Hybrid electrodes exhibit intriguing properties due to the synergetic effect of different components that are propitious for the practical applications of thermo-cells (TECs). In this study, Ag–carbon nanotube (CNT) hybrid electrodes were prepared using two simple and effective steps, involving the direct growth of CNTs on stainless steel substrates without any external catalyst, followed by decorating the CNTs with Ag nanoparticles. Ag–CNT electrodes were characterized via scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy and were applied in TECs for the first time. The TEC performances of the Ag–CNT electrodes were significantly enhanced compared to that of the pristine CNT electrode due to their better conductivity and thermal conductivity, as well as more activation sites. The results show that the construction of Ag–CNT hybrid electrodes can effectively improve the TEC performances of CNT electrodes, which is promising for heat energy harvesting by CNT-based electrodes.

Ag–ZnO nanocomposites were prepared on alloy substrates by two simple and inexpensive steps, i.e. synthesis of ZnO nanorod arrays (ZNAs) by a low-temperature hydrothermal method, followed by electrophoretic deposition method to coat ZNAs with Ag nanoparticles (NPs). The sizes and densities of the Ag NPs could be facilely adjusted by changing the deposition time. The field emission (FE) performances of Ag–ZnO emitters were improved greatly by adjusting the sizes and densities of the Ag NPs, and the optimized FE performance of the Ag–ZnO emitter was obtained with the lowest turn-on field of 0.86 V μm⁻¹ and a current density up to 7.96 mA cm⁻² at 4.45 V μm⁻¹. More importantly, the Ag–ZnO emitter exhibited excellent current stabilities with 1900 min operation under only 6.5% current fluctuation. These results suggest that the Ag–ZnO composite is a promising cathode material for fabrication of future FE devices.

The application of carbon nanotubes (CNTs) as a thermo-electrochemical cell (TEC) electrode is still difficult due to their weak contact with the substrate during the electrophoretic deposition (EPD) method. In this study, by doping the suspension of the CNTs with Mg²⁺ and Ag powder, Ag–MgO–CNT nanocomposites were successfully prepared on a stainless steel (SS) substrate using the EPD method. The products were confirmed using characterization by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray and X-ray photoelectron spectroscopy. The TEC performance of the Ag–MgO–CNTs nanocomposite electrodes was significantly improved due to their higher conductivity, thermal conductivity and improved adhesion between the composite film and the SS substrate, depending on the concentrations of the Ag powder. The results suggest that constructing Ag–MgO–CNTs nanocomposite electrodes can effectively enhance the performance of CNTs-based TECs, which might be a promising way for energy harvesting using CNTs-based TECs prepared via the EPD technique.

MnO₂–MWNT–Ni foam supercapacitor electrodes were developed based on directly grown multiwalled carbon nanotubes (MWNTs) and hydrothermal MnO₂ nanostructures on Ni foam substrates. The electrodes demonstrated excellent electrochemical and battery properties. The charge transfer resistance dropped 88.8% compared with the electrode without MWNTs. A high specific capacitance of 1350.42 F·g⁻¹ was reached at the current density of 6.5 A·g⁻¹. The electrode exhibited a superior rate capability with 92.5% retention in 25,000 cycles. Direct MWNT growth benefits the supercapacitor application for low charge transfer resistance and strong MWNT–current collector binding.

Carbon nanotube-Graphene (CNT-Gr) hybrids were prepared on stainless steel substrates by the electrophoretic deposition (EPD) to make the thermo-electrochemical cell (TEC) electrodes. The as-obtained TEC electrodes were investigated by the SEM, XRD, Raman spectroscopy, tensile, and surface resistance tests. These hybrid electrodes exhibited significant improved TEC performances compared to the pristine CNT electrode. In addition, these hybrid electrodes could be optimized by tuning the contents of the graphene in the hybrids, and the CNT-Gr-0.1 hybrid electrode showed the best TEC performance with the current density of 62.8 A·m⁻² and the power density of 1.15 W·m⁻², 30.4% higher than the CNT electrode. The enhanced TEC performance is attributed to improvements in the electrical and thermal conductivities, as well as the adhesion between the CNT-Gr hybrid and the substrate. Meanwhile, the relative conversion efficiency of the TECs can reach 1.35%. The investigation suggests that the growth of CNT-Gr hybrid electrodes by the EPD technique may offer a promising approach for practical applications of the carbon nanomaterial-based TEC electrodes.

Nitrogen doped carbon nanotube arrays (NCNTA) were synthesized by a catalyst-free chemical vapor deposition (CVD) method using ZnO nanorod arrays as a template. The as-prepared NCNT samples, with open-ended morphologies, were characterized by SEM, Raman, TEM, EDS, and XPS analysis. The field emission (FE) properties of the NCNT emitters were investigated and optimized by improving the deposition time of pyridine with a low turn-on field of 0.36 V μm⁻¹ and a high field enhancement factor of 65 199, which are superior to those of CNTs prepared using an anodic alumina oxide template. First-principles calculations indicate that the improved FE performance of the NCNT is attributed highly to the decrease of the work function. In addition, in comparison with the NCNT prepared by the catalyst-support CVD method, the enhancement of the FE performance of the NCNT is mainly due to the higher field enhancement factor. Meanwhile, the current fluctuation of the NCNT sample is about 2.3% at 1.36 mA cm⁻² after 1200 min continuous operation under a pressure of 4.5 × 10⁻⁵ Pa. These results suggest that the NCNT emitter based on the ZnO nanotemplate is promising to develop FE devices.