Solution-Processed CoFe₂O₄ Nanoparticles on 3D Carbon Fiber Papers for Durable Oxygen Evolution Reaction

We report CoFe₂O₄ nanoparticles (NPs) synthesized using a facile hydrothermal growth and their attachment on 3D carbon fiber papers (CFPs) for efficient and durable oxygen evolution reaction (OER). The CFPs covered with CoFe₂O₄ NPs show orders of magnitude higher OER performance than bare CFP due to high activity of CoFe₂O₄ NPs, leading to a small overpotential of 378 mV to get a current density of 10 mA/cm². Significantly, the CoFe₂O₄ NPs-on-CFP electrodes exhibit remarkably long stability evaluated by continuous cycling (over 15 h) and operation with a high current density at a fixed potential (over 40 h) without any morphological change and with preservation of all materials within the electrode. Furthermore, the CoFe₂O₄ NPs-on-CFP electrodes also exhibit hydrogen evolution reaction (HER) performance, which is considerably higher than that of bare CFP, acting as a bifunctional electrocatalyst. The achieved results show promising potential for efficient, cost-effective, and durable hydrogen generation at large scales using earth-abundant materials and cheap fabrication processes

Solution-Processed CoFe₂O₄ Nanoparticles on 3D Carbon Fiber Papers for Durable Oxygen Evolution Reaction

We report CoFe₂O₄ nanoparticles (NPs) synthesized using a facile hydrothermal growth and their attachment on 3D carbon fiber papers (CFPs) for efficient and durable oxygen evolution reaction (OER). The CFPs covered with CoFe₂O₄ NPs show orders of magnitude higher OER performance than bare CFP due to high activity of CoFe₂O₄ NPs, leading to a small overpotential of 378 mV to get a current density of 10 mA/cm². Significantly, the CoFe₂O₄ NPs-on-CFP electrodes exhibit remarkably long stability evaluated by continuous cycling (over 15 h) and operation with a high current density at a fixed potential (over 40 h) without any morphological change and with preservation of all materials within the electrode. Furthermore, the CoFe₂O₄ NPs-on-CFP electrodes also exhibit hydrogen evolution reaction (HER) performance, which is considerably higher than that of bare CFP, acting as a bifunctional electrocatalyst. The achieved results show promising potential for efficient, cost-effective, and durable hydrogen generation at large scales using earth-abundant materials and cheap fabrication processes

Taper PbZr_0.2Ti_0.8O₃ Nanowire Arrays: From Controlled Growth by Pulsed Laser Deposition to Piezopotential Measurements

Single crystalline PbZr_0.2Ti_0.8 (PZT) nanowires arrays (NWAs) with taper morphology were epitaxially grown on SrTiO₃ (STO) substrate using pulse laser deposition. The taper morphology was attributed to the overcoating of PZT layer <i>via</i> a lateral growth of PZT clusters/adatoms during PZT NW growth. The growth window for PZT film or nanowire was systematically studied at varied temperatures and pressures. The proposed growth mechanism of the taper PZT NWAs was investigated from a layer by layer growth <i>via</i> Frank–Van Der Merwe growth, followed by a formation of three-dimensional islands <i>via</i> Stranski–Krastanow growth, and then axial growth on the lowest energy (001) plane with growth direction of [001] <i>via</i> vapor–solid growth mechanism. However, under certain conditions such as at higher or lower pressure (>400 or <200 mTorr) or substrate temperatures (>850 °C and <725 °C), formation of the PZT NWs is suppressed while the epitaxial PZT thin film <i>via</i> the layer-by-layer growth remains. The controllable growth directions of the PZT NWAs on (001), (110), and (111) STO substrates were demonstrated. The piezopotential of the taper PZT NWAs using a conducting atomic force microscope with the average voltage output of ∼18 mV was measured. The theoretical piezopotential of a PZT NW was calculated to compare with the measured outputs, providing a comprehensively experimental and theoretical understanding of the piezoelectricity for the PZT NW

Nanoscale InGaSb Heterostructure Membranes on Si Substrates for High Hole Mobility Transistors

As of yet, III–V p-type field-effect transistors (p-FETs) on Si have not been reported, due partly to materials and processing challenges, presenting an important bottleneck in the development of complementary III–V electronics. Here, we report the first high-mobility III–V p-FET on Si, enabled by the epitaxial layer transfer of InGaSb heterostructures with nanoscale thicknesses. Importantly, the use of ultrathin (thickness, ∼2.5 nm) InAs cladding layers results in drastic performance enhancements arising from (i) surface passivation of the InGaSb channel, (ii) mobility enhancement due to the confinement of holes in InGaSb, and (iii) low-resistance, dopant-free contacts due to the type III band alignment of the heterojunction. The fabricated p-FETs display a peak effective mobility of ∼820 cm²/(V s) for holes with a subthreshold swing of ∼130 mV/decade. The results present an important advance in the field of III–V electronics