Biomass-derived ultrathin carbon-shell coated iron nanoparticles as high-performance tri-functional HER, ORR and Fenton-like catalysts

The development of cost-effective carbon-shell coated metal-based nanocatalysts is currently a highly desirable goal towards the fabrication of more sustainable non-precious nanocatalysts. Herein, we design an easy, cheap, scalable, and eco-friendly carbothermal reduction strategy to develop core-shell structured metallic iron nanoparticles using coffee waste grounds as starting renewable materials (Fe@BMC). The structural properties of the as-synthesized nanoparticles were nicely tuned by varying the reaction temperature. Remarkably, ultrathin carbon-shell coated metallic iron nanoparticles were obtained at 800 °C, which was clearly elucidated by the HRTEM, XRD, and XPS measurements. The Fe-800 °C@BMC nanocatalyst showed excellent properties as an ORR electrocatalyst with an onset potential of 0.93 V vs RHE, keeping 90% of the initial current applied after the 20000s. Noticeably, the Fe-800 °C@BMC carbon-shell nanostructures delivered a Pt-like performance with a very low onset potential of −25 mV vs RHE, an overpotential of 75 mV at a current density of 10 mA cm −2 and an ultrahigh stability to keep the 99% of the initial current applied after 20000s, behaving like one of the most efficient HER core-shell structured non-precious electrocatalysts reported up to now. Also, the Fenton like catalytic studies revealed that the Fe-800 °C@BMC nanocatalyst was so far the most active catalyst for the degradation of tetracycline (TC) antibiotic allowing the degradation of 95.72% of TC in 45 min with a higher reaction rate constant of 0.068 min −1 . The impressive catalytic behavior of the Fe-800 °C@BMC nanocatalyst was attributed to the hierarchically porous carbon network as well as to the synergistic interaction between the encapsulated metallic iron core and the ultrathin carbon shell, which regulate the adsorption energy of the reactive species. The present work offers new insights into the development of scalable and high-performance tri-functional catalysts through a sustainable and low-cost synthetic route.