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Electrochemical deposition of cobalt nanoparticles was used to modify carrier transport properties of single-layered CVD graphene at the SiO₂-on-Si substrate. The structure of graphene with cobalt nanoparticles was analyzed by Raman spectroscopy and scanning electron microscopy. The effect of the deposited cobalt nanoparticles on the sheet resistance of graphene was studied in the temperature range of 4–300K.

Co doped mesoporous carbon composites (MC–Co) have been synthesized at different carbonization temperatures via evaporation-induced multicomponent co-assembly strategy. The nanostructures and chemical compositions of MC–Co composites were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction analysis (XRD), etc. Their electromagnetic and microwave absorption properties were investigated in the frequency ranging from 2 GHz to 18 GHz. By the measurement of electromagnetic parameters and theoretical simulation of reflection loss (RL), the results showed that the minimum RL value of the optimum composite MC–Co-800 reached up to -41.9 dB at 13.5 GHz with a thickness of only 1.80 mm, and the effective absorption bandwidth (< -10 dB) is 4.4 GHz (from 11.4 GHz to 15.8 GHz). This work demonstrated that the optimum carbonization temperature of the obtained composites is 800°C, which is critical to its electromagnetic properties. The excellent microwave absorption properties can be attributed to dielectric loss, Ohmic loss, and characteristic impedance matching. Therefore, the as-synthesized composites could be acted as a candidate of microwave absorber, especially for the light weight demand.

$M$–N_x–C ($M$=Fe, Co, etc.) substances received tremendous attention due to its outstanding performance for oxygen reduction reaction and oxygen evolution reaction. Usually, metal nanoparticles could form simultaneously during synthesis process, whereas these nanoparticles received very little attention since they were often removed by acid etching. Here, we designed and synthesized an active-N-dominated Co, N co-doped carbon layers supported Co nanoparticles material (denoted as CoNPs@CoNC) by annealing the composites of Co-Phen confined in porous carbon supports together with urea at 900^∘C. Compared with the acid etching CoNC catalyst without the surface Co nanoparticles, CoNPs@CoNC catalyst exhibited a higher Co content and slightly positive shifting of the main peak of Co 2p3/2 that is closely associated with the tuned electronic structure. Additionally, the as-prepared CoNPs@CoNC catalyst provided a superior performance ($E_{j=1∕2}=0.86$V versus RHE, ${\eta }_{j=10}=0.36$V) than that of CoNC catalyst ($E_{j=1∕2}=0.81$V, ${\eta }_{j=10}=0.44$V), which led to a lower reversible overvoltage of 0.73V for CoNPs@CoNC. Furthermore, the superior performance enabled the CoNPs@CoNC-based Zn–air battery catalyst with a more admirable charge-discharge performance in terms of open-circuit voltage, energy density and power density, unveiling its immense potential in realistic utilization.

4-nitrophenol (4-NP) is a highly toxic pollutant for aquatic ecosystem and human life. Therefore, the catalytic reduction of 4-NP into useful 4-aminophenol (4-AP) is of interest. In this regard, two heterogeneous nanocatalysts, including Ag@HNTs-ILs and Co@HNTs-ILs were prepared by grafting imidazolium-based ionic liquids (ILs) onto the halloysite nanotubes (HNTs), followed by immobilization of Ag and Co nanoparticles (NPs), and characterized by means of FT-IR, SEM, EDX, TEM and XRD. The catalytic activity of the prepared nanocatalysts was evaluated for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) under environmentally friendly condition. A set of time, temperature, nanocatalyst amount and NaBH₄/4-NP molar ratios was screened. The reusability experiments demonstrated that Ag@HNTs-ILs and Co@HNTs-ILs were highly reusable, up to five reduction cycles without considerable changes in the reaction time. As the synthesized hybrid nanocatalysts could be re-collected and reused for various catalytic runs without any significant loss in their catalytic activity, they could be considered very promising nanomaterials from sustainability point of view.

Developing advanced catalysts with high activity and low cost is a hot topic for CO₂ methanation at low temperatures. Co/C catalysts with well-dispersed Co nanoparticles in the channels of the ordered mesoporous carbons have been synthesized with high specific surface area and uniform pore size. Then, size control and Ru incorporation have been conducted to promote the catalytic activity. The results show that Ru–Co/C catalysts with smaller particle size ($\sim 3$nm) and mono-dispersion achieve CO₂ conversion rate of 31.7% and CH₄ selectivity up to 75.8%. Importantly, Ru–Co/C catalysts yield 29.9% CO₂ conversion and space-time yield (CH₄) of 44.5 (mmol/gcat$\cdot$min) even at 5 bar. It demonstrates the important prospect of structured carbon-supported metal catalysts for low-temperature and low-pressure CO₂ methanation.