Well-defined mesoporous MnO2 nanosheet arrays have been directly grown on Ni foam current collectors using one-step electrodeposition, followed by a low-temperature thermal annealing process. The ...as-deposited MnO2 nanosheets are 20–25 nm thick on average and are mesoporous with a pore size ranging from 2 to 8 nm. The potential for using these MnO2 nanosheet arrays as supercapacitor electrodes has been explored by cyclic voltammetry and galvanostatic charge/discharge tests within a potential window of 0–1.0 V versus saturated calomel electrode. The cyclic voltammograms of the MnO2 nanosheet electrode show a typical pseudocapacitive behavior. The nanosheets exhibit specific capacitance of 201, 150, 122, 105 and 96 F g−1 at current densities of 1, 5, 10, 15 and 20 A g−1, respectively. Furthermore, it is found that upon cycling at 5 A g−1, the specific capacitance loses 35% of its initial value in the beginning 1800 cycles and then remains constant up to 3000 cycles, showing reasonably good cycling performance. The electrochemical impedance spectroscopy demonstrates that the equivalent series resistance and charge transfer resistance of the electrode are very low, suggesting that the nickel foam supported MnO2 nanosheet array is a promising binder-free electrode for use in pseudocapacitors.
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•Porous MnO2 nanosheets are directly grown on Ni foam using one-step electrodeposition.•The binder-free MnO2 nanosheets/Ni foam electrode shows very low ESR and Rct.•The electrode exhibits high capacitance, good rate capability and long cycle life.
Self‐supported electrodes comprising carbon fiber paper (CP) integrated with bifunctional nickel phosphide (Ni‐P) electrocatalysts are fabricated by electrodeposition of Ni on functionalized CP, ...followed by a convenient one‐step phosphorization treatment in phosphorus vapor at 500 °C. The as‐fabricated CP@Ni‐P electrode exhibits excellent electrocatalytic performance toward hydrogen evolution in both acidic and alkaline solutions, with only small overpotentials of 162 and 250 mV, respectively, attaining a cathodic current density of 100 mA cm−2. Furthermore, the CP@Ni‐P electrode also exhibits superior catalytic performance toward oxygen evolution reaction (OER). An exceptionally high OER current of 50.4 mA cm−2 is achieved at an overpotential of 0.3 V in 1.0 m KOH. The electrode can sustain 10 mA cm−2 for 180 h with only negligible degradation, showing outstanding durability. Detailed microstructural and compositional studies reveal that upon OER in alkaline solution the surface Ni‐P is transformed to NiO covered with a thin Ni(OH)x layer, forming a Ni‐P/NiO/Ni(OH)x heterojunction, which presumably enhances the electrocatalytic performance for OER. Given the well‐defined bifunctionality, a full alkaline electrolyzer is constructed using two identical CP@Ni‐P electrodes as cathode and anode, respectively, which can realize overall water splitting with efficiency as high as 91.0% at 10 mA cm−2 for 100 h.
Overall water splitting is realized at a high efficiency (91.0% at 10 mA cm−2) with excellent stability and durability by an alkaline electrolyzer made from self‐supported carbon fiber paper electrodes integrated with bifunctional nickel phosphide catalysts. The self‐supported electrode exhibits superior electrocatalytic performance toward both hydrogen evolution and oxygen evolution reactions in alkaline medium.
Nickel phosphide is an emerging low‐cost, earth‐abundant catalyst that can efficiently reduce water to generate hydrogen. However, the synthesis of nickel phosphide catalysts usually involves ...multiple steps and is laborious. Herein, a convenient and straightforward approach to the synthesis of a three‐dimensional (3D) self‐supported biphasic Ni5P4‐Ni2P nanosheet (NS) array cathode is presented, which is obtained by direct phosphorization of commercially available nickel foam using phosphorus vapor. The synthesized 3D Ni5P4‐Ni2P‐NS array cathode exhibits outstanding electrocatalytic activity and long‐term durability toward the hydrogen evolution reaction (HER) in acidic medium. The fabrication procedure reported here is scalable, showing substantial promise for use in water electrolysis. More importantly, the approach can be readily extended to synthesize other self‐supported transition metal phosphide HER cathodes.
Hydrogen generation on self‐supported three‐dimensional nickel phosphide nanosheet array cathodes is reported. The nanosheets have been fabricated by direct phosphorization of commercial nickel foams using phosphorus vapor and show superior electrocatalytic activity and stability in acidic medium toward H2 generation.
Transition metal phosphides (TMPs) have recently emerged as a new class of pre-catalysts that can efficiently catalyze the oxygen evolution reaction (OER). However, how the OER activity of TMPs ...varies with the catalyst composition has not been systematically explored. Here, we report the alkaline OER electrolysis of a series of nanoparticulate phosphides containing different equimolar metal (M = Fe, Co, Ni) components. Notable trends in OER activity are observed, following the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP, which indicate that the introduction of a secondary metal(s) to a mono-metallic TMP substantially boosts the OER performance. We ascribe the promotional effect to the enhanced oxidizing power of bi- and tri-metallic TMPs that can facilitate the formation of MOH and chemical adsorption of OH
groups, which are the rate-limiting steps for these catalysts according to our Tafel analysis. Remarkably, the tri-metallic FeCoNiP pre-catalyst exhibits exceptionally high apparent and intrinsic OER activities, requiring only 200 mV to deliver 10 mA cm
and showing a high turnover frequency (TOF) of ≥0.94 s
at the overpotential of 350 mV.
Porous Co16S16O96 (COD database code: 591-0314) nanosheets have been fabricated by a simple and low-cost hydrothermal approach. The as-fabricated Co16S16O96 nanostructures are characterized by a ...porous interconnected sheet-like network and prove to be highly crystalline. Electrochemical tests reveal that the Co16S16O96 nanosheets can be reversibly charged and discharged in a potential window between −0.05 and 0.4 V vs. saturated calomel electrode at various specific current densities ranging from 0.5 A g−1 to 50 A g−1. The specific capacitance of these nanosheets is 333 F g−1 at 1 A g−1 in the beginning of cycling test, and increases with cycle numbers up to 386 F g−1, then remaining constant till 4000 cycles. More remarkably, even at a current density as high as 50 A g−1, the nanosheets still possess a specific capacitance of 170 F g−1, and only lose 15.3% of the initial capacitance value after 4000 cycles, showing great promise for use as high-performance supercapacitor electrodes.
•Facile synthesis of Co16S16O96 nanosheets – a new electrode material.•Co16S16O96 nanosheets exhibit high specific capacitance and good rate capability.•Co16S16O96 nanosheets show a long cycling life with high capacity retention.
The safety of CRISPR (clustered regularly interspaced short palindromic repeats)-based genome editing in the context of human gene therapy is largely unknown.
is a reasonable but not absolutely ...protective target for a cure of human immunodeficiency virus type 1 (HIV-1) infection, because
-null blood cells are largely resistant to HIV-1 entry. We transplanted CRISPR-edited
-ablated hematopoietic stem and progenitor cells (HSPCs) into a patient with HIV-1 infection and acute lymphoblastic leukemia. The acute lymphoblastic leukemia was in complete remission with full donor chimerism, and donor cells carrying the ablated
persisted for more than 19 months without gene editing-related adverse events. The percentage of CD4+ cells with
ablation increased by a small degree during a period of antiretroviral-therapy interruption. Although we achieved successful transplantation and long-term engraftment of CRISPR-edited HSPCs, the percentage of
disruption in lymphocytes was only approximately 5%, which indicates the need for further research into this approach. (Funded by the Beijing Municipal Science and Technology Commission and others; ClinicalTrials.gov number, NCT03164135.).
In the quest to develop next generation lithium ion battery anode materials, satisfactory electrochemical performance and low material/fabrication cost are the most desirable features. In this ...article, porous Si nanowires are synthesized by a cost‐effective metal‐assisted chemical etching method using cheap metallurgical silicon as feedstock. More importantly, a thin oxide layer (≈3 nm) formed on the surface of porous Si nanowires stabilizes the cycling performance of lithium ion batteries. Such an oxide coating is able to constrain the huge volume expansion of the underlying Si, yet it is thin enough to ensure good permeability for both lithium ions and electrons. Therefore, the extraordinary storage capacity of Si can be well retained in prolonged electrochemical cycles. Specifically, Si/SiOx nanowires deliver a reversible capacity of 1503 mAh g−1 at the 560th cycle at a current density of 600 mA g−1, demonstrating an average of only 0.04% drop per cycle compared with its initial capacity. Furthermore, the highly porous structure and thin Si wall facilitate the electrolyte penetration and shorten the solid‐state lithium transportation path, respectively. As a result, stable and satisfactory reversible capacities of 1297, 976, 761, 548, and 282 mAh g−1 are delivered at current densities of 1200, 2400, 3600, 4800, and 7200 mA g−1, respectively.
Porous Si/SiOx nanowires are synthesized by metal‐assisted chemical etching of a metallurgical silicon feedstock followed by a postannealing process. The oxide layer with appropriate thickness is able to accommodate the huge volume expansion of underlying Si, thus enhancing electrochemical performance. Therefore, an average of only 0.04% drop per cycle is recorded in a prolonged test of 560 cycles.
Nanoporous Pt−Co alloy nanowires were synthesized by electrodeposition of Co-rich Pt1Co99 alloy into anodic aluminum oxide (AAO) membranes, followed by a dealloying treatment in a mild acidic medium. ...These nanowires consist of porous skeletons with tiny pores of 1−5 nm and crystalline ligaments of 2−8 nm. Morphological and compositional evolutions of the porous Pt−Co nanowires upon dealloying were investigated, and their formation mechanism is discussed. The nanoporous Pt−Co alloy nanowires are found to exhibit distinctly enhanced electrocatalytic activities toward methanol oxidation as compared to the current state-of-the-art Pt/C and PtCo/C catalysts, thus showing substantial promise as efficient anode electrocatalysts in direct methanol fuel cells.
Resistive random-access memory devices with atomic layer deposition HfO
2
and radio frequency sputtering TiO
x
as resistive switching layers were fabricated successfully. Low-power characteristic ...with 1.52 μW set power (1 μA@1.52 V) and 1.12 μW reset power (1 μA@1.12 V) was obtained in the HfO
2
/TiO
x
resistive random-access memory (RRAM) devices by controlling the oxygen content of the TiO
x
layer. Besides, the influence of oxygen content during the TiO
x
sputtering process on the resistive switching properties would be discussed in detail. The investigations indicated that “soft breakdown” occurred easily during the electrical forming/set process in the HfO
2
/TiO
x
RRAM devices with high oxygen content of the TiO
x
layer, resulting in high resistive switching power. Low-power characteristic was obtained in HfO
2
/TiO
x
RRAM devices with appropriately high oxygen vacancy density of TiO
x
layer, suggesting that the appropriate oxygen vacancy density in the TiO
x
layer could avoid “soft breakdown” through the whole dielectric layers during forming/set process, thus limiting the current flowing through the RRAM device and decreasing operating power consumption.
Resistive switching processes in HfO2
are studied by electron holography and in situ energy‐filtered imaging. The results show that oxygen vacancies are gradually generated in the oxide layer under ...ramped electrical bias, and finally form several conductive channels connecting the two electrodes. It also shows that the switching process occurs at the top interface of the hafnia layer.
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