Lotus-biowaste derived sulfur/nitrogen-codoped porous carbon as an eco-friendly electrocatalyst for clean energy harvesting

Recent research is focused on biomass-derived porous carbon materials for energy harvesting (hydrogen evolution reaction) because of their cost-effective synthesis, enriched with heteroatoms, lightweight, and stable properties. Here, the synthesis of porous carbon (PC) materials from lotus seedpod (LP) and lotus stem (LS) is reported by the pyrolysis method. The porous and graphitic structure of the prepared LP-PC and LS-PC materials were confirmed by field emission scanning electron microscopy, transmission electron microscopy with selected area electron diffraction, X-ray diffraction, and nitrogen adsorption-desorption measurements. Heteroatoms in LP-PC and LS-PC materials were investigated by attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy. The specific surface area of LP-PC and LS-PC were calculated as 457 and 313 m2 g-1, respectively. Nitrogen and sulfur enriched LP-PC and LS-PC materials were found to be effective electrocatalysts for hydrogen evolution reactions. LP-PC catalyst showed a very low overpotential of 111 mV with the Tafel slope of 69 mV dec-1, and LS-PC catalyst achieved a Tafel slope of 85 mV dec-1 with a low overpotential of 135 mV. This work is expected to be extended for the development of biomass as a sustainable porous carbon electrocatalyst with a tunable structure, elements, and electronic properties. Furthermore, preparing carbon materials from the biowaste and applying clean energy harvesting might reduce environmental pollution.