Agricultural waste derived silicon carbide composite nanopowders as efficient coelectrocatalysts for water splitting

Various silicon carbide nanostructures are attracting close attention due to their excellent performance and great potential, including utilization in a variety of catalytic applications. Approaches, utilizing different industrial wastes as a starting material for the synthesis of SiC nanoparticles, are especially distinguished due to their environmental friendliness. This paper demonstrates a new two-stage technique of the preparation of dispersed SiC/C nanocomposite. A highly mineralized carbonaceous residue obtained by thermal processing of agricultural waste was used as a precursor for the synthesis in a pulsed arc discharge plasma. Rice husks, oat husks and oat straw were chosen as agricultural wastes with a high content of silicon in the mineral component. Carbonaceous residues (biochars) were obtained from the selected wastes by oxidative carbonization in a reactor with a fluidized bed of a deep oxidation catalyst at 460 °C. High-energy (up to 20 kJ) treatment of the obtained biochars in a pulsed (up to 1 ms) arc discharge plasma jet resulted in synthesizing a nanodispersed material (particle size <50 nm) containing hexagonal silicon carbide α-SiC. The principal possibility of using the synthesized SiC-based composite as a catalyst and cocatalyst of platinum in the hydrogen evolution reaction (HER) of water splitting is shown. The most impressive results (η10 = 18–28 mV, η100 = 84–98 mV, b = 32–64 mV) comparable with standard commercial Pt/C samples were obtained by modifying the synthesized SiC-based composite with 5 % platinum. Thus, the developed approach allows us to convert the agricultural waste into useful high-tech products in the form of an electrocatalytically active material.