Solution-processed Cu2−xO-Fe2O3 composites as novel supercapacitor anodic materials

Corrosion Resistance of Fe-Based Amorphous Films Prepared by the Radio Frequency Magnetron Sputter Method

Amorphous thin films can be applied to increase the anti-corrosion ability of critical components. Atomized FeCrNiMoCSiB powders were hot-pressed into a disc target for R. F. magnetron sputtering on a 316L substrate to upgrade its corrosion resistance. The XRD spectrum confirmed that the film deposited by R. F. magnetron sputtering was amorphous. The corrosion resistance of the amorphous film was evaluated in a 1 M HCl solution with potentiodynamic polarization tests, and the results were contrasted with those of a high-velocity oxy-fuel (HVOF) coating and 316L, IN 600, and C 276 alloys. The results indicated that the film hardness and elastic modulus, as measured using a nanoindenter, were 11.1 and 182 GPa, respectively. The principal stresses in two normal directions of the amorphous film were about 60 MPa and in tension. The corrosion resistance of the amorphous film was much greater than that of the other samples, which showed a broad passivation region, even in a 1 M HCl solution. Although the amorphous film showed high corrosion resistance, the original pinholes in the film were weak sites to initiate corrosion pits. After polarization tests, large, deep trenches were seen in the corroded 316L substrate; numerous fine patches in the IN 600 alloy and grain boundary corrosion in the C276 alloy were observed.

Electrochemically Triggered Self-Adaptive Reconstruction of an all-Purpose Electrode for Photothermally Enhanced Capacitors

Large-capacity energy storage devices are attracting widespread research attention. However, the decreased capacity of these devices due to cold weather is a huge obstacle for their practical use. In this study, an electrochemical self-adaptive reconstructed Cux S/Cu(OH)2 -based symmetric energy storage device is proposed. This device provides a satisfactorily enhanced photothermal capacity under solar irradiation. After electrochemical reconstruction treatment, the morphological structure is rearranged and the Cux S component is partially converted to electrochemically active Cu(OH)2 with the introduction of a large number of active sites. The resulting Cux S/Cu(OH)2 electrode provides a significant capacitance of 115.2 F cm-2 at 5 mA cm-2 . More importantly, its wide working potential range and superior photo-to-thermal conversion ability endow Cux S/Cu(OH)2 with superb performance as full-purpose photothermally enhanced capacitance electrodes. Under solar irradiation, the surface temperature of Cux S/Cu(OH)2 is elevated by 76.6 °C in only 30 s, and the capacitance is boosted to 230.4% of the original capacitance at a low temperature. Furthermore, the assembled symmetric energy storage device also delivers a photothermal capacitance enhancement of 200.3% under 15 min solar irradiation.

3D Porous Compact 1D/2D Fe2 O3 /MXene Composite Aerogel Film Electrodes for All-Solid-State Supercapacitors

2D MXene nanoflakes usually undergo serious restacking, that easily aggravates during the traditional vacuum-assisted filtration process; and thus, hinders the electrochemical performance of the corresponding film electrodes. Herein, 3D porous compact 1D/2D Fe₂ O₃ /MXene aerogel film electrode with an enhanced electrochemical performance is fabricated by freeze-drying assisted mechanical pressing. An introduction of 1D α-Fe₂ O₃ nanorods can not only alleviate the restacking of 2D MXene but also provide additional pseudocapacitance for the composite film system. Thus, the resulting Fe₂ O₃ /MXene aerogel film electrode shows an enhanced specific capacitance of 182 F g^-1 (691 mF cm^-2 ) at a current density of 1 A g^-1 in 3 m H₂ SO₄ electrolyte as well as with 81.74% capacitance retention after 10 000 charge-discharge cycles. Besides, the addition of 1D α-Fe₂ O₃ nanorods has a significant contribution in the volumetric capacitance of the composite aerogel film (150 F cm^-3 ), which is 2.68 times that of the pure MXene aerogel film (56 F cm^-3 ). Moreover, the fabricated all-solid-state symmetric supercapacitor (SSSC) delivers a superior areal energy density of 3.61 µWh cm^-2 at a power density of 119.04 µW cm^-2 . This rapid-forming 3D porous, binder-free, and freestanding aerogel film provides a progressive strategy for the fabrication of MXene-based electrode for supercapacitors.

Three-Dimensional Self-Supporting Ti3C2 with MoS2 and Cu2O Nanocrystals for High-Performance Flexible Supercapacitors

The three-dimensional (3D) architecture of electrode materials with excellent stability and electrochemical activity is extremely desirable for high-performance supercapacitors. In this study, we develop a facile method for fabricating 3D self-supporting Ti₃C₂ with MoS₂ and Cu₂O nanocrystal composites for supercapacitor applications. MoS₂ was incorporated in Ti₃C₂ using a hydrothermal method, and Cu₂O was embedded in two-dimensional nanosheets by in situ chemical reduction. The resulting composite electrode showed a synergistic effect between the components. Ti₃C₂ served as a conductive additive to connect MoS₂ nanosheets and facilitate charge transfer. MoS₂ acted as an active spacer to increase the interlayer space of Ti₃C₂ and protect Ti₃C₂ from oxidation. Cu₂O effectively prevented the collapse of the lamellar structure of Ti₃C₂-MoS₂. Consequently, the optimized composite exhibited an excellent specific capacitance of 1459 F g^-1 at a current density of 1 A g^-1. Further, by assembling an all-solid-state flexible supercapacitor with activated carbon, a high energy density of 60.5 W h kg^-1 was achieved at a power density of 10³ W kg^-1. Additionally, the supercapacitor exhibited a capacitance retention of 90% during 3000 charging-discharging cycles. Moreover, high mechanical robustness was retained after bending at different angles, thereby suggesting significant potential applications for future flexible and wearable devices.

Cu-MOF derived Cu-C nanocomposites towards high performance electrochemical supercapacitors

For the development of asymmetric supercapacitors with higher energy density, the study of new electrode materials with high capacitance is a priority. Herein, the electrochemical behavior of nano copper in alkaline electrolyte is first discovered. It is found that there are two obvious reversible redox symmetric peaks in the range of -0.8-0.2 V in the alkaline electrolyte, corresponding to the conversion of copper into cuprous ions, and then converting cuprous ions into copper ions, indicating that the nanocomposite electrode has the characteristics of a pseudocapacitive reaction. It has a specific capacitance of up to 318 F g-1 at a current density of 1 A g-1, which remains at nearly 100% after 10 000 cycles at the same current density. When assembled with a Ni(OH)2-based electrode into an asymmetric supercapacitor, the device shows excellent capacitive behavior and good reaction reversibility. At 0.4 A g-1, the supercapacitor delivers a reversible capacity of 8.33 F g-1 with an energy density of 13.5 mW h g-1. This study first discovers the electrochemical behavior of nano copper, which can provide a new research idea for further expanding the negative electrodes of supercapacitors with higher energy density.