ZnxCo3‐xO4 nanoarrays are grown hydrothermally on Ti foils using appropriate ratios of Zn(NO3)2 and Co(NO3)2, NH4F and Co(NH2)2 in H2O together with the Ti substrate (autoclave, 120 °C, 10 h).
β-Ni(OH)(2) was constructed into a three-dimensional mesoporous film on Ni foam with ultra-thin (∼6 nm) primary nanowalls showing ultrahigh specific capacitance (2675 F g(-1)) and excellent cycling performance (>96% for 500 cycles). The capacitance was higher than theoretical value possibly due to the combination of Faradic and electrical double-layer capacitances.
Direct liquid-feed fuel cells possess high energy and power densities, but suffer from severe adhesion of gas products. Here, a "superaerophobic" surface that enables a small release size and fast evolution behavior of the gas product is introduced, thereby, maximizing and stabilizing the working area. Consequently, the "superaerophobic" nanostructured Cu electrodes exhibit excellent performance as anodes in a direct hydrazine fuel cell.
Hydrogen evolution reaction (HER) has prospect to becoming clean and renewable technology for hydrogen production and Ni-Mo alloy is among the best HER catalysts in alkaline electrolytes. Here, an in situ topotactic reduction method to synthesize ultrathin 2D Ni-Mo alloy nanosheets for electrocatalytic hydrogen evolution is reported. Due to its ultrathin structure and tailored composition, the as-synthesized Ni-Mo alloy shows an overpotential of 35 mV to reach a current density of 10 mA cm , along with a Tafel slope of 45 mV decade , demonstrating a comparable intrinsic activity to state-of-art commercial Pt/C catalyst. Besides, the vertically aligned assemble structure of the 2D NiMo nanosheets on conductive substrate makes the electrode "superaerophobic," thus leading to much faster bubble releasing during HER process and therefore shows faster mass transfer behavior at high current density as compared with drop drying Pt/C catalyst on the same substrate. Such in situ topotactic conversion finds a way to design and fabricate low-cost, earth-abundant non-noble metal based ultrathin 2D nanostructures for electrocatalytic issues.
Previously reported examples of electrochemical pseudocapacitors based on cheap metal oxides have suffered from the need to compromise between specific capacitance, rate capacitance, and reversibility. Here we show that NiO nanorod arrays on Ni foam have a combination of ultrahigh specific capacitance (2018 F/g at 2.27 A/g), high power density (1536 F/g at 22.7 A/g), and good cycling stability (only 8% of capacitance was lost in the first 100 cycles with no further change in the subsequent 400 cycles). This resulted in an improvement in the reversible capacitance record for NiO by 50% or more, reaching 80% of the theoretical value, and demonstrated that a three-dimensional regular porous array structure can afford all of these virtues in a supercapacitor. The excellent performance can be attributed to the slim (< 20 nm) rod morphology, high crystallinity, regularly aligned array structure and strong bonding of the nanorods to the metallic Ni substrate, as revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).
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