Activating catalytic behavior of binary transition metal sulfide-shelled carbon nanotubes by iridium incorporation toward efficient overall water splitting

To meet the future demand for green energy, the development of catalysts for water splitting has become an essential task for scientists worldwide. In this context, a novel catalyst that relies on Ir-doped CoNi₂S₄ nanosheets assembled on carbon nanotubes, supported on three-dimensional carbon framework has been developed. The outstanding advantages of core-shell heterostructure and heteroatom doping are that they induce high abundance of exposed active sites and excellent ability for mass/charge transport of the catalyst. Thus, the catalyst provides excellent activity for hydrogen evolution reaction, which surpasses that of the noble-metal-free electrocatalysts reported in the literature. The catalyst also shows superior catalytic behavior for oxygen evolution reaction, which is even better than that of the commercial RuO₂ catalyst. Impressively, the electrolyzer using the proposed catalyst requires small cell voltages of only 1.60 V and 1.94 V at response current density of 10 mA/cm² and 50 mA/cm², respectively. More importantly, this electrolyzer manifests much better stability and durability than those of the electrolyzer using commercial Pt/C and RuO₂ catalysts.