Ance Plavniece

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs.

Biomass valorization into carbon-rich materials has attracted increasing attention as a sustainable alternative to fossil-based resources. This work is devoted to the study of hydrothermal carbonization (HTC) of spruce lignocellulose liquid pyrolysis products (the target product of the pyrolysis is levoglucosan)—bio-oil (B). In addition, the fractionated B compounds, including the phenol-enriched fraction remaining after anhydrosugar removal, were evaluated as potential precursors for hydrochar production. Hydrochars were produced at 200, 250, and 300 °C and characterized using SEM, revealing that spherical morphology agglomerates can also be obtained from the phenol-enriched fraction. The chemical composition and structural evolution of the hydrochars were investigated by Py-GC/MS, elemental analysis, and FTIR, demonstrating the significant influence of both precursor composition and carbonization temperature on hydrochar chemistry. In addition, the organic compounds in the process water were analyzed using UHPLC and complementary chemical analysis. The results show that the chemical composition of the precursor strongly influences the yield, morphology, and chemical composition of the obtained hydrochar.

In this study the development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) was synthesized using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim to create efficient materials for hydrazine oxidation (HzOR) and direct hydrazine-hydrogen peroxide fuel cells (DHHPFC, N2H4–H2O2). The composition, structure, and surface morphology of the created catalysts were examined using inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N2H4–H2O2 fuel cell tests were carried out by employing the catalysts both as the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm–2), outperforming AWC–Cu–N (17.7 mW cm–2). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs.

The decline of fossil fuel resources and the negative impact of fuel combustion on the environment are forcing scientists to develop new technologies for producing functional carbon materials with various useful properties. This work is devoted to a detailed study of the transformations of monosaccharides, glucose and levoglucosan, during hydrothermal carbonization, aimed at the formation of carbon microspheres. Hydrochars were obtained at temperatures of 200, 250, and 300 °C and characterized using SEM, Py-GC/MS, and elemental analysis. Changes in the chemical composition of the liquid phase were studied, depending on the HTC temperature and precursor concentration. Expanded knowledge of microsphere formation enriches information on the mechanism of monosaccharide transformation for the production of new carbon materials through synthesis from inexpensive precursors.

This study presents a straightforward strategy for producing novel, effective and inexpensive functional non-noble metal-supported carbon materials made from abundant natural biomass. These materials offer a cost-effective alternative to noble metals for the oxidation of hydrazine (HzOR) and demonstrate the potential for widespread adoption of green, energy-saving hydrazine-based technologies in energy applications. Highly efficient and cost-effective iron (Fe) and manganese–iron (MnFe)-supported nitrogen-doped carbon (N–C) materials were developed using hydrothermal synthesis. Meanwhile, the N–C material was obtained from biomass—birch-wood chips—using hydrothermal carbonisation (HTC), followed by activation and nitrogen doping of the resulting hydrochar. The morphology, structure, and composition of the MnFe, MnFe/N–C, and Fe/N–C catalysts were determined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDS). The activity of the catalysts for HzOR in an alkaline medium was evaluated using cyclic voltammetry (CV). Depositing MnFe particles onto N–C was shown to significantly enhance electrocatalytic activity for HzOR compared to the Fe/N–C catalyst and especially to the MnFe particles catalyst in terms of highly developed porous structure, which offers the largest surface area, lowest onset potential, and highest current density response, resulting in the strongest catalytic activity. These results suggest that the MnFe/N–C catalyst could be a highly promising anode material for HzOR in direct hydrazine fuel cells (DHFCs).

In this study, a straightforward strategy for the preparation of functional carbon-based materials for hydrazine oxidation (HzOR) is presented. A highly efficient, cost-effective iron (Fe) and manganese-iron (MnFe) supported nitrogen-doped carbon (N-C) material was developed using a hydrothermal synthesis method. Meanwhile, N-C material was obtained from biomass – birch-wood chips – using hydrothermal carbonisation (HTC), followed by the activation and nitrogen doping of the resulting hydrochar. The material has a large specific surface area of 2431 m2 g−1 and a micro-mesoporous structure con-taining over 50% mesopore volume. The morphology, structure, and composition of the MnFe, MnFe/N-C, and Fe/N-C catalysts were determined using scanning electron micros-copy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX). The activity of the catalysts for the HzOR in an alkaline medium was evaluated using cyclic voltammetry (CV). The deposition of MnFe particles on N-C has been shown to result in a significant enhancement of electrocatalytic activity for HzOR in comparison with pure MnFe particles. The hydrazine oxidation current density values, measured at an electrode potential of 1.6 V vs. RHE, were found to be approximately 7 and 9 times higher on the Fe/N-C and MnFe/N-C catalysts, respectively, than on the MnFe catalyst.

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was also synthesized. Extensive characterization, including SEM, Raman spectroscopy, XPS, and XRD revealed the catalysts’ microstructure and properties. Electrochemical testing demonstrated that the AWC-Ni-N catalyst significantly enhanced the efficiency of the hydrazine oxidation reaction. In addition, direct N₂H₄-H₂O₂ single-fuel-cell tests were conducted using the prepared AWC-N and AWC-Ni-N catalysts as the anodes and cathodes. Peak power densities of up to 10.8 mW cm⁻² were achieved at 25 °C, corresponding to a current density of 27 mA cm⁻² and a cell voltage of 0.4 V when the AWC-Ni-N catalyst was used as both the anode and cathode. Furthermore, the peak power density increased by approximately 1.6 and 2.9 times, respectively, when the operating temperature was raised from 25 °C to 55 °C for the AWC-N and AWC-Ni-N catalysts. Overall, the AWC-N and AWC-Ni-N catalysts demonstrated significant potential as anode and cathode materials in direct N₂H₄-H₂O₂ fuel cells.

The N-doped lignin-based carbon material has a promising activity and stability for its application as supercapacitor as well as non-noble metal-based catalysts for fuel cells, metal–air batteries .

In order to explore the possibilities of increasing the hydrophilicity of carbon-based adsorbents, catalysts, or electrode materials in aqueous solutions, the oxidation of wood-based activated biochar using H₂O₂ was investigated. The properties of oxidized activated biochar obtained at different activation temperatures (600, 700, and 800 °C) and H₂O₂ oxidized for 15–180 min were investigated using the characteristics of surface functionality, elemental composition, porous structure, contact angle measurements, FTIR spectroscopy, and immersion calorimetry. It was observed that the optimal oxidation time was different for each sample depending on activation temperature, and the degree of oxidation can be tailored by changing the oxidation time. The course of oxidation depends on the degree of graphitization and functionalization, determined by the activation temperature. It was established that the highest degree of oxidation and increase in wettability is observed for samples with the lowest degree of activation obtained at a temperature of 600 °C.