Bio-derived mesoporous carbon confinement synthesis of ultra-small α-Fe2O3 nanoparticles as electrocatalysts for overall water splitting

The use of high-surface-area materials in loading α-Fe₂O₃ nanoparticles presents an intriguing approach to improve the electrocatalytic efficiency of overall water splitting. Nevertheless, the effective management of α-Fe₂O₃ nanoparticle size to prevent their agglomeration continues to pose a significant challenge. This study used bio-based porous carbon with a specific surface area of 2876 m²/g and a mesoporous ratio of 95 % as a carrier to effectively disperse and inhibit the growth of α-Fe₂O₃ nanoparticles. The Fe₂O₃/NSC_-30 was synthesized using urea as a precipitant through an ethylene glycol-assisted hydrothermal method accompanied by high-temperature calcination, with the α-Fe₂O₃ nanoparticle size being approximately 5.5 nm. The synergistic effect between the ultra-small nanoparticles and the mesoporous structure facilitates the effective diffusion of electrolyte and exposes more catalytic active sites. The Fe₂O₃/NSC_-30 exhibited remarkable catalytic performance in the OER and HER, as evidenced by the respective low overpotentials of 270 mV and 250 mV at 20 mA cm⁻². Furthermore, when Fe₂O₃/NSC_-30 was utilized in the overall water-splitting reaction, a low cell voltage of 1.70 V was sufficient to achieve a current density of 20 mA cm⁻². In this study, a new method was proposed for loading ultra-small nanoparticles onto bio-derived mesoporous carbon for promoting overall water splitting with remarkable efficiency.