Nickel-Modified Biocarbons from Mixed Wood Sawdust: Multitechnique Study of Structure and Photocatalytic Activity

The increasing environmental pollution with persistent organic compounds demands the development of sustainable materials capable, among others, of simultaneous adsorption and catalytic degradation of pollutants. In this study, nickel-modified biocarbons were obtained in the process of biomass pyrolysis at the temperatures of 500 and 800 °C, with the Ni content of 5 and 10% by weight, in order to determine the effect of synthesis conditions on the structure, surface chemistry and functional properties of materials. A wide range of research methods was used to analyze structural parameters, elemental composition, surface morphology, functional groups as well as adsorption and photocatalytic properties. The results indicate that the pyrolysis temperature is the main factor determining the evolution of biocarbons, leading to a decrease in the specific surface area and microporosity, an increase in carbon aromatization, a reduction in oxygen groups, and an increase in alkalinity and thermal stability. The addition of nickel promotes formation of crystalline Ni phases and redox centers, while partially blocking micropores. As a result, the materials obtained at 800 °C are characterized by an increased photocatalytic activity. The paper provides mechanistic insights into the structure-property-function relationships and practical guidance for the design of biocarbons with optimized adsorption and photocatalytic properties.