Nickel nanoparticles encapsulated in few‐layer nitrogen‐doped graphene (Ni@NC) are synthesized by using a Ni‐based metal–organic framework as the precursor for high‐temperature annealing treatment. ...The resulting Ni@NC materials exhibit highly efficient and ultrastable electrocatalytic activity toward the hydrogen evolution reaction and the oxygen evolution reaction as well as overall water splitting in alkaline environment.
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•Development of cathodic plasma driven self-assembly approach.•Fabrication of 3D dendrites arranged by HEAs nanoparticles.•High OER performed induced from the large surface and ...lattice deformation of electrode.
High-entropy alloys (HEAs) have been recognized as promising catalysts enabling the improvement of the sluggish kinetics of oxygen evolution reaction (OER). Nevertheless, the fabrication of nano HEAs at large-scale is still challenging. Herein, for the first time to the best of our knowledge, cathodic plasma electrolysis deposition (CPED) is utilized to develop FeCoNiMnCu HEA dendrites which are self-assembled by single HEA nanoparticles. These particles were examined to be face-centered cubic, having a size less than 40 nm and being randomly stacked together porously. The dendrites appear a 3D structure and leave a gap of approximately 5 um in between, leading to a significantly large surface area. Along with the highly deformed lattices with defects, this unique nanostructure achieves the very high efficient OER performance with an overpotential of 280 mV at 10 mA cm−2 and a low Tafel slope of 59 mV dec−1 in 1.0 M KOH solution. FeCoNiMnCu HEA dendrites also show outstanding electrochemical stability and are claimed that no compositional reorganization occurs after the long-term durability test. This work provides a new route to synthesize nanoscale HEAs for energy storage and conversion in a large-scale base for practical commercialization.
We demonstrate an efficient core–shell GaAs/AlGaAs nanowire photodetector operating at room temperature. The design of this nanoscale detector is based on a type-I heterostructure combined with a ...metal–semiconductor–metal (MSM) radial architecture, in which built-in electric fields at the semiconductor heterointerface and at the metal/semiconductor Schottky contact promote photogenerated charge separation, enhancing photosensitivity. The spectral photoconductive response shows that the nanowire supports resonant optical modes in the near-infrared region, which lead to large photocurrent density in agreement with the predictions of electromagnetic and transport computational models. The single nanowire photodetector shows a remarkable peak photoresponsivity of 0.57 A/W, comparable to large-area planar GaAs photodetectors on the market, and a high detectivity of 7.2 × 1010 cm·Hz1/2/W at λ = 855 nm. This is promising for the design of a new generation of highly sensitive single nanowire photodetectors by controlling the optical mode confinement, bandgap, density of states, and electrode engineering.
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The two-dimensional semiconductor photocatalytic material has excellent photocatalytic H2 evolution activity. In order to further improve the hydrogen production activity of g-C3N4, ...this study improved the preparation process of g-C3N4 and obtained a new photocatalyst (name H-CN) with a higher absorption range, larger specific surface area, and faster hydrogen production activity. Compared with the originally prepared g-C3N4, the H-CN absorption range has been improved, and the utilization of visible light has reached 650 nm. When the doping amount of Pt cocatalyst was 1.0 wt%, the H-CN demonstrates excellent photocatalytic hydrogen production activity, with a hydrogen production rate of 4.3 mmol h−1·g−1, which was 7.0 times higher than that pure 1.0 wt% Pt/g-C3N4. The fluorescence spectroscopy of H-CN showed better separation of carriers and longer lifetime. This study has guiding significance for the preparation of subsequent ultra-thin nanosheet photocatalysts and the establishment of high-efficiency photocatalytic systems.
Porous CuO hollow architectures with perfect octahedral morphology are synthesized simply by annealing Cu-based metal-organic framework (MOF) templates. When tested as anode materials for lithium-ion ...batteries, these hollow octahedra exhibit greatly enhanced performance of lithium storage with excellent cycling stability and good rate capability.
The Boltzmann distribution of electrons sets a fundamental barrier to lowering energy consumption in metal-oxide-semiconductor field-effect transistors (MOSFETs). Negative capacitance FET (NC-FET), ...as an emerging FET architecture, is promising to overcome this thermionic limit and build ultra-low-power consuming electronics. Here, we demonstrate steep-slope NC-FETs based on two-dimensional molybdenum disulfide and CuInP
S
(CIPS) van der Waals (vdW) heterostructure. The vdW NC-FET provides an average subthreshold swing (SS) less than the Boltzmann's limit for over seven decades of drain current, with a minimum SS of 28 mV dec
. Negligible hysteresis is achieved in NC-FETs with the thickness of CIPS less than 20 nm. A voltage gain of 24 is measured for vdW NC-FET logic inverter. Flexible vdW NC-FET is further demonstrated with sub-60 mV dec
switching characteristics under the bending radius down to 3.8 mm. These results demonstrate the great potential of vdW NC-FET for ultra-low-power and flexible applications.
The perovskite solar cell has emerged rapidly in the field of photovoltaics as it combines the merits of low cost, high efficiency, and excellent mechanical flexibility for versatile applications. ...However, there are significant concerns regarding its operational stability and mechanical robustness. Most of the previously reported approaches to address these concerns entail separate engineering of perovskite and charge-transporting layers. Herein we present a holistic design of perovskite and charge-transporting layers by synthesizing an interpenetrating perovskite/electron-transporting-layer interface. This interface is reaction-formed between a tin dioxide layer containing excess organic halide and a perovskite layer containing excess lead halide. Perovskite solar cells with such interfaces deliver efficiencies up to 22.2% and 20.1% for rigid and flexible versions, respectively. Long-term (1000 h) operational stability is demonstrated and the flexible devices show high endurance against mechanical-bending (2500 cycles) fatigue. Mechanistic insights into the relationship between the interpenetrating interface structure and performance enhancement are provided based on comprehensive, advanced, microscopic characterizations. This study highlights interface integrity as an important factor for designing efficient, operationally-stable, and mechanically-robust solar cells.
The development of portable and wearable electronics has promoted increasing demand for high-performance power sources with high energy/power density, low cost, lightweight, as well as ultrathin and ...flexible features. Here, a new type of flexible Ni/Fe cell is designed and fabricated by employing Ni(OH)2 nanosheets and porous Fe2O3 nanorods grown on lightweight graphene foam (GF)/carbon nanotubes (CNTs) hybrid films as electrodes. The assembled f-Ni/Fe cells are able to deliver high energy/power densities (100.7 Wh/kg at 287 W/kg and 70.9 Wh/kg at 1.4 kW/kg, based on the total mass of active materials) and outstanding cycling stabilities (retention 89.1% after 1000 charge/discharge cycles). Benefiting from the use of ultralight and thin GF/CNTs hybrid films as current collectors, our f-Ni/Fe cell can exhibit a volumetric energy density of 16.6 Wh/l (based on the total volume of full cell), which is comparable to that of thin film battery and better than that of typical commercial supercapacitors. Moreover, the f-Ni/Fe cells can retain the electrochemical performance with repeated bendings. These features endow our f-Ni/Fe cells a highly promising candidate for next generation flexible energy storage systems.
Vacancy engineering, that is, self-doping of vacancy in semiconductors, has become a commonly used strategy to tune the photocatalytic performances. However, there still lacks fundamental ...understanding of the role of the vacancies in semiconductor materials. Herein, the g-C3N4 nanosheets with tunable nitrogen vacancies are prepared as the photocatalysts for H2 evolution and CO2 reduction to CO. On the basis of both experimental investigation and DFT calculations, nitrogen vacancies in g-C3N4 induce the formation of midgap states under the conduction band edge. The position of midgap states becomes deeper with the increasing of nitrogen vacancies. The g-C3N4 nanosheets with the optimized density of nitrogen vacancies display about 18 times and 4 times enhancement for H2 evolution and of CO2 reduction to CO, respectively, as compared to the bulk g-C3N4. This is attributed to the synergistic effects of several factors including (1) nitrogen vacancies cause the excitation of electrons to midgap states below the conduction band edge, which results in extension of the visible light absorption to photons of longer wavelengths (up to 598 nm); (2) the suitable midgap states could trap photogenerated electrons to minimize the recombination loss of photogenerated electron–hole pairs; and (3) nitrogen vacancies lead to uniformly anchored small Pt nanoparticles (1–2 nm) on g-C3N4, and facilitate the electron transfer to Pt. However, the overintroduction of nitrogen vacancies generates deeper midgap states as the recombination centers, which results in deterioration of photocatalytic activities. Our work is expected to provide new insights for fabrication of nanomaterials with suitable vacancies for solar fuel generation.
Nano-sized high entropy alloy (HEA) catalysts have attracted much attention as extraordinary electrocatalysts in water-splitting applications,
i.e.
, the hydrogen evolution reaction (HER) and oxygen ...evolution reaction (OER). Recently, there has been heightened interest in metal-free HEA catalysts, which are often considered more sustainable than their noble metal counterparts, while still performing competitively. Therefore, updating the current progress of the state-of-the-art electrolysis of HEAs is essential. This review aims to summarize the recent research progress of noble metal-free HEA nanocatalysts and their performances in the HER and OER. The critical concepts of HEAs, recently reported preparation methods and their performances in water-splitting are focused on in this review. This review also provides a perspective on the existing limitations of HEAs and an outlook for research into noble metal-free HEA nanocatalysts for the HER and OER.
Nano-sized high entropy alloy (HEA) catalysts have attracted much attention as extraordinary electrocatalysts in water-splitting applications,
i.e.
, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
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