteries because of their much higher theoretical capacity. However, they usually undergo massive volume change, which leads to numerous problems in both material and electrode levels, such as material pulverization, instable solid-electrolyte interphase, and electrode failure. Here, it is demonstrated that lithium-ion breathable hybrid electrodes with 3D architecture tackle all these problems, using a typical conversion-type transition-metal oxide, Fe3O4, of which nanoparticles are anchored onto 3D current collectors of Ni nanotube arrays (NTAs) and encapsulated by δ-MnO2 layers (Ni/Fe3O4@MnO2). The δ-MnO2 layers reversibly switch lithium insertion/extraction of internal Fe3O4 nanoparticles and protect them against pulverizing and detaching from NTA current collectors, securing exceptional integrity retention and efficient ion/electron transport. The Ni/Fe3O4@MnO2 electrodes exhibit superior cyclability and high-capacity lithium storage (retaining ≈1450 mAh g−1, ≈96% of initial value at 1 C rate after 1000 cycles).

Transition-metal hydroxides (TMHOs) or oxides (TMOs) with layered crystalline structures are attractive electrode materials for high-density charge storage in electrochemical supercapacitors. However, their randomly stacked nanostructures on conductive reinforcements, typically carbon materials, exhibit only modest enhancement of rate capability because of poor electron and ion transports that are limited by highly anisotropic conductivity, excessive grain boundaries and weak TMHO or TMO/C interfaces. Here we report a hybrid electrode design to tackle all three of these problems in layered Ni(OH)2 for high-performance asymmetric supercapacitors, wherein the single-crystalline Ni(OH)2 nanosheets are vertically aligned on a three-dimensional bicontinuous nanoporous gold skeleton with epitaxial Au/Ni(OH)2 interfaces (NP Au/VA Ni(OH)2). As a result of the unique nanoarchitecture, the pseudocapacitive behavior of Ni(OH)2 is dramatically enhanced for ensuring a volumetric capacitance as high as ∼2911 F cm−3 (∼2416 F g−1 for the constituent Ni(OH)2) in the NP Au/VA Ni(OH)2 electrode with excellent rate capability. Asymmetric supercapacitors assembled with this NP Au/VA Ni(OH)2 electrode and activated carbon have a high gravimetric energy of 31.4 W h kg−1 delivered at an exceptionally high power density of 100 kW kg−1 with excellent cycling stability.

Monolayer tungsten disulfide (WS2), a typical member of the semiconducting transition metal dichalcogenide family, has drawn considerable interest because of its unique properties. Intriguingly, the edge of WS2 exhibits an ideal hydrogen binding energy, which makes WS2 a potential alternative to Pt-based electrocatalysts for the hydrogen evolution reaction (HER). Here, we demonstrate for the first time the successful synthesis of uniform monolayer WS2 nanosheets on centimeter-scale Au foils using a facile, low-pressure chemical vapor deposition method. The edge lengths of the universally observed triangular WS2 nanosheets are tunable from ∼100 to ∼1,000 nm. The WS2 nanosheets on Au foils featuring abundant edges were then discovered to be efficient catalysts for the HER, exhibiting a rather high exchange current density of ∼30.20 μA/cm2 and a small onset potential of ∼110 mV. The effects of coverage and domain size (which correlate closely with the active edge density of WS2) on the electrocatalytic activity were investigated. This work not only provides a novel route toward the batch-production of monolayer WS2 via the introduction of metal foil substrates but also opens up its direct application for facile HER.

There is a strong interest in plasmonic nanostructures that uniformly enhance Raman signals of chemical and biological molecules using surface-enhanced Raman spectroscopy (SERS) for trace detection. Although the resonant excitation of localized surface plasmons of single or assembled metallic nanoparticles can generate large electromagnetic fields, their SERS effects suffer from poor reproducibility and uniformity, limiting their highly reliable and stable applications. Here, we report self-supported large-scale nanoporous hybrid films with high density and uniform hot spots, produced by the implantation of SnO nanoparticles into nanoporous Au/Ag bimetallic films (NP Au/SnO/Ag) for the trace detections of both resonant and non-resonant molecules. The NP Au/SnO/Ag films exhibit extraordinary SERS enhancements, which increase with the increasing density of Au/SnO/Ag sandwich protrusions, as a result of the formation of abundant and uniform hot spots. The nanogaps in their wrinkled films further improve the capability to detect molecules at single molecular levels, making the hybrid films promising SERS-active substrates with superior reproducibility and reliability for applications in life science and environment protection.

Nanostructured SnO2 is an attractive anode material for high-energy-density lithium-ion batteries because of the fourfold higher theoretical charge capacity than commercially used graphite. However, the poor capacity retention at high rates and long-term cycling have intrinsically limited applications of nanostructured SnO2 anodes due to large polarization and ∼300% volume change upon lithium insertion/extraction. Here we report the design of a SnO2-based anode, which is constructed by embedding SnO2 nanoparticles into a seamlessly integrated 3D nanoporous/solid copper current collector (S/NP Cu/SnO2), with an aim at tackling both problems for the high-performance reversible lithium storage. As a result of the unique hybrid architecture that enhances electron transfer and rapid access of the lithium ion into the particle bulk, the S/NP Cu/SnO2 anode can store charge with a capacity density as high as ∼3695 mA h cm−3 and an exceptional rate capability. Even when the discharge rate is increased by a factor of 160 (12 A g−1), it still retains ∼1178 mA h cm−3, one order of magnitude higher than that of a traditional SnO2-based electrode (∼111.6 mA h cm−3), which is assembled by mixing SnO2 nanoparticles with conductive carbon black and a polymeric binder and coating on flat Cu foil. In addition, not only do the rigid Cu skeleton and the stable Cu/SnO2 interface improve the microstructural stability, but also the pore channels accommodate the large SnO2 volume changes, enlisting the S/NP Cu/SnO2 anode to exhibit high specific capacity over 1000 cycles at a high rate.

Au nanostructures as catalysts toward electrooxidation of small molecules generally suffer from ultralow surface adsorption capability and stability. Here, we report Ni(OH)2 layer decorated nanoporous (NP) AuNi alloys with a three-dimensional and bimodal porous architecture, which are facilely fabricated by a combination of chemical dealloying and in situ surface segregation, for the enhanced electrocatalytic performance in biosensors. As a result of the self-grown Ni(OH)2 on the AuNi alloys with a coherent interface, which not only enhances adsorption energy of Au and electron transfer of AuNi/Ni(OH)2 but also prohibits the surface diffusion of Au atoms, the NP composites are enlisted to exhibit significant enhancement in both electrocatalytic activity and stability toward glucose electrooxidation. The highly reliable glucose biosensing with exceptional reproducibility and selectivity as well as quick response makes it a promising candidate as electrode materials for the application in nonenzymatic glucose biosensors.Keywords: biosensor; electrooxidation; nanoporous gold; nickel hydrate

Controllable synthesis of monolayer MoS2 is essential for fulfilling the application potentials of MoS2 in optoelectronics and valleytronics, etc. Herein, we report the scalable growth of high quality, domain size tunable (edge length from ∼200 nm to 50 μm), strictly monolayer MoS2 flakes or even complete films on commercially available Au foils, via low pressure chemical vapor deposition method. The as-grown MoS2 samples can be transferred onto arbitrary substrates like SiO2/Si and quartz with a perfect preservation of the crystal quality, thus probably facilitating its versatile applications. Of particular interest, the nanosized triangular MoS2 flakes on Au foils are proven to be excellent electrocatalysts for hydrogen evolution reaction, featured by a rather low Tafel slope (61 mV/decade) and a relative high exchange current density (38.1 μA/cm2). The excellent electron coupling between MoS2 and Au foils is considered to account for the extraordinary hydrogen evolution reaction activity. Our work reports the synthesis of monolayer MoS2 when introducing metal foils as substrates, and presents sound proof that monolayer MoS2 assembled on a well selected electrode can manifest a hydrogen evolution reaction property comparable with that of nanoparticles or few-layer MoS2 electrocatalysts.Keywords: Au foil; chemical vapor deposition; hydrogen evolution reaction; molybdenum disulfide; thickness control;

Nanostructured SnO2 is an attractive anode material for high-energy-density lithium-ion batteries because of the fourfold higher theoretical charge capacity than commercially used graphite. However, the poor capacity retention at high rates and long-term cycling have intrinsically limited applications of nanostructured SnO2 anodes due to large polarization and ∼300% volume change upon lithium insertion/extraction. Here we report the design of a SnO2-based anode, which is constructed by embedding SnO2 nanoparticles into a seamlessly integrated 3D nanoporous/solid copper current collector (S/NP Cu/SnO2), with an aim at tackling both problems for the high-performance reversible lithium storage. As a result of the unique hybrid architecture that enhances electron transfer and rapid access of the lithium ion into the particle bulk, the S/NP Cu/SnO2 anode can store charge with a capacity density as high as ∼3695 mA h cm−3 and an exceptional rate capability. Even when the discharge rate is increased by a factor of 160 (12 A g−1), it still retains ∼1178 mA h cm−3, one order of magnitude higher than that of a traditional SnO2-based electrode (∼111.6 mA h cm−3), which is assembled by mixing SnO2 nanoparticles with conductive carbon black and a polymeric binder and coating on flat Cu foil. In addition, not only do the rigid Cu skeleton and the stable Cu/SnO2 interface improve the microstructural stability, but also the pore channels accommodate the large SnO2 volume changes, enlisting the S/NP Cu/SnO2 anode to exhibit high specific capacity over 1000 cycles at a high rate.

There is a strong interest in plasmonic nanostructures that uniformly enhance Raman signals of chemical and biological molecules using surface-enhanced Raman spectroscopy (SERS) for trace detection. Although the resonant excitation of localized surface plasmons of single or assembled metallic nanoparticles can generate large electromagnetic fields, their SERS effects suffer from poor reproducibility and uniformity, limiting their highly reliable and stable applications. Here, we report self-supported large-scale nanoporous hybrid films with high density and uniform hot spots, produced by the implantation of SnO nanoparticles into nanoporous Au/Ag bimetallic films (NP Au/SnO/Ag) for the trace detections of both resonant and non-resonant molecules. The NP Au/SnO/Ag films exhibit extraordinary SERS enhancements, which increase with the increasing density of Au/SnO/Ag sandwich protrusions, as a result of the formation of abundant and uniform hot spots. The nanogaps in their wrinkled films further improve the capability to detect molecules at single molecular levels, making the hybrid films promising SERS-active substrates with superior reproducibility and reliability for applications in life science and environment protection.

Transition-metal hydroxides (TMHOs) or oxides (TMOs) with layered crystalline structures are attractive electrode materials for high-density charge storage in electrochemical supercapacitors. However, their randomly stacked nanostructures on conductive reinforcements, typically carbon materials, exhibit only modest enhancement of rate capability because of poor electron and ion transports that are limited by highly anisotropic conductivity, excessive grain boundaries and weak TMHO or TMO/C interfaces. Here we report a hybrid electrode design to tackle all three of these problems in layered Ni(OH)2 for high-performance asymmetric supercapacitors, wherein the single-crystalline Ni(OH)2 nanosheets are vertically aligned on a three-dimensional bicontinuous nanoporous gold skeleton with epitaxial Au/Ni(OH)2 interfaces (NP Au/VA Ni(OH)2). As a result of the unique nanoarchitecture, the pseudocapacitive behavior of Ni(OH)2 is dramatically enhanced for ensuring a volumetric capacitance as high as ∼2911 F cm−3 (∼2416 F g−1 for the constituent Ni(OH)2) in the NP Au/VA Ni(OH)2 electrode with excellent rate capability. Asymmetric supercapacitors assembled with this NP Au/VA Ni(OH)2 electrode and activated carbon have a high gravimetric energy of 31.4 W h kg−1 delivered at an exceptionally high power density of 100 kW kg−1 with excellent cycling stability.