Fabrication of Mo ₂ C-Loaded Macadamia Nut Shell-Derived Porous Carbon Composites and Their Hydrogen Evolution and Microwave Absorption Performance

In this study, Mo₂C-loaded macadamia nut shell-derived porous carbon composites (denoted MC) were fabricated via a scalable method to explore their dual functionality for the hydrogen evolution reaction (HER) and microwave absorption. Macadamia nut shells, which are a sustainable biomass source, were carbonized and activated to create a porous carbon matrix, which was then impregnated with ammonium molybdate for Mo₂C formation through carbothermal reduction. The impact of carbonization temperature on the structural and electrochemical properties of the composites was systematically studied. Among the various composites synthesized, MC850 exhibited the most favorable balance of conductivity, pore structure, and Mo₂C dispersion, leading to optimal HER performance and microwave absorption properties. Specifically, MC850 demonstrated a low overpotential of 87.2 mV at a current density of 10 mA·cm^-2, superior electrochemical stability, and outstanding microwave absorption performance with a reflection loss (RL) of -40.6 dB at optimal thickness, achieving nearly complete absorption of incident electromagnetic waves and a broad effective absorption bandwidth. These results underscore the synergistic effects of the carbon structure and Mo₂C integration, providing a pathway for the development of efficient electrocatalysts and lightweight electromagnetic absorbers from biomass-derived materials.