Fe-doped CoS2 nanoparticles supported CoS2 microspheres@N-doped carbon electrocatalyst for enhanced oxygen evolution reaction

Non-noble electrocatalysts (such as transition metal sulfides) have been attractive to substitute noble-metal catalysts for oxygen evolution reaction (OER) to advance the practical application of clean energy. Herein, a Fe-doped CoS2 nanoparticles supported CoS2 microspheres@N-doped carbon (Fe-CoS2/CoS2@NC) is prepared as an efficient OER electrocatalyst. The Fe-CoS2/CoS2@NC composite is derived by sulfurizing the metanilic-intercalated Co(OH)2 microspheres decorated with binary active CoFe-Prussian blue analogue (CoFe-PBA) nanoparticles. The obtained composite combines the advantageous characteristics for enhancing electrocatalytic performances: binary active Fe-CoS2 derived from CoFe-PBA, active CoS2, N-doped carbon scaffold to improve electronic conductivity, the appropriate specific surface area and meso/macroporous size distribution to afford rich active sites. The Fe-CoS2/CoS2@NC requires an overpotential of 300 mV to reach a current density of 10 mA cm−2 with a Tafel slope of 72 mV dec−1 in 1.0 M KOH, outperforming those of NC/CoS2, NC/Fe-CoS2 and CoS2. Furthermore, the enhancement is experimentally supported by the low charge-transfer resistance and the large electrochemical active surface area during the OER. The synthesis approach could be extended to provide a tunable hydroxide/PBAs precursor-based approach for designing and preparing hierarchical structures as electrocatalysts.