Highly efficient crystalline-amorphous Fe2O3/Fe-OOH oxygen evolution electrocatalysts reconstructed by FeS2 nanoparticles

It is crucial to explore the earth-abundant, high-efficient and stable electrocatalysts suitable for accelerating water splitting kinetics of oxygen evolution reaction (OER) in alkaline electrolytes. Herein, FexCo1-xS2 (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated via hydrothermal method and sulfidizing. Remarkably, the FeS2 delivers the most outstanding OER activity among prepared catalysts, with the overpotential of 240 mV for 10 mA/cm2, ultra-low Tafel slope of 45 mV/decades and high stability for 16 h. XRD, SEM, HRTEM, Raman and XPS characteristics before and OER process, TOF and electrochemical results indicate that surface reconstruction, strong combination of Fe-S and uniform dispersion of particles endow FeS2 with excellent catalytic property. The strong combination of Fe-S bond and uniform dispersion of FeS2 facilitates electron transfer. And the reconstructed crystalline-amorphous Fe2O3/FeOOH with rough surface may have a low energy barrier for the elementary reaction of O*→OOH*, which is responsible for boosting the generation of O2. In the practical two-electrode overall water splitting system in 1 M KOH, the FeS2/NF//Pt/C/NF system only needs an ultra-low cell voltage of 1.46 and 1.642 V to generate the current densities of 10 and 50 mA/cm2, respectively.