In this study, carbon-supported MnO₂ nanocomposites have been prepared using the microwave-assisted heating method followed by two different approaches. The MnO₂/C nanocomposite, labeled as sample S1, was prepared directly by the microwave-assisted synthesis of mixed KMnO₄ and carbon powder components. Meanwhile, the other MnO₂/C nanocomposite sample labeled as S2 was prepared indirectly via a two-step procedure that involves the microwave-assisted synthesis of mixed KMnO₄ and MnSO₄ components to generate MnO₂ and subsequent secondary microwave heating of synthesized MnO₂ species coupled with graphite powder. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectroscopy have been used for characterization of MnO₂/C nanocomposites morphology, structure, and composition. The electrochemical performance of nanocomposites has been investigated using cyclic voltammetry and galvanostatic charge/discharge measurements in a 1 M Na₂SO₄ solution. The MnO₂/C nanocomposite, prepared indirectly via a two-step procedure, displays substantially enhanced electrochemical characteristics. The high specific capacitance of 980.7 F g⁻¹ has been achieved from cyclic voltammetry measurements, whereas specific capacitance of 949.3 F g⁻¹ at 1 A g⁻¹ has been obtained from galvanostatic charge/discharge test for sample S2. In addition, the specific capacitance retention was 93% after 100 cycles at 20 A g⁻¹, indicating good electrochemical stability.

In this study, cobalt-nickel (Co-Ni), cobalt-iron (Co-Fe), cobalt-iron-manganese (Co-Fe-Mn), cobalt-iron-molybdenum (Co-Fe-Mo), and cobalt-zinc (Co-Zn) coatings were studied as catalysts towards the evolution of hydrogen (HER) and oxygen (OER). The binary and ternary Co coatings were deposited on a copper surface using the electroless metal plating technique and morpholine borane (MB) as a reducing agent. The as-deposited Co-Ni, Co-Fe, Co-Fe-Mn, Co-Fe-Mo, and Co-Zn coatings produce compact and crack-free layers with typical globular morphology. It was found that the Co-Fe-Mo coating gives the lowest overpotential of 128.0 mV for the HER and the lowest overpotential of 455 mV for the OER to achieve a current density of 10 mA cm⁻². The HER and OER current density values increase 1.4–2.0 times with an increase in temperature from 25 °C to 55 °C using the prepared 3D binary or ternary cobalt coatings for HER and OER. The highest mass electrocatalytic activity of 1.55 mA µg⁻¹ for HER and 2.72 mA µg⁻¹ for OER was achieved on the Co-Fe coating with a metal loading of 28.11 µg cm⁻² at 25 °C.

In this paper, the generation of hydrogen from alkaline sodium borohydride solution by hydrolysis is studied. To obtain catalysts for efficient hydrogen generation, Ni, Mn, Mo, and Co metals were deposited on the Cu surface by the simple electroless metal deposition method using morpholine borane as a reducing agent. Depending on the peculiarities of the deposition of each metal, the coating thickness was ca. 1 μm for all catalysts. The deposited coatings were compact and crack-free, with multilayer characteristics and a cauliflower-like structure. The prepared Ni/Cu, NiMn/Cu, NiMo/Cu, NiCo/Cu, NiCoMn/Cu, NiCoMo/Cu, and NiCoMoMn/Cu catalysts showed an efficient catalytic activity for sodium borohydride hydrolysis reaction. The lowest activation energy of 45.3 kJ mol⁻¹ for sodium borohydride hydrolysis reaction was obtained using the NiCoMoMn/Cu catalyst. The highest hydrogen generation rate of 3.08 mL min⁻¹ was also achieved using this catalyst at 303 K. With a further increase in temperature to 343 K, the hydrogen generation rate catalyzed by the NiCoMoMn/Cu increased 7.7 times and reached 23.57 mL min⁻¹.

Cobalt–boron (Co–B) coatings containing different amounts of boron were electrolessly deposited using morpholine borane as the reducing agent. Diethylenetriamine (dien) was applied to obtain a controllable amount of boron in the coatings. Depending on the concentration of diethylenetriamine in the solution, the deposited coatings contained between 0 and 12 at% of boron. It was shown that diethylenetriamine suppresses the incorporation of boron into Co–B alloys. The same tendency was observed when the solution pH increased. Higher temperatures promote the incorporation of boron into cobalt films. The kinetic data on the electroless deposition process of Co–B alloys under different conditions are presented and discussed. The coatings obtained were characterized by means of XRD, SEM, and AFM methods. Since the use of diethylenetriamine hinders boron incorporation into coatings, pure cobalt films can be obtained.

The utilization of anodized aluminum (Al) components would contribute greatly to combat against dry friction if good tribological properties could be attained. Despite its hardness, the wear rate of anodic coatings presents a major problem in many applications, including automotive, aerospace and high-tech industries. Recently, nanolayers of Ti demonstrated high tribological effectiveness and unusually low dry friction on anodic coatings. However, few researchers focus on the tribological characterization of nanolayers of other elements. In this study, nanolayers of Ti, Zr, Hf, Cu, Cr, Nb and Sn were deposited on anodized 1050 and 6082 alloys by magnetron sputtering and Atomic Layer Deposition. Major attention was devoted to surface roughness and hardness measurements, because of their importance for static friction. The results showed that structural, chemical and other intrinsic properties of nanolayers of Group IVB elements in many cases led to significant friction reduction, when compared to those of Cu, Cr and Hf. Nanolayers of 15 nm to 75 nm thicknesses appeared most effective tribologically, while 180 nm or thicker layers progressively lost their ability to sustain low dynamic friction. Deposition of nanoscale structures could provide advantages for the anodized Al industry in protection against incidental friction and wear.