Hierarchical amorphous bimetallic sulfide nanosheets supported on Co-C nanofibers to synergistically boost water electrolysis

The design of a hierarchical heterostructure as a cost-effective and high-efficiency catalyst to realize electronic and interfacial engineering for the oxygen evolution reaction (OER) is a meaningful option in energy storage and conversion. In this work, amorphous NiFeS nanosheets supported on carbon nanofibers embedded with cobalt nanoparticles (Co-C/NiFeS nanofibers) catalysts are fabricated via the electro-spinning-carbonization-electrodeposition strategy. The optimized catalyst possesses a superior OER activity with a low overpotential of 233 mV at 10 mA cm−2 and a Tafel slope of 53.1 mV dec−1 in 1 mol L−1 KOH solution, together with a favorable hydrogen evolution reaction activity. Moreover, an alkaline Pt/C‖Co-C/NiFeS electrolyzer constructed with Co-C/NiFeS nanofibers as the anode and commercial Pt/C as the cathode achieves a low cell voltage of 1.48 V at 10 mA cm−2, which is superior to those of the benchmark Pt/C‖RuO2 cell and many other reported electrolyzers. As a bifunctional electrocatalyst, the Co-C/NiFeS‖Co-C/NiFeS electrolyzer can be assembled, exhibiting outstanding long-term stability of 70 h, which significantly outperforms that of the Pt/C‖RuO2 electrolyzer. The remarkable OER performance of the catalyst benefits from the distinct hierarchical heterostructure with Co-C nanofibers core and amorphous NiFeS nanosheets sheath and the generated highly conductive fibrous carbon substrate, endowing it with a large number of exposed active sites, great electrical conductivity and impregnable structural stability. Thus, this work demonstrates a facile and efficient approach to fabricate non-noble metal-based catalysts with superior electrocatalytic performance for practical energy conversion and storage.