Ultra-high overpotential induces NiS2 deep reconstruction to significantly improve HER performance

It is well known that transition metal sulfides (TMS) (i.e., NiS 2 ) undergo electrochemical reconstructions to generate highly active Ni 3 S 2 during the process of hydrogen evolution reaction (HER) under overpotentials of < 500 mV. However, at higher overpotentials, Ni 3 S 2 can theoretically be further restructured into Ni and thus form Ni/Ni 3 S 2 heterogeneous interface structures, which may provide opportunities to further enhance HER activity of NiS 2 . Here, we selected NiS 2 as a model electrocatalyst and investigated the influence of the reconstruction results induced from regular to ultrahigh overpotentials on its electrocatalytic hydrogen precipitation performance. The experimental results showed that the most significant enhancement of hydrogen precipitation performance was obtained for the NiS 2 @CC-900 (900 means 900 mV overpotential) sample after the ultra-high overpotential induced reconstruction. Compared with the initial overpotential of 161 mV (10 mA cm –2 ), the overpotential of the reconstructed sample reduced by 67 mV (42%). The characterization results showed that an ultra-high overpotential of 900 mV induced deep reconstruction of NiS 2 , formed highly reactive Ni/Ni 3 S 2 heterogeneous interfaces, which is more conducive to improved HER performance and match well with theoretical calculations results. We demonstrated ultrahigh overpotential was an effective strategy to induce NiS 2 deeply reconstruction and significantly improve its HER performance, and this strategy was also applicable to CoS 2 and FeS 2 . This study provides an extremely simple and universal pathway for the reasonable construction of efficient electrocatalysts by induced TMS deeply reconstruction. This paper developed a simple yet effective method to significantly improve the HER performance of NiS 2 by ultrahigh overpotentials- induced deep electrochemical reconstructions. This simple strategy has good generalizability.